Nasser N Peyghambarian

Interests

Research

His research interests include optical networks and optical communication, fiber optics, fiber lasers and amplifiers, organic photonics, 3d holographic display and 3D telepresence, nonlinear photonics, optical modulators and switches, laser spectroscopy, nanostructures and quantum dots.

Courses

Scholarly Contributions

Journals/Publications

• Peyghambarian, N. N. (2022). See attached file. See attached file.
• Peyghambarian, N. N. (2021). see attached file. see attached file.
• Peyghambarian, N. N. (2020). see attached file. see attached file.
• Peyghambarian, N. N. (2019). see attached file. see attached file.
• Peyghambarian, N. N. (2018). See attached file. See attached file.
• Peyghambarian, N. N. (2017). 5kW Near-diffraction-limited and 8kW High-brightness Monolithic Continuous Wave Fiber Lasers Directly Pumped by Laser Diodes. IEEE Photonics Journal, 9(5).
• Peyghambarian, N. N. (2017). A 100,000 Scale Factor Radar Range. Scientific Reports, 7.
• Peyghambarian, N. N. (2017). A new low-cost, compact, auto-phoropter for refractive assessment in developing countries. Scientific Reports, 7(13990).
• Peyghambarian, N. N. (2017). All-reflective multiphoton microscope. Optics Express, 25(19).
• Peyghambarian, N. N. (2017). Amplitude-Mode Spectroscopy of Charge Excitations in PTB7 pi-Conjugated Donor-Acceptor Copolymer for Photovoltaic Applications. Physical Review Applied, 7(6).
• Peyghambarian, N. N. (2017). General description and understanding of the nonlinear dynamics of mode-locked fiber lasers. Scientific Reports, 7(1).
• Peyghambarian, N. N. (2017). Pulsed Fluoride Fiber Lasers at 3 µm. Journal of the Optical Society of America B, 34(3).
• Peyghambarian, N. N. (2017). Rapid visualization of grain boundaries in monolayer MoS2 by multiphoton microscopy. Nature Communications, 8.
• Peyghambarian, N. N. (2017). Review of recent progress on single-frequency fiber lasers. Journal of the Optical Society of America B, 34(3).
• Peyghambarian, N. N. (2017). Ultra-strong nonlinear optical processes and trigonal warping in MoS2 layers. Nature Communications, 8.
• Peyghambarian, N. N. (2017). Yb3+-doped double-clad phosphate fiber for 976 nm single-frequency laser amplifiers. Optical Materials Express, 7(4).
• Peyghambarian, N. N. (2016). see attached. see attached.
• Peyghambarian, N. N. (2015). see attachment. see attachment.
• Lau, P. C., Norwood, R. A., Mansuripur, M., & Peyghambarian, N. N. (2014). An effective nanosensor for organic molecules based on water-soluble mercaptopropionic acid-capped CdTe nanocrystals with potential application in high-throughput screening and high-resolution optical microscopy. Biomedical Optics Express, 5, 2420-2434.
• Lynn, B., Blanche, P., & Peyghambarian, N. (2014). Photorefractive polymers for holography. Journal of Polymer Science, Part B: Polymer Physics, 52(3), 193-231.
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  Abstract: This review describes the current state-of-the-art of photorefractive polymers for holography. The analysis of this rich field begins with a brief historical perspective followed by descriptions of prevailing physical models relating basic parameters of the polymer constituents to the bulk response of the final device. Methods for probing these responses and the underlying phenomena are discussed followed by an overview of the recent holographic applications of photorefractive polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 193-231 Photorefractive polymers are a unique material in which a holographic grating can be recorded and rewritten without pre- or postprocessing. This review describes the physical theory and various applications of photorefractive polymers and devices within the current scientific landscape. Copyright © 2013 Wiley Periodicals, Inc.
• Peng, X., Kim, K., Mielke, M., Jennings, S., Masor, G., Stohl, D., Chavez-Pirson, A., Nguyen, D. T., Rhonehouse, D., Zong, J., Churin, D., & Peyghambarian, N. (2014). Monolithic fiber chirped pulse amplification system for millijoule femtosecond pulse generation at 1.55 μm. Optics Express, 22(3), 2459-2464.
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  Abstract: A monolithic fiber chirped pulse amplification system that generates sub-500 fs pulses with 913 μJ pulse energy and 4.4 W average power at 1.55 μm wavelength has recently been demonstrated. The estimated peak power for the system output approached 1.9 GW. The pulses were near diffraction-limited and near transform-limited, benefiting from the straight and short length of the booster amplifier as well as adaptive phase shaping for the overall mitigation of the nonlinear phase accumulation. The booster amplifier employs an Er 3+-doped large mode area high efficiency media fiber just 28 cm in length with a fundamental mode (LP01) diameter of 54 μm and a corresponding effective mode area of 2290 μm2. © 2014 Optical Society of America.
• Peyghambarian, N. N. (2014). see attachment. see attachment.
• Zhu, X., Zong, J., Wiersma, K., Norwood, R. A., Prasad, N. S., Obland, M. D., Chavez-Pirson, A., & Peyghambarian, N. (2014). Watt-level short-length holmium-doped ZBLAN fiber lasers at 1.2 μm. Optics Letters, 39(6), 1533-1536.
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  Abstract: In-band core-pumped Ho3+-doped ZBLAN fiber lasers at the 1.2 μm region were investigated with different gain fiber lengths. A 2.4W1190 nm all-fiber laser with a slope efficiency of 42% was achieved by using a 10 cm long gain fiber pumped at a maximum available 1150 nm pump power of 5.9 W. A 1178 nm all-fiber laser was demonstrated with an output power of 350 mW and a slope efficiency of 6.5%. High Ho3+ doping in ZBLAN is shown to be effective in producing single-frequency fiber lasers and short-length fiber amplifiers immune from stimulated Brillouin scattering. © 2014 Optical Society of America.
• Himmelhuber, R., Herrera, O. D., Li, L. i., Jones, A., Norwood, R. A., & Peyghambarian, N. (2013). A silicon-polymer hybrid modulator - Simulation and proof of principle. 2013 Optical Interconnects Conference, OI 2013, 88-89.
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  Abstract: Optimal dimensions are found for the silicon waveguide in an electro-optic (EO) polymer cladding-based silicon waveguide modulator. The confinement factor as well as the effective index of the mode are taken into account. With the optimal 275 nm waveguide width and 4 μm electrode spacing, Vπ of a few volts can be achieved even with low Γ33 EO polymers. © 2013 IEEE.
• Himmelhuber, R., Herrera, O. D., Voorakaranam, R., Li, L. i., Jones, A. M., Norwood, R. A., Luo, J., Jen, A. K., & Peyghambarian, N. (2013). A silicon-polymer hybrid modulator-design, simulation and proof of principle. Journal of Lightwave Technology, 31(24), 4067-4072.
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  Abstract: Optimal dimensions are found for the silicon waveguide in an electro-optic (EO) polymer cladding-based silicon waveguide modulator. The confinement factor as well as the effective index of the mode are taken into account. The influence of the coplanar electrode spacing and electrode height on performance are examined and a figure of merit formula for choosing the optimal device geometry is shown. The design space for both 1550 nm and 1310 nm wavelengths is explored. With the optimal 275 nm waveguide width and 4 μm electrode spacing, a V \pi of a few volts can be achieved even with moderate r33 EO polymers. Experimental results on a fabricated modulator are shown and compared with the predicted performance. © 2013 IEEE.
• Hofmann, P., Amezcua-Correa, R., Antonio-Lopez, E., Ott, D., Segall, M., Divliansky, I., Lumeau, J., Glebova, L., Glebov, L., Peyghambarian, N., & Schülzgen, A. (2013). Strong bragg gratings in highly photosensitive photo-thermo-refractive- glass optical fiber. IEEE Photonics Technology Letters, 25(1), 25-28.
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  Abstract: A new type of photosensitive fiber is demonstrated. Long lengths (> 100m) of coreless optical fiber are fabricated from highly photosensitive photo-thermo-refractive glass. A minimum loss of < 2 dB m is measured. A holographic technique using low power near-UV two-beam interference patterns is applied to record strong and robust Bragg gratings inside the fiber. The gratings show no degradation when heated up to 425°C for several hours. © 2012 IEEE.
• Hofmann, P., Voigtländer, C., Nolte, S., Peyghambarian, N., & Schülzgen, A. (2013). 550-mW output power from a narrow linewidth all-phosphate fiber laser. Journal of Lightwave Technology, 31(5), 756-760.
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  Abstract: We present a compact monolithic all-phosphate glass fiber laser with up to 550 mW of output power operating on a single longitudinal mode. We measured a linewidth of less than 60 kHz and relaxation oscillation peak amplitudes below -100 dB/Hz without active RIN-supression. The laser cavity has been formed by inscribing fiber Bragg gratings (FBG) directly into heavily Er 3+Yb3+ doped phosphate glass fiber using femtosecond laser pulses and a phasemask. The compact form factor and higher output power combined with the low noise and narrow line width characteristic make this laser an ideal candidate for ranging, interferometry and sensing applications. © 2012 IEEE.
• Khosroabadi, A. A., Gangopadhyay, P., Duong, B., Thomas, J., Sigdel, A. K., Berry, J. J., Gennett, T., Peyghambarian, N., & Norwood, R. A. (2013). Fabrication, electrical and optical properties of silver, indium tin oxide (ITO), and indium zinc oxide (IZO) nanostructure arrays. Physica Status Solidi (A) Applications and Materials Science, 210(5), 831-838.
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  Abstract: In thin film devices such as light-emitting diodes, photovoltaic cells and field-effect transistors, the processes of charge injection, charge transport, charge recombination, separation and collection are critical to performance. Most of these processes are relevant to nanoscale metal and metal oxide electrode-organic material interfacial phenomena. In this report we present a unique method for creating tailored one-dimensional nanostructured silver, tin and/or zinc substituted indium oxide electrode structures over large areas. The method allows production of high aspect ratio nanoscale structures with feature sizes below 100 nm and a large range of dimensional tunability. We observed that both the electronic and optical properties of these electrodes are closely correlated to the nanostructure dimensions and can be easily tuned by control of the feature size. Surface area enhancement accurately describes the conductivity studies, while nanostructure dependent optical properties highlight the quasi-plasmonic nature of the electrodes. Optimization of the nanostructured electrode transparency and conductivity for specific opto-electronic systems is expected to provide improvement in device performance. A versatile and powerful new method has been developed that enables the lithographic fabrication of nano-architectured ordered 2D metal and metal-oxide electrodes. Optical band gap, electronic carrier concentrations and resistivity of these highly transparent electrodes can be tuned by simply changing the dimensions of the unit nanostructures. Fabrication, electrical and optical properties of indium tin oxide, indium zinc oxide and silver electrodes are discussed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
• Liebig, C. M., Basun, S., Buller, S. S., Evans, D. R., Banerjee, P. P., Blanche, P. A., Christensen, C. W., Peyghambarian, N., & Thomas, J. (2013). Enhanced gain dynamics in photorefractive polymers. Proceedings of SPIE - The International Society for Optical Engineering, 8847.
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  Abstract: The complexity of photorefractive polymers arises from multiple contributions to the photo-induced index grating. Analysis of the time dynamics of the two-beam coupling signal is used to extract information about the charge species responsible for the grating formation. It has been shown in a commonly used photorefractive polymer at moderate applied electric fields, the primary charge carriers (holes) establish an initial grating which, however, are followed by a subsequent competing grating (electrons) that decreases the two-beam coupling efficiency. We show by upon using higher applied bias fields, gain enhancement can be achieved by eliminating the electron grating contribution and returning to hole gratings only. © 2013 SPIE.
• Liebig, C. M., Buller, S. H., Banerjee, P. P., Basun, S. A., Blanche, P. -., Thomas, J., Christenson, C. W., Peyghambarian, N., & Evans, D. R. (2013). Achieving enhanced gain in photorefractive polymers by eliminating electron contributions using large bias fields. Optics Express, 21(25), 30392-30400.
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  Abstract: Photorefractive polymers have been extensively studied for over two decades and have found applications in holographic displays and optical image processing. The complexity of these materials arises from multiple charge contributions, for example, leading to the formation of competing photorefractive gratings. It has been recently shown that in a photorefractive polymer at relatively moderate applied electric fields the primary charge carriers (holes) establish an initial grating, followed by a subsequent competing grating (electrons) resulting in a decreased two-beam coupling and diffraction efficiencies. In this paper, it is shown that with relatively large sustainable bias fields, the two-beam coupling efficiency is enhanced owing to a decreased electron contribution. These results also explain the cause of dielectric breakdown experienced under large bias fields. Our conclusions are supported by self-pumped transient two-beam coupling and photocurrent measurements as a function of applied bias fields at different wavelengths. © 2013 Optical Society of America.
• Lopez-Santiago, A., Gangopadhyay, P., Bablumyan, A., Voorakaranam, R., Takeuchi, K., Deohazer, D. J., Norwood, R. A., & Peyghambarian, N. (2013). Polarization independent and low loss laser written polysiloxane interconnect building blocks. 2013 Optical Interconnects Conference, OI 2013, 66-67.
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  Abstract: Single-mode polysiloxane based waveguides and directional couplers, key optical interconnect building blocks, were fabricated using direct laser writing. Key performance parameters include polarization independent propagation loss of 0.23 dB/cm and a possible wafer scale fabrication. © 2013 IEEE.
• Mait, J. N., Mendez, E., Peyghambarian, N., & Poon, T. -. (2013). Applied optics golden anniversary commemorative reviews: Introduction. Applied Optics, 52(1), CR1-CR3.
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  Abstract: Applied Optics presents three special issues to end its retrospective of Applied Optics' 50 years. The special issues are interference, interferometry, and phase; imaging, optical processing, and telecommunications; and polarization and scattering. The issues, which contain 19 commemorative reviews from some of the journal's luminaries, are summarized. © 2012 Optical Society of America.
• Nagel, J., Temyanko, V., Dobler, J., Salganskii, M., Likhachev, M., Alexeev, V., Bubnov, M., Dianov, E., Norwood, R., & Peyghambarian, N. (2013). Phosphosilicate Raman gain fibers with varying core concentration for enhanced SBS suppression. 2013 IEEE Photonics Conference, IPC 2013, 271-272.
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  Abstract: New SBS suppressed phosphosilicate Raman gain fibers are demonstrated with longitudinally varying core doping concentrations. Peak Brillouin gain is reduced by 6 dB over standard fibers resulting in a 2.8 dB increase in amplified power. © 2013 IEEE.
• Peng, X., Kim, K., Mielke, M., Jennings, S., Masor, G., Stohl, D., Chavez-Pirson, A., Nguyen, D. T., Rhonehouse, D., Zong, J., Churin, D., & Peyghambarian, N. (2013). High efficiency, monolithic fiber chirped pulse amplification system for high energy femtosecond pulse generation. Optics Express, 21(21), 25440-25451.
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  PMID: 24150384;Abstract: A novel monolithic fiber-optic chirped pulse amplification (CPA) system for high energy, femtosecond pulse generation is proposed and experimentally demonstrated. By employing a high gain amplifier comprising merely 20 cm of high efficiency media (HEM) gain fiber, an optimal balance of output pulse energy, optical efficiency, and B-integral is achieved. The HEM amplifier is fabricated from erbium-doped phosphate glass fiber and yields gain of 1.443 dB/cm with slope efficiency >45%. We experimentally demonstrate near diffraction-limited beam quality and near transform-limited femtosecond pulse quality at 1.55 μm wavelength. With pulse energy >100 μJ and pulse duration of 636 fs (FWHM), the peak power is estimated to be ∑160 MW. NAVAIR Public Release Distribution Statement A-"Approved for Public release; distribution is unlimited". © 2013 Optical Society of America.
• Peyghambarian, N., Herrera, O. D., Schneebeli, L., Kieu, K., Norwood, R. A., & Peyghambarian, N. N. (2013). Slow light based on stimulated Raman scattering in an integrated liquid-core optical fiber filled with CS2. Optics express, 21(7).
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  We demonstrate a fiber-based slow light system using a carbon disulfide (CS2)) filled integrated liquid-core optical fiber (i-LCOF). Using 1 meter of i-LCOF we were able to delay 18ps pulses up to 34ps; a delay of 188% of the pulse width. This experimental setup serves as a foundation for slow-light experiments in other nonlinear liquids. Numerical simulations of pulse-propagation equations confirmed the observed delay and a simplified method is presented that can be applied to calculate induced delay for non-cw Stokes pulses. The system is all-fiber and compact with delays greater than a pulse width, indicating potential application as an ultrafast controllable delay line for time division multiplexing in multiGb/s telecommunication systems.
• Peyghambarian, N., Kieu, K., Churin, D., Schneebeli, L., Norwood, R. A., & Peyghambarian, N. N. (2013). Brillouin lasing in integrated liquid-core optical fibers. Optics letters, 38(4).
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  We report Brillouin lasing in an integrated liquid-core optical fiber filled with neat CS2. This is the first observation of Brillouin lasing in an optical fiber filled with a liquid, to the best of our knowledge. The linewidth of the single frequency liquid-based Brillouin laser was estimated to be
• Peyghambarian, N., Lau, P. C., Norwood, R. A., Mansuripur, M., & Peyghambarian, N. N. (2013). An effective and simple oxygen nanosensor made from MPA-capped water soluble CdTe nanocrystals. Nanotechnology, 24(1).
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  CdTe semiconductor nanocrystals (NCs) with 3-mercaptopropionic acid as the ligand exhibit a reversible response towards inter-switching oxygen and argon environments. The photoluminescence response is investigated at multiple oxygen concentrations, NC coverage and excitation intensities, in which all conditions exhibit full recovery upon exposure to flowing argon. The CdTe NC's large surface-to-volume ratio results in high sensitivity towards oxygen molecules with significant photoluminescence quenching at a concentration of 40 ppm. This suggests a novel approach to the creation of simple, inexpensive and ultrasensitive oxygen nanosensors.
• Peyghambarian, N., Wei, C., Zhu, X., Wang, F., Xu, Y., Balakrishnan, K., Song, F., Norwood, R. A., & Peyghambarian, N. N. (2013). Graphene Q-switched 2.78 μm Er3+-doped fluoride fiber laser. Optics letters, 38(17).
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  We report a diode-pumped 2.78 μm Er3+-doped ZBLAN fiber laser passively Q switched by a graphene saturable absorber, which was directly deposited onto a fiber dichroic mirror by the method of optically driven deposition. Stable Q-switched operation with a pulse duration of 2.9 μs and a pulse energy of 1.67 μJ was achieved in a 10 m long gain fiber. The pulse duration was reduced to 1 μs when the gain fiber length was shortened to 2 m. This Letter demonstrates that graphene is a promising and reliable saturable absorber for mid-infrared pulse generation at 3 μm.
• Tian, M., Ping, L. u., Chen, L., Liao, H., Liu, D., Peyghambarian, N., & Zhang, J. (2013). Plasmon hybridization in stacked nanorods dimer. Optics Communications, 311, 20-25.
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  Abstract: In this paper, we investigate the coupling effects of three dimensional Au nanorods dimer. Structural arrangement determines the electromagnetic properties of matter. Plasmon hybridization theory can explain the mode split phenomenon. A theoretical model based on a Langrangian formalism is used to interpret the evolution of the coupling effects as a function of twist angle which demonstrate that the optical properties of these Au nanorod dimers can be substantially modified by altering the twist angles between the two rods, arising from the variation of electromagnetic interactions between them. Furthermore, it shows that the dependence of the resonance frequencies and the frequency gap on the distance between two rods. We find that by increasing the twist angle or the distance between two rods, the two resonance branches tend to converge. Last, we use the 3D-finite-difference time-domain (FDTD) method to do numerical simulation, which reveals that the theoretical model can quantitatively corroborate the results from the numerical simulations. © 2013 Published by Elsevier B.V.
• Wei, C., Zhu, X., Norwood, R. A., Song, F., & Peyghambarian, N. (2013). Numerical investigation on high power midinfrared supercontinuum fiber lasers pumped at 3 μm. Optics Express, 21(24), 29488-29504.
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  Abstract: High power mid-infrared (mid-IR) supercontinuum (SC) laser sources in the 3-12 μm region are of great interest for a variety of applications in many fields. Although various mid-IR SC laser sources have been proposed and investigated experimentally and theoretically in the past several years, power scaling of mid-IR SC lasers beyond 3 μm with infrared edges extending beyond 7 μm are still challenges because the wavelengths of most previously used pump sources are below 2 μm. These problems can be solved with the recent development of mode-locked fiber lasers at 3 μm. In this paper, high power mid-IR SC laser sources based on dispersion engineered tellurite and chalcogenide fibers and pumped by ultrafast lasers at 3 μm are proposed and investigated. Our simulation results show that, when a W-type tellurite fiber with a zero dispersion wavelength (ZDW) of 2.7 μm is pumped at 2.78 μm, the power proportion of the SC laser beyond 3 μm can exceed 40% and the attainable SC output power of the proposed solid-cladding tellurite fiber is one order of magnitude higher than that of existing microstructured tellurite fibers. Our calculation also predicts that a very promising super-broadband mid-IR SC fiber laser source covering two atmospheric windows and molecules' "fingerprint" region can be obtained with a microstructured As 2Se3 chalcogenide fiber pumped at 2.78 μm. © 2013 Optical Society of America.
• Xiong, L., Hofmann, P., Schülzgen, A., Peyghambarian, N., & Albert, J. (2013). Deep UV-induced near-infrared photodarkening of Er/Yb-doped and undoped phosphate fibers. Optics Letters, 38(20), 4193-4196.
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  PMID: 24321957;Abstract: Photodarkening (PD) of Er/Yb-doped and undoped phosphate fibers caused by pulsed 193 nm irradiation from an ArF excimer laser to form Bragg grating mirrors is investigated. Doped and undoped phosphate fibers exhibit the same level of significant UV-induced PD loss, which is associated with the formation of a color center band at 467 nm. The UV-induced absorption extends into the NIR and creates a loss on the order of 1 dB/cm across the C-band. Photo-bleaching by a high-power supercontinuum source, and thermal-bleaching processes are performed on photodarkened samples. Both bleaching processes are found effective to fully erase the UV-induced PD loss. © 2013 Optical Society of America.
• Zhu, X., Shi, W., Zong, J., Nguyen, D., Norwood, R. A., Chavez-Pirson, A., & Peyghambarian, N. (2013). Single-frequency ytterbium-doped fiber laser at 976 nm. Proceedings of SPIE - The International Society for Optical Engineering, 8601.
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  Abstract: Linearly polarized wavelength stable single frequency ytterbium (Yb 3+) doped fiber lasers below 1 μm, namely threelevel Yb 3+ fiber lasers, are highly demanded for nonlinear wavelength conversion to generate coherent blue light or even deep ultraviolet coherent sources. We present performance of a 976 nm single-frequency core-pumped distributed Bragg reflector (DBR) fiber laser consisting of a 2-cm long highly ytterbium-doped phosphate fiber and a pair of silica fiber Bragg gratings (FBGs) and their use for frequency doubling experiment. The high reflection (HR > 99%) and partial reflection (PR = 60%) FBGs were cleaved very close to the index modulation region and directly spliced to a 2-cm-long highly Yb 3+-doped phosphate fiber. Over 100 mW of linearly polarized output with a linewidth less than 2 kHz can be obtained when the launched pump power is about 450 mW. The efficiency of the 976 nm single-frequency fiber laser (the output power vs the launched pump power) is about 25%. The relative intensity noise was measured to be -110 dB/Hz at 1 MHz and the variation of the center wavelength is less than 0.0005 nm during a measurement period of 2.5 hours. This single-frequency fiber laser has an SNR of over 50 dB and there is no strong ASE or spurious lasing at long wavelengths even at the maximum pump power. This all-fiber single-frequency DBR laser with attractive features can be used for efficient blue and UV generation through nonlinear frequency conversion. Moreover, this high-performance 976 nm single-frequency fiber laser can be used as a single-frequency, low RIN pump laser for long wavelength Yb3+-, Er3+-, or Yb3+/Er3+-doped fiber lasers and amplifiers. © 2013 Copyright SPIE.
• Zhu, X., Zhu, G., Shi, W., Zong, J., Wiersma, K., Nguyen, D., Norwood, R. A., Chavez-Pirson, A., & Peyghambarian, N. (2013). 976 nm single-polarization single-frequency ytterbium-doped phosphate fiber amplifiers. IEEE Photonics Technology Letters, 25(14), 1365-1368.
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  Abstract: Core-pumped 976 nm single-polarization singlefrequency fiber amplifiers based on several centimeter long polarization maintaining 6 wt% ytterbium (Yb3+) doped phosphate fibers are investigated experimentally and numerically. A 350 mW linearly polarized output with > 20 dB polarization extinction ratio and > 50 dB optical signal-to-noise ratio is obtained from a 4 cm fiber amplifier at maximum available pump power of 793 mW. The slope efficiency of the 4 cm fiber amplifier is 52.5%. A small signal net gain of 25 dB, corresponding to a unit gain of over 6 dB/cm is achieved in this fiber. It is predicted that a watt level 976 nm core-pumped fiber amplifier can be achieved using more powerful pumps and low insertion loss optical components. © 1989-2012 IEEE.
• Zhu, X., Zong, J., Miller, A., Wiersma, K., Norwood, R. A., Prasad, N. S., Chavez-Pirson, A., & Peyghambarian, N. (2013). Single-frequency, single-polarization holmium-doped ZBLAN fiber laser. Proceedings of SPIE - The International Society for Optical Engineering, 8601.
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  Abstract: We present the performance of a single frequency, single-polarization holmium (Ho3+)-doped ZBLAN (ZrF4-BaF2-LaF 3-AlF3-NaF) fiber laser at 1200 nm. This distributed Bragg reflector (DBR) fiber laser was developed by splicing a 22 mm long highly Ho3+-doped ZBLAN fiber to a pair of silica fiber Bragg gratings (FBG). The successful fusion splicing of silica fiber to ZBLAN fiber, with their very different melting temperatures, was accomplished by using NP Photonics proprietary splicing technique. The 3 mol% Ho3+-doped ZBLAN fiber had a core diameter of 6.5 μm and a cladding diameter of 125 μm. The threshold of this laser was seen to be about 260 mW, and when the pump power was 520 mW, the output power was about 10 mW. The efficiency of the 1200 nm single-frequency fiber laser, i.e. the ratio of the output power to the launched pump power, was about 3.8%. The linewidth of the 1200 nm single-frequency fiber laser was estimated to be about 100 kHz by comparing the measured frequency noise of the 1200 nm single-frequency fiber laser with that of 1 μm NP Photonics single-frequency fiber lasers whose linewidths have been measured to be in the 1- 10 kHz range. The relative intensity noise of this DBR all-fiber laser was measured to be < 110 dB/Hz at the relaxation oscillation peak and the polarization extinction ratio was measured to be > 19 dB. Due to its low phonon energy and long radiative lifetimes, rare-earth-doped ZBLAN allows various transitions that are typically terminated in silica glass, resulting in ultraviolet, visible, and infrared rare-earth doped ZBLAN lasers. Therefore, our results highlight the exciting prospect that the accessible wavelength range of single-frequency DBR fiber lasers can be expanded significantly by using rare-earth-doped ZBLAN fibers. © 2013 Copyright SPIE.
• Banerjee, P. P., Buller, S. H., Liebig, C. M., Basun, S. A., Cook, G., Evans, D. R., Blanche, P. -., Thomas, J., Christenson, C. W., & Peyghambarian, N. (2012). Time dynamics of self-pumped reflection gratings in a photorefractive polymer. Journal of Applied Physics, 111(1).
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  Abstract: The time dynamics of self-pumped reflection gratings in a commonly used photorefractive polymer PDCST:PVK:ECZ-BBP:C 60 with no additional electron sources or traps is investigated. While holes are normally the mobile charges and responsible for grating formation, our experimental observations, analyzed using multi-exponential fitting curves, show evidence of electrons in addition to holes as charge carriers, particularly above an applied field of 40 V/μm. The dependence of effective carrier mobilities on the applied electric field, deduced from experimental results, show stronger field dependence of electron mobility at high electric fields. At an applied field of 70 V/μm, electron and hole mobilities become approximately equal, and the contribution of electrons on grating formation becomes significant. © 2012 American Institute of Physics.
• Gangopadhyay, P., Lopez-Santiago, A., Grant, H. R., Peyghambarian, N., & Norwood, R. A. (2012). New materials for magneto optic in-fiber and waveguide isolators. Advances in Optical Materials, AIOM 2012, IF2A.3.
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  Abstract: We report recent advances in synthesis of new magneto-optic materials including novel colorless magnetic ionic liquids and magnetic nanoparticles core polymer shell nanocomposites for in-fiber and waveguide based non-reciprocal operation for optical isolation and circulation. © 2012 OSA.
• Hofmann, P., Mafi, A., Jollivet, C., Tiess, T., Peyghambarian, N., & Schülzgen, A. (2012). Detailed investigation of mode-field adapters utilizing multimode-interference in graded index fibers. Journal of Lightwave Technology, 30(14), 2289-2297.
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  Abstract: We present a detailed study of mode-field adapters (MFA) based on multimode interference in graded index multimode fibers. We have fabricated and characterized MFAs from a selection of commercially available single-mode and graded index fibers. Compared to existing techniques, the presented MFAs can be fabricated very quickly and are not limited to certain fiber types. Insertion losses of $< 0.5$ dB over a spectral range of several hundred nanometers have been obtained, which is comparable or better than the industry standard. © 2012 IEEE.
• Hofmann, P., Mafi, A., Jollivet-Salvin, C., Tiess, T., Peyghambarian, N., & Schülzgen, A. (2012). Low-loss, broad-band coupling between single-mode optical fibers with very different mode-field diameters. 2012 Conference on Lasers and Electro-Optics, CLEO 2012.
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  Abstract: An approach for efficient coupling between different single-mode fibers is demonstrated. It is shown that short segments of graded-index fiber can provide broadband, extremely low-loss coupling even when the fibers have very different mode-field diameters. © 2012 OSA.
• Hofmann, P., Mafi, A., Jollivet-Salvin, C., Tiess, T., Peyghambarian, N., & Schülzgen, A. (2012). Low-loss, broad-band coupling between single-mode optical fibers with very different mode-field diameters. CLEO: Science and Innovations, CLEO_SI 2012, CM1N.4.
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  Abstract: An approach for efficient coupling between different single-mode fibers is demonstrated. It is shown that short segments of graded-index fiber can provide broadband, extremely low-loss coupling even when the fibers have very different mode-field diameters. © OSA 2012.
• Khoury, J., Donoghuec, J., Haji-saeed, B., Woods, C. L., Kierstead, J., Peyghambarian, N., & Yamamoto, M. (2012). Optical deconvolution and correlation characterization via dynamic range compression using organic photorefractive materials. Frontiers in Optics, FIO 2012.
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  Abstract: In this paper, we demonstrate image restoration and recognition via photorefractive two-beam coupling using Nitto Denko/Arizona University organic photorefractive materials. Our experimental of two-beam coupling hardware recognition outperforms the software simulations based on the phase-only and some optimal correlation filters. © OSA 2012.
• Lopez-Santiago, A., Grant, H. R., Gangopadhyay, P., Voorakaranam, R., Norwood, R. A., & Peyghambarian, N. (2012). Cobalt ferrite nanoparticles polymer composites based all-optical magnetometer. Optical Materials Express, 2(7), 978-986.
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  Abstract: A method has been developed to prepare cobalt ferrite particle core polymer shell nanoparticles. These engineered nanoparticles can be further embedded into a polymer host matrix to develop highly transparent polymer based magneto-optic materials. A proof-of-principle all-optical magnetometer has been constructed based on the cobalt ferrite core polymer shell based nanocomposite material. A noise equivalent magnetic field sensitivity of 50nT/vHz was observed using a 3μT 500Hz control magnetic field. © 2012 Optical Society of America.
• Mafi, A., Hofmann, P., Salvin, C. J., Peyghambarian, N., & Schülzgen, A. (2012). Low-loss coupling between single-mode optical fibers with very different mode-field diameters. Optics InfoBase Conference Papers.
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  Abstract: We show that short segments of graded-index optical fiber can provide broadband, very low-loss coupling between single-mode optical fibers with very different mode-field diameters. ©2012 Optical Society of America.
• Nagel, J. A., Temyanko, V., Norwood, R. A., Peyghambarian, N., Dobler, J. T., Dianov, E. M., Biriukov, A. S., & Sysoliatin, A. A. (2012). Raman amplification of a narrow linewidth continuous wave signal for spectroscopic remote sensing applications using longitudinally varying core fibers. Fiber Lasers and Applications, FILAS 2012.
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  Abstract: We report on the development of a Raman amplifier using fibers with longitudinally varying cores. Approximately 3.0W of a 1.26μm narrow linewidth continuous wave signal has been demonstrated for remote sensing of atmospheric oxygen levels. © 2011 Optical Society of America.
• Petersen, E., Shi, W., Chavez-Pirson, A., & Peyghambarian, N. (2012). High peak-power single-frequency pulses using multiple stage, large core phosphate fibers and preshaped pulses. Applied Optics, 51(5), 531-534.
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  PMID: 22330284;Abstract: We have developed a monolithic high power pulsed fiber laser in a master oscillator power amplifier (MOPA) configuration, which is capable of reaching 0.38 mJ pulse energy and 128 kW peak power for 3 ns pulses at ?1550 nm while maintaining transform-limited linewidth. The fiber laser pulse seed was achieved by directly modulating a CW single-frequency fiber laser using an electro-optic modulator. We used an arbitrary waveform generator to preshape the fiber laser pulses before amplification to avoid pulse steepening and dynamic gain saturation. Single-mode, polarization maintaining highly Er?Yb codoped large core phosphate fibers were used in the power amplifier stages to scale the transform-limited fiber laser pulses, avoiding any nonlinearities. © 2012 Optical Society of America.
• Peyghambarian, N., Kieu, K., Schneebeli, L., Merzlyak, E., Hales, J. M., DeSimone, A., Perry, J. W., Norwood, R. A., & Peyghambarian, N. N. (2012). All-optical switching based on inverse Raman scattering in liquid-core optical fibers. Optics letters, 37(5).
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  We report on a new platform for all-optical switching based on inverse Raman scattering in liquids. Narrowband switching, which could be suitable for wavelength-division-multiplexed applications, is demonstrated using integrated liquid-core optical fiber infiltrated with both neat liquids (CCl(4) and CS(2)) as well as an organic chromophore (β-carotene) dissolved in CCl(4). Compared to standard glass optical fibers, these liquids have much larger Raman loss coefficients, which help reduce the pump power by at least an order of magnitude. Further improvements can be expected with the development of highly soluble organic compounds possessing large Raman cross sections.
• Peyghambarian, N., Kieu, K., Schneebeli, L., Norwood, R. A., & Peyghambarian, N. N. (2012). Integrated liquid-core optical fibers for ultra-efficient nonlinear liquid photonics. Optics express, 20(7).
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  We have developed a novel integrated platform for liquid photonics based on liquid core optical fiber (LCOF). The platform is created by fusion splicing liquid core optical fiber to standard single-mode optical fiber making it fully integrated and practical - a major challenge that has greatly hindered progress in liquid-photonic applications. As an example, we report here the realization of ultralow threshold Raman generation using an integrated CS₂ filled LCOF pumped with sub-nanosecond pulses at 532 nm and 1064 nm. The measured energy threshold for the Stokes generation is 1nJ, about three orders of magnitude lower than previously reported values in the literature for hydrogen gas, a popular Raman medium. The integrated LCOF platform opens up new possibilities for ultralow power nonlinear optics such as efficient white light generation for displays, mid-IR generation, slow light generation, parametric amplification, all-optical switching and wavelength conversion using liquids that have orders of magnitude larger optical nonlinearities compared with silica glass.
• Peyghambarian, N., Wei, C., Zhu, X., Norwood, R. A., & Peyghambarian, N. N. (2012). Passively continuous-wave mode-locked Er(3+)-doped ZBLAN fiber laser at 2.8 μm. Optics letters, 37(18).
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  An Er(3+)-doped ZrF(4)-BaF(2)-LaF(3)-AlF(3)-NaF (ZBLAN) fiber laser was passively mode-locked by inserting a Fe(2+):ZnSe crystal into the free space part of the cavity. Continuous-wave mode-locked pulses at 2.8 μm with a pulse duration of 19 ps estimated from the spectral bandwidth and an average power of 51 mW were generated when a collimated beam traversed the Fe(2+):ZnSe crystal, while Q-switched mode-locked pulses were obtained when the Fe(2+):ZnSe crystal was illuminated by the focused beam.
• Shi, W., Petersen, E. B., Fang, Q., Kieu, Q., Chavez-Pirson, A., Peyghambarian, N., & Jirong, Y. u. (2012). MJ-level 2μm transform-limited nanosecond pulses based on highly Tm-doped germanate fibers. Fiber Lasers and Applications, FILAS 2012.
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  Abstract: We report a monolithic ~ 0.95 mJ pulsed fiber laser in 2 μm regime with transformlimited linewidth and 10-100 ns pulse width. This MOPA-based pulsed fiber laser is based on highly Tm-doped germanate fibers. © 2012 OSA.
• Tian, M., Ping, L. u., Chen, L., Liu, D., & Peyghambarian, N. (2012). Plasmonic Bragg reflectors based on metal-embedded MIM structure. Optics Communications, 285(24), 5122-5127.
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  Abstract: We propose and investigate a metalembedded metal-insulator-metal (MIM) structure plasmonic Bragg reflector (PBR) using the finite-difference time-domain (FDTD) method with PMLs (perfectly matched layers) boundary conditions. It improves the performance of conventional step profile MIM PBRs to some extent. Our numerical study reveals that the metal-embedded PBRs exhibit lower insertion loss, narrower bandgap, and reduced rippling in the transmission spectrum when compared with the step PBRs at the same normalized index contrast and transmission levels. The defect mode of the metal-embedded PBRs also exhibits higher transmission. To suppress the sidelobes in the transmission spectrum, we further smooth the end of the embedded metal, which demonstrates a better performance. Then, we find with respect to the Bragg wavelength, the longer wavelengths have a tendency to spread in the wider regions of the insulator layer; however, the shorter wavelengths have a tendency to spread in the embedded metal regions. The apodized PBRs with the embedded metal length decreasing (increasing) efficaciously suppress the ripples at the right (left) band edges. Then, we use the impedance theoretical model to explain this phenomenon. Finally, we realize a flat-top transmission band filter by connecting two apodized PBRs, and the band and center wavelength can be adjusted. © 2012 Elsevier B.V. All rights reserved.
• Wei, C., Zhu, X., Norwood, R. A., & Peyghambarian, N. (2012). Er³⁺-doped ZBLAN fiber laser Q-switched by Fe: ZnSe. CLEO: Applications and Technology, CLEO_AT 2012, JW2A.61.
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  Abstract: A highly erbium ion-doped ZBLAN fiber laser passively Q-switched by a Fe:ZnSe crystal is reported. Mid-infrared pulses at 2.78 μm with a repetition rate of 70.4 kHz and a pulse duration of 5.8 μs were generated. © OSA 2012.
• Wei, C., Zhu, X., Norwood, R. A., & Peyghambarian, N. (2012). Er³⁺-doped ZBLAN fiber laser Q-switched by Fe: ZnSe. CLEO: Science and Innovations, CLEO_SI 2012, JW2A.61.
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  Abstract: A highly erbium ion-doped ZBLAN fiber laser passively Q-switched by a Fe:ZnSe crystal is reported. Mid-infrared pulses at 2.78 μm with a repetition rate of 70.4 kHz and a pulse duration of 5.8 μs were generated. © 2012 Optical Society of America.
• Wei, C., Zhu, X., Norwood, R. A., & Peyghambarian, N. (2012). Er³⁺-doped ZBLAN fiber laser Q-switched by Fe:ZnSe. 2012 Conference on Lasers and Electro-Optics, CLEO 2012.
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  Abstract: A highly erbium ion-doped ZBLAN fiber laser passively Q-switched by a Fe:ZnSe crystal is reported. Mid-infrared pulses at 2.78 μm with a repetition rate of 70.4 kHz and a pulse duration of 5.8 μs were generated. © 2012 OSA.
• Wei, C., Zhu, X., Norwood, R. A., & Peyghambarian, N. (2012). Er³⁺-doped ZBLAN fiber laser Q-switched by Fe:ZnSe. Optics InfoBase Conference Papers.
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  Abstract: A highly erbium ion-doped ZBLAN fiber laser passively Q-switched by a Fe:ZnSe crystal is reported. Mid-infrared pulses at 2.78 μm with a repetition rate of 70.4 kHz and a pulse duration of 5.8 μs were generated. © 2012 Optical Society of America.
• Wei, C., Zhu, X., Norwood, R. A., & Peyghambarian, N. (2012). Passively Q-switched 2.8-μm nanosecond fiber laser. IEEE Photonics Technology Letters, 24(19), 1741-1744.
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  Abstract: A diode-pumped erbium ion-doped single-mode ZBLAN fiber laser passively Q-switched by a Fe 2+: ZnSe crystal is reported. Mid-infrared (MIR) pulses at 2.8 μm with a pulse energy of 2.0 μJ and pulse duration of 370 ns, corresponding to a peak power of 5.34 W, are achieved at a repetition rate of 161 kHz. Our experiment demonstrates that Fe 2+: ZnSe crystal is a promising Q-switching element for high power pulsed MIR fiber lasers. © 2012 IEEE.
• Wei, C., Zhu, X., Norwood, R. A., & Peyghambarian, N. (2012). Passively continuous-wave mode-locked Er³⁺-doped ZBLAN fiber laser at 2.8 μm. Optics Letters, 37(18), 3849-3851.
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  PMID: 23041880;Abstract: An Er3+-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber laser was passively mode-locked by inserting a Fe2+:ZnSe crystal into the free space part of the cavity. Continuous-wave mode-locked pulses at 2.8 μmwith a pulse duration of 19 ps estimated from the spectral bandwidth and an average power of 51 mW were generated when a collimated beam traversed the Fe 2+:ZnSe crystal, while Q-switched mode-locked pulses were obtained when the Fe2+:ZnSe crystal was illuminated by the focused beam. © 2012 Optical Society of America.
• Zhou, R., Shi, W., Petersen, E., Chavez-Pirson, A., Stephen, M., & Peyghambarian, N. (2012). Transform-limited, injection seeded, Q-switched, ring cavity fiber laser. Journal of Lightwave Technology, 30(16), 2589-2595.
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  Abstract: We report an Er-doped, actively Q-switched, fiber laser, generating transform-limited pulses based on single-frequency fiber laser seeded ring cavity. The output pulsewidth can be tuned from hundreds of nanoseconds to several microseconds by changing the repetition rate or the open time of the electrical pulse trigger. This injection-seeded, Q-switched ring cavity fiber laser can be operated over the whole C-band. In addition, a theoretical model is developed to numerically study the pulse characteristics by changing the acousto-optic modulator transmission as well as several cavity parameters, such as the cavity length and loss. The numerical results are in good agreement with the experimental results. © 2012 IEEE.
• Zhu, X., Shi, W., Zong, J., Nguyen, D., Norwood, R. A., Chavez-Pirson, A., & Peyghambarian, N. (2012). 976 nm single-frequency distributed Bragg reflector fiber laser. Optics Letters, 37(20), 4167-4169.
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  PMID: 23073399;Abstract: A single-frequency distributed Bragg reflector (DBR) fiber laser at 976 nm was developed with a 2 cm long highly ytterbium-doped phosphate fiber and a pair of silica fiber Bragg gratings. More than 100 mW of linearly polarized output was achieved from the all-fiber DBR laser with a linewidth less than 3 kHz. The outstanding features of this single-frequency laser also include ultralow relative intensity noise and high wavelength stability. This fiber laser is an excellent seeder for high-power 976 nm narrow-linewidth laser amplifiers that can be used for efficient coherent blue-light generation through frequency doubling. © 2012 Optical Society of America.
• Zhu, X., Wang, J., Nguyen, D., Thomas, J., Norwood, R. A., & Peyghambarian, N. (2012). Linear and nonlinear optical properties of Co₃O₄ nanoparticle-doped polyvinyl-alcohol thin films. Optical Materials Express, 2(1), 103-110.
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  Abstract: Thin films made from a composite of the polymer polyvinylalcohol and cobalt oxide (Co3O4) nanoparticles were fabricated by spin coating. Linear and nonlinear optical properties of thin films with thicknesses of hundreds of nanometers were investigated. The refractive index and absorption coefficient were measured and two direct band gaps (Eg = 1.38 eV and 2.0 eV) were determined from the absorption spectrum. Reversed saturable absorption and saturable absorption were observed when the films were illuminated with the different fluences. Optical nonlinearities corresponding to reverse saturable absorption were measured by the z-scan technique. A nonlinear refractive index (n2) of ~10-10 cm2/W and nonlinear absorption (β) of ~103 cm/GW have been measured from 425 nm to 675 nm. The experimental results show that the Co3O4 nanoparticle/PVA composite is a promising material for nonlinear optical devices in the visible, since it takes advantages of the high optical nonlinearities of transition metal oxides and the superior mechanical properties and convenient fabrication properties of polymers. © 2011 Optical Society of America.
• Zhu, X., Zong, J., Miller, A., Wiersma, K., Norwood, R. A., Prasad, N. S., Chavez-Pirson, A., & Peyghambarian, N. (2012). Single-frequency Ho³⁺-doped ZBLAN fiber laser at 1200 nm. Optics Letters, 37(20), 4185-4187.
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  PMID: 23073405;Abstract: A single-frequency (SF) fiber laser at 1200 nm was developed with a distributed Bragg reflector (DBR) configuration by splicing a 22 mm long highly holmium-doped ZBLAN (ZrF4-BaF2-LaF3-AlF 3-NaF) fiber with a pair of silica fiber Bragg gratings. The linewidth was estimated to be less than 100 kHz based on the measured frequency noise. The relative intensity noise was measured to be 19 dB. Our results highlight the exciting prospect that wavelength coverage of SF DBR fiber lasers can be expanded significantly by using rare-earth-doped ZBLAN fibers. © 2012 Optical Society of America.
• Zhu, X., Zong, J., Norwood, R. A., Chavez-Person, A., Peyghambarian, N., & Prasad, N. (2012). Holmium-doped ZBLAN fiber lasers at 1.2 μm. Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 8237.
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  Abstract: Holmium (Ho 3+)-doped ZBLAN glasses have been investigated for the purpose of achieving efficient fiber lasers at 1.2 μm. Because of the long lifetime of the upper laser level and the small phonon energy in Ho 3+-doped ZBLAN glasses, strong fluorescence at 1.2 μm that usually cannot be observed in Ho-doped silica glass has been measured. Fluorescence of 1 mol%, 3 mol%, and 6 mol% Ho 3+-doped ZBLAN glasses are reported. The effect of cerium and terbium ions on the emission of Ho 3+-doped ZBLAN glass has also been studied. Obstacles to achieving an efficient Ho 3+-doped ZBLAN laser are analyzed and discussed. In studies of a commercial Ho 3+-doped ZBLAN fiber laser, it was found that the 3 μm four-energy-level laser can easily overwhelm the 1.2 μm laser, which is a three-energy-level system having the same upper laser level with the 3 μm laser. In order to effectively suppress the competiting 3 μm transition, advanced Ho 3+-doped ZBLAN fiber has been designed and fabricated for 1.2 μm fiber lasers. Fiber lasers at 1.2 μm using the new Ho 3+-doped ZBLAN fiber have been developed. Our experiments demonstrate that the new Ho 3+-doped ZBLAN fiber is an efficient gain medium for lasers at 1.2 μm. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
• Demir, V., Araci, I. E., Kropachev, A., Skotheim, T., Norwood, R. A., & Peyghambarian, N. (2011). Nanoamorphous carbon as a blackbody source in plasmonic thermal emitters. Applied Optics, 50(2), 218-221.
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  PMID: 21221147;Abstract: Ag/dielectric/Ag-type plasmonic thermal emitters (PTEs) following a hexagonal lattice were fabricated, and their plasmonic emission spectrums were characterized with Fourier transform infrared spectroscopy. Nanoamorphous carbon (NAC) is used as a dielectric layer. Doping NAC with various materials over a wide range of levels enables control of the resistivity of the composite films where MoSi2 was selected as the dopant. Wavelength tuning in the range of 4-7 μm is demonstrated by changing the conductivity of the composite films as well as the lattice periodicity of the hexagonal lattice. We also tested the mechanical stability of the PTEs under mechanical strains. © 2011 Optical Society of America.
• Haji-Saeed, B., Khoury, J., Woods, C. L., Kierstead, J., Peyghambarian, N., & Yamamoto, M. (2011). Optical correlation via dynamic range compression using organic photorefractive materials. Proceedings of SPIE - The International Society for Optical Engineering, 8055.
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  Abstract: In this paper, we demonstrate optical correlation via dynamic range compression in two-beam coupling using thin-film organic materials. In contrast to the first demonstration, in which it was not possible to demonstrate correlation with complicated input, here we demonstrate correlation with extremely challenging cases involving finger prints, images in clutter, and SAR images. Our correlation results outperform many correlation results, including ones based on optimal filters. © 2011 SPIE.
• Han, L., Chen, S., Schülzgenx, A., Zeng, Y., Song, F., Tian, J., & Peyghambarian, N. (2011). Calculation and optimization of electromagnetic resonances and local intensity enhancements for plasmon metamaterials with sub-wavelength double-slots. Progress in Electromagnetics Research, 113, 161-177.
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  Abstract: We propose two metamaterials with sub-wavelength double-slots ⌋ single-side double-slot metamaterial and double-side double-slot metamaterial. The dependence of the electromagnetic resonances and local intensity enhancements on the structural parameters is studied by thefnite-difference time-domain technique and thefnite element method. Results show that the central-arm of a double-slot structure strongly influences frequency and local intensities at both highand low-frequency resonances. Very strongfeld localization can be achieved at the high-frequency resonance and its particular distribution can be well controlled by the width of the central-arm. A double-side double-slot structure can be utilized to separately enhance the high-frequency resonance, while suppressing the low-frequency resonance. The simulation results are discussed in terms of plasmon resonances.
• Hofmann, P., Pirson-Chavez, A., Schülzgen, A., Xiong, L., Laronche, A., Albert, J., & Peyghambarian, N. (2011). Low noise single frequency all-phosphate fiber laser. Proceedings of SPIE - The International Society for Optical Engineering, 8039.
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  Abstract: The noise power spectrum of solid-state lasers - including fiber lasers - exhibits a characteristic peak at the relaxation oscillation frequency. The tails associated with this peak extend to neighboring spectral ranges and may increase the noise level above acceptable limits in applications using weak signals. One of the key factors to reduce the relative intensity noise (RIN) amplitude is a low loss laser resonator. We describe a method to ultimately reduce the intensity noise in single frequency phosphate fiber lasers by minimizing intra-cavity losses caused by fusion splices between fibers made of different materials. Conventional fiber Bragg gratings written in silica fibers have been replaced with gratings written in phosphate glass fibers. The quality of the intra-cavity fusion splice has been improved due to material similarity. All-phosphate fiber laser devices have been built and tested utilizing the new gratings. The results show relative intensity noise amplitudes that are very similar to those of conventionally fabricated devices. Challenges in the grating writing process are currently preventing the new devices from surpassing their commercial counterparts in terms of performance. However, this type of all phosphate glass fiber lasers may ultimately lead to a new generation of commercial single frequency fiber lasers with improved intensity noise performance. © 2011 SPIE.
• Khoury, J., Haji-Saeed, B., Woods, C. L., Kierstead, J., Peyghambarian, N., & Yamamoto, M. (2011). Four-wave mixing real-time intensity filtering with organic photorefractive materials. Optical Engineering, 50(1).
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  Abstract: In this paper, we exploit the nonlinearity inherent in four-wave mixing in organic photorefractive materials and demonstrate edge enhancement, contrast conversion, and defect enhancement in a periodic structure. With the availability of these materials, which have large space-bandwidth products, edge enhancement, contrast conversion and defect enhancement are possible. Some simulation results also are provided. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
• Khoury, J., Haji-Saeed, B., Woods, C. L., Kierstead, J., Peyghambarian, N., & Yamamoto, M. (2011). Optical dynamic range compression deconvolution and correlation using organic photorefractive materials. Proceedings of SPIE - The International Society for Optical Engineering, 8055.
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  Abstract: Imaging in atmospheric turbulence and target recognition in cluttered environments have been research topics for many years. Currently, there are some well-established techniques for image restoration and recognition; however, if the atmospheric turbulence becomes a severe scattering medium and the surrounding environment is very cluttered, most conventional methods, such as inverse filtering and Wiener filtering, will be inadequate for correcting and recognizing the captured images. In this paper, we experimentally demonstrate nonlinear dynamic range compression techniques for image restoration and correlation via two-beam coupling and four wave mixing in organic photorefractive films. © 2011 SPIE.
• Nagel, J. A., Temyanko, V., Dobler, J., Dianov, E. M., Biriukov, A. S., Sysoliatin, A. A., Norwood, R. A., & Peyghambarian, N. (2011). High-power narrow-linewidth continuous-wave Raman amplifier at 1.27 μm. IEEE Photonics Technology Letters, 23(9), 585-587.
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  Abstract: A high-power narrow-linewidth continuous-wave (CW) Raman fiber amplifier at 1.27 μm is demonstrated for remote sensing measurements of atmospheric oxygen O2. The amplifier uses phosphosilicate fiber in both a standard single-mode design and with the core size varying in the longitudinal direction for stimulated Brillouin scattering (SBS) suppression. The highest reported power level at this wavelength to date, a total peak power of 3 W, has been achieved for online (2.4 W) and offline (580 mW) spectroscopic measurements, in agreement with theoretical predictions. Additionally, it is shown that when 60-kHz sinusoidal amplitude modulation is applied to the amplifier seed signal, the modulated wave form is preserved at the amplifier output with 1.8 W total average power being obtained. © 2006 IEEE.
• Nagel, J. A., Temyanko, V., Norwood, R. A., Peyghambarian, N., Dobler, J. T., Dianov, E. M., Biriukov, A. S., & Sysoliatin, A. A. (2011). Narrow linewidth continuous wave fiber raman amplifier for remote sensing of atmospheric O₂ at 1.27μm. Optics InfoBase Conference Papers.
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  Abstract: We report on the development of a continuous wave narrow linewidth fiber Raman amplifier for remote sensing of atmospheric oxygen at 1.27μm with a total combined peak power of 3W for online and offline channels. © 2010 Optical Society of America.
• Petersen, E. B., Shi, W., Chavez-Pirson, A., & Peyghambarian, N. (2011). Efficient parametric cavity enhanced terahertz generation based on quasi-phase matched GaP bonded structures. 2011 Conference on Lasers and Electro-Optics: Laser Science to Photonic Applications, CLEO 2011.
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  Abstract: We demonstrate cavity enhanced parametric THz generation with power of 339μW and enhancement factor of ∼151 through quasi-phase-matched GaP pumped by 1.5um pulsed fiber lasers. © 2011 OSA.
• Petersen, E. B., Shi, W., Chavez-Pirson, A., & Peyghambarian, N. (2011). Efficient parametric cavity enhanced terahertz generation based on quasi-phase matched GaP bonded structures. Optics InfoBase Conference Papers.
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  Abstract: We demonstrate cavity enhanced parametric THz generation with power of 339μW and enhancement factor of ~151 through quasi-phase-matched GaP pumped by 1.5um pulsed fiber lasers. © OSA/ CLEO 2011.
• Petersen, E. B., Shi, W., Chavez-Pirson, A., Peyghambarian, N., & Cooney, A. T. (2011). Efficient parametric terahertz generation in quasi-phase-matched GaP through cavity enhanced difference-frequency generation. Applied Physics Letters, 98(12).
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  Abstract: We report an efficient parametric terahertz (THz) source by using bonded quasi-phase-matched (QPM) GaP crystals pumped by the C-band pulsed fiber lasers in a master oscillator power amplifier configuration, based on difference frequency generation (DFG). We observed that the QPM-GaP crystals can effectively increase the THz generation power and efficiency by increasing the number of periods. Moreover, we observed external cavity enhanced THz DFG by placing the QPM-GaP crystal in an external ring cavity. The THz cavity enhancement factor of approximately 250 has been achieved in comparison with a single-pass THz DFG. The maximum THz average power can reach 339 μW, corresponding to a power conversion efficiency of 2.43× 10-4 and a quantum efficiency of 3.16%. © 2011 American Institute of Physics.
• Peyghambarian, N., Christenson, C. W., Greenlee, C., Lynn, B., Thomas, J., Blanche, P., Voorakaranam, R., Hilaire, P. S., LaComb, L. J., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. N. (2011). Interdigitated coplanar electrodes for enhanced sensitivity in a photorefractive polymer. Optics letters, 36(17).
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  Organic photorefractive polymer composites can be made to exhibit near 100% diffraction efficiency and fast writing times, though large external slants are needed to project the applied field onto the grating vector. We show here that the use of interdigitated electrodes on a single plane provides similar performance to these standard devices and geometries but without a external slant angle. This new device's structure also greatly improves the diffraction efficiency and sensitivity compared to less slanted standard devices necessary for some real applications, such as holographic displays, optical coherence imaging, and in-plane switching.
• Peyghambarian, N., Demir, V., Araci, I. E., Kropachev, A., Skotheim, T., Norwood, R. A., & Peyghambarian, N. N. (2011). Nanoamorphous carbon as a blackbody source in plasmonic thermal emitters. Applied optics, 50(2).
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  Ag/dielectric/Ag-type plasmonic thermal emitters (PTEs) following a hexagonal lattice were fabricated, and their plasmonic emission spectrums were characterized with Fourier transform infrared spectroscopy. Nanoamorphous carbon (NAC) is used as a dielectric layer. Doping NAC with various materials over a wide range of levels enables control of the resistivity of the composite films where MoSi(2) was selected as the dopant. Wavelength tuning in the range of 4-7 μm is demonstrated by changing the conductivity of the composite films as well as the lattice periodicity of the hexagonal lattice. We also tested the mechanical stability of the PTEs under mechanical strains.
• Peyghambarian, N., Greenlee, C., Luo, J., Leedy, K., Bayraktaroglu, B., Norwood, R. A., Fallahi, M., Jen, A. K., & Peyghambarian, N. N. (2011). Electro-optic polymer spatial light modulator based on a Fabry-Perot interferometer configuration. Optics express, 19(13).
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  A spatial light modulator (SLM) based on a Fabry-Perot interferometer configuration has been fabricated and tested. The Fabry-Perot spacer layer is a thin film of the SEO100 electro-optic polymer which serves as the nonlinear medium. Measurement results demonstrate the modulation of multiple pixels operating simultaneously at frequencies ranging from 300 kHz to 800 kHz which is significantly faster than SLMs based on liquid crystal and digital micromirror device technology. An average modulation contrast of 50% for all pixels is achieved with a drive voltage of 70 V(rms) at 100 kHz. Microwave speeds and CMOS compatibility are feasible with improved transmission line and cavity design.
• Peyghambarian, N., Kieu, K. Q., Klein, J., Evans, A., Barton, J. K., & Peyghambarian, N. N. (2011). Ultrahigh resolution all-reflective optical coherence tomography system with a compact fiber-based supercontinuum source. Journal of biomedical optics, 16(10).
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  We report the construction and characterization of an all-reflective optical coherence tomography (OCT) system using a newly developed compact fiber-based broadband supercontinuum source. The use of only reflective optical components has enabled us to avoid chromatic dispersion effects and to obtain ultrahigh resolution OCT images of biological samples. We achieved an axial resolution of 2 μm in air with 87 dB dynamic range at a center wavelength around 1300 nm.
• Peyghambarian, N., Kieu, K., Schneebeli, L., Hales, J. M., Perry, J. W., Norwood, R. A., & Peyghambarian, N. N. (2011). Demonstration of Zeno switching through inverse Raman scattering in an optical fiber. Optics express, 19(13).
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  We report the observation of Zeno switching through an inverse Raman scattering (IRS) process in an optical fiber. In IRS, light at the anti-Stokes frequency is strongly attenuated in the presence of a pump field, allowing it to be used for all-optical switching and modulation. Our observed level of induced absorption via IRS in the optical fiber is > 20 dB in a time scale of less than 5 ps. The full Raman response spectrum was extracted experimentally and excellent agreement was found between the experimental data and theoretical modeling of IRS.
• Peyghambarian, N., Valley, P., Savidis, N., Schwiegerling, J., Dodge, M. R., Peyman, G., & Peyghambarian, N. N. (2011). Adjustable hybrid diffractive/refractive achromatic lens. Optics express, 19(8).
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  We demonstrate a variable focal length achromatic lens that consists of a flat liquid crystal diffractive lens and a pressure-controlled fluidic refractive lens. The diffractive lens is composed of a flat binary Fresnel zone structure and a thin liquid crystal layer, producing high efficiency and millisecond switching times while applying a low ac voltage input. The focusing power of the diffractive lens is adjusted by electrically modifying the sub-zones and re-establishing phase wrapping points. The refractive lens includes a fluid chamber with a flat glass surface and an opposing elastic polydimethylsiloxane (PDMS) membrane surface. Inserting fluid volume through a pump system into the clear aperture region alters the membrane curvature and adjusts the refractive lens' focal position. Primary chromatic aberration is remarkably reduced through the coupling of the fluidic and diffractive lenses at selected focal lengths. Potential applications include miniature color imaging systems, medical and ophthalmic devices, or any design that utilizes variable focal length achromats.
• Peyghambarian, N., Zhu, X., Schülzgen, A., Wei, H., Kieu, K., & Peyghambarian, N. N. (2011). White light Bessel-like beams generated by miniature all-fiber device. Optics express, 19(12).
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  Micron-sized white light propagation invariant beams generated by a simple and compact fiber device are presented. The all-fiber device is fabricated by splicing a short piece of large-core multimode fiber onto a small-core single mode white light delivery fiber. Because this fiber device offers an inherent spatial coherence, nondiffracting white light beams can be created with a temporally incoherent broadband light source (a halogen bulb) and, most importantly, the surrounding fringes don't fade as the bandwidth of the light source increases because the underlying physics of this fiber device is different from that of the axicon. White light Bessel-like beams have been generated from multimode fibers with core diameters of 50 μm, 105 μm, and 200 μm. The distance of nondiffracting propagation of the white light Bessel beam increases with increasing core size of the multimode fiber. Propagation characteristics of red, green, and blue individual beams are also presented.
• Schülzgen, A., Hofmann, P., Li, L., Peyghambarian, N., Xiong, L., Laronche, A., & Albert, J. (2011). Distributed feedback lasers in phosphate glass active fiber. Optics InfoBase Conference Papers.
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  Abstract: Writing grating structures directly into the highly-doped core of phosphate glass fibers enables the fabrication of distributed feedback lasers. Efficient pump absorption allows for novel cladding pumped distributed feedback fiber lasers. © 2010 Optical Society of America.
• Sheng, C., Chen, Q., Norwood, R. A., Wang, J., Thomas, J., & Peyghambarian, N. (2011). Simple way for achieving passive all-optical switching of continuous waves lasers using pure nematic liquid crystal. Applied Optics, 50(30), 5788-5790.
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  PMID: 22015405;Abstract: We have examined pure nematic liquid crystal (LC), 4′-pentyl-4- biphenylcarbonitrile (5-CB), with a 90° twisted alignment within a cell made of two cross-polarized absorptive plastic polarizers, and investigated the nonlinear transmission properties using cw (532 nm) lasers.We observed optically self-activated polarization switching with a factor of three lower switching power than a dye-doped LC cell with similar linear transmittance using glass substrates.We also studied the dynamics of the switching processes and observed millisecond switching time.These studies have demonstrated a simpler but more efficient way for fabricating broadband, low switching power, millisecond time scale switching, and optical limiting devices.© 2011 Optical society ofamerica.
• Shi, W., Moor, N., Petersen, E. B., Nguyen, D. T., Yao, Z., Stephen, M. A., Chavez-Pirson, A., & Peyghambarian, N. (2011). High energy pulsed fiber laser transmitters in the C and L band for coherent lidar applications. Proceedings of SPIE - The International Society for Optical Engineering, 8286.
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  Abstract: We report a monolithic specialized high stimulated Brillouin scattering (SBS) threshold fiber laser/amplifier in the C and L band based on highly co-doped phosphate glass fibers. This represents an important new development for coherent LIDAR and remote sensing applications. By using single mode polarization-maintaining large core highly Er/Yb codoped phosphate fibers in the power amplifier stages, we have achieved the highest peak power of 2.02 kW at 1530 nm for 105 ns pulses with transform-limited linewidth, and with a corresponding pulse energy of about 0.212 mJ. The achieved high-energy pulses were frequency doubled by using a commercial periodically poled lithium niobate (PPLN) crystal, and the highest SHG peak power of 271 W has been achieved for the SHG pulses at 765 nm that can be used for oxygen coherent remote sensing. In the L band, more than 80 μJ fiber laser pulses at 1572 nm with 1-2 μs pulse width and transform-limited linewidth have been achieved by using a monolithic fiber laser system in MOPA configuration, which can be used for CO2 coherent remote sensing. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
• Shi, W., Petersen, E. B., Chavez-Pirson, A., & Peyghambarian, N. (2011). Coherent monolithic THz generation based on quasi-phase-matched GaP bonded structures pumped by pulsed fiber lasers at ∼ 1.5 μm. Proceedings of SPIE - The International Society for Optical Engineering, 7917.
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  Abstract: We report coherent monolithic THz generation in GaP QPM bonded structures based on difference-frequency generation (DFG) using two pulsed fiber lasers in the C-band. We observed that the QPM-GaP crystals effectively increase the THz generation power and efficiency with increasing periods of QPM structures. The azimuthal dependence of the THz generation for the GaP QPM bonded structure has been measured when the polarization directions of the two pump beams are orthogonal and parallel, respectively. Moreover, we observed the external cavity enhanced THz DFG when we put the QPM-GaP crystal in an external ring cavity, for the first time. The THz cavity enhancement factor of ∼250 has been achieved compared with the single-pass THz DFG. The maximum THz average power can reach 339 μW, corresponding to a power conversion efficiency of 2.43×10-4 and quantum efficiency of 3.16%. © 2011 SPIE.
• Shi, W., Petersen, E. B., Moor, N., Chavez-Pirson, A., & Peyghambarian, N. (2011). Single frequency actively Q-switched 2 μm fiber laser by using highly Tm-doped germanate fiber. 2011 Conference on Lasers and Electro-Optics: Laser Science to Photonic Applications, CLEO 2011.
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  Abstract: We report a unique all-fiber single-frequency actively Q-switched laser operating at 1920 nm by using a piezo to press the fiber in the fiber Bragg grating cavity and modulate the fiber birefringence, enabling Q-switching. © 2011 OSA.
• Shi, W., Petersen, E. B., Moor, N., Chavez-Pirson, A., & Peyghambarian, N. (2011). Single frequency actively Q-switched 2 μm fiber laser by using highly Tm-doped germanate fiber. Optics InfoBase Conference Papers.
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  Abstract: We report a unique all-fiber single-frequency actively Q-switched laser operating at ~1920 nm by using a piezo to press the fiber in the fiber Bragg grating cavity and modulate the fiber birefringence, enabling Q-switching. ©2010 Optical Society of America.
• Shi, W., Petersen, E. B., Nguyen, D. T., Yao, Z., Chavez-Pirson, A., Peyghambarian, N., & Jirong, Y. u. (2011). 220 μj monolithic single-frequency Q-switched fiber laser at 2 μm by using highly tm-doped germanate fibers. Optics Letters, 36(18), 3575-3577.
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  PMID: 21931395;Abstract: We report a unique all fiber-based single-frequency Q-switched laser in a monolithic master oscillator power amplifier configuration at ∼1920nm by using highly Tm-doped germanate fibers for the first time. The actively Q-switched fiber laser seed was achieved by using a piezo to press the fiber in the fiber Bragg grating cavity and modulate the fiber birefringence, enabling Q-switching with pulse width and repetition rate tunability. A single-mode polarization maintaining large core 25 μm highly Tm-doped germanate fiber was used in the power amplifier stage. For 80 ns pulses with 20 kHz repetition rate, we achieved 220 μJ pulse energy, which corresponds to a peak power of 2:75kW with transform-limited linewidth. © 2011 Optical Society of America.
• Shi, W., Petersen, E., Moor, N., Chavez-Pirson, A., & Peyghambarian, N. (2011). All fiber-based single-frequency Q-switched laser pulses at 2 μm for LIDAR and remote sensing applications. Proceedings of SPIE - The International Society for Optical Engineering, 8164.
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  Abstract: We report an all fiber-based single-frequency Q-switched 2 μm pulsed laser based on highly Tm-doped germanate fiber by using a piezo to induce stress in fiber laser cavity. The pulse width of this Q-switched fiber laser can be tuned from 10's ns to sub-μs. The repetition rate can be tuned from 100 Hz to 100's kHz. The average power is ∼ mW-level, peak power wattlevel, and pulse energy 30-75 nJ without any amplifier. Moreover, this transform-limited fiber laser pulses has been scaled up to 220 μJ by using a newly developed SM PM highly Tm-doped germanate fiber 25/250μm for transform-limited 80 ns pulses at repetition rate 20 kHz. This narrow linewidth high energy MOPA-based pulsed fiber laser can be used for LIDAR and laser remote sensing. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
• Taher, M., Gebavi, H., Taccheo, S., Jousteau, L., Milanese, D., & Peyghambarian, N. (2011). Lifetime and cross-relaxation in highly Tm-doped glasses for 2 micron lasers. Proceedings of SPIE - The International Society for Optical Engineering, 7934.
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  Abstract: In this paper, we present our recent investigation of highly doped Tm 3+ tellurite glass. The optical properties of series of tellurite glass samples (75 mol % TeO2 - 20 mol ZnO - 5 mol % Na2O) highly doped with Tm3+ ions were reported and discussed. An exhaustive set of samples from low concentration to very high have been used in this study. Cross relaxation process has been studied and cross-relaxation parameter has been calculated. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
• Thomas, J., Christenson, C. W., Blanche, P., Yamamoto, M., Norwood, R. A., & Peyghambarian, N. (2011). Photoconducting polymers for photorefractive 3D display applications. Chemistry of Materials, 23(3), 416-429.
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  Abstract: Photorefractive composites derived from photoconducting polymers offer the advantage of dynamically recording holograms without the need for processing of any kind. Thus, they are the material of choice for many cutting edge applications, such as updatable 3D displays and imaging through a scattering medium. This article reviews the basic properties of photorefractive polymer systems and the inherent advantages that have attracted much attention. The chemistry and physics relevant for the design of the high-performance guest-host composite are discussed and recent advances emphasized. In particular, a charge transporting polymer with high mobility and historyindependent response times is highlighted, as well as polymer systems useful for holographic displays and the material considerations necessary to develop high-speed, large-sensitivity composites. © 2010 American Chemical Society.
• Thomas, J., Christenson, C. W., Lynn, B., Blanche, P. -., Voorakaranam, R., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. (2011). Recent advances in photorefractive polymers. Proceedings of SPIE - The International Society for Optical Engineering, 8113.
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  Abstract: Photorefractive composites derived from conducting polymers offer the advantage of dynamically recording holograms without the need for processing of any kind. Thus, they are the material of choice for many cutting edge applications, such as updatable three-dimensional (3D) displays and 3D telepresence. Using photorefractive polymers, 3D images or holograms can be seen with the unassisted eye and are very similar to how humans see the actual environment surrounding them. Absence of a large-area and dynamically updatable holographic recording medium has prevented realization of the concept. The development of a novel nonlinear optical chromophore doped photoconductive polymer composite as the recording medium for a refreshable holographic display is discussed. Further improvements in the polymer composites could bring applications in telemedicine, advertising, updatable 3D maps and entertainment. © 2011 SPIE.
• Thomas, J., Gangopadhyay, P., Araci, E., Norwood, R. A., & Peyghambarian, N. (2011). Nanoimprinting by melt processing: An easy technique to fabricate versatile nanostructures. Advanced Materials, 23(41), 4782-4787.
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  PMID: 21928300;Abstract: Insights gained from rheological and contact angle measurements of plasticized and non-plasticized polymers have led to the development of a simple method to print densely packed micro- and nanoscale features without proximity effects. Versatile large-area nanopatterns and landscapes with a high degree of fidelity are successfully imprinted. This technique promises a variety of polymer nanostructures to a wide spectrum of scientific fields. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
• Tian, M., Ping, L. u., Schülzgen, A., Peyghambarian, N., & Liu, D. (2011). Double-resonance plasmon and polarization effects in a SERS fiber sensor with a grid nanostructure. Optics Communications, 284(7), 2061-2064.
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  Abstract: We presented a systematic study of surface enhanced Raman scattering (SERS) fiber sensor with a grid nanostructure. The plasmonic resonance peak is stable when measuring gas and double-resonance plasmon can be effectively excited; meanwhile local electric field can be strongly enhanced with the metal coated nanostructured fiber facet. Studies on the influence of polarization effects, the plasmon resonance wavelength shift is relatively small in our structure. © 2011 Elsevier B.V.
• Xiong, L., Hofmann, P., Schulzgen, A., Peyghambarian, N., & Albert, J. (2011). A short dual-wavelength DBR phosphate fiber laser. 2011 Conference on Lasers and Electro-Optics: Laser Science to Photonic Applications, CLEO 2011.
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  Abstract: A 5cm-long monolithic distributed Bragg reflector fiber laser is fabricated by directly writing Bragg gratings on Er/Yb co-doped phosphate fiber. Stable narrow-linewidth dual-wavelength emission with 38 pm wavelength spacing is achieved. © 2011 OSA.
• Xiong, L., Hofmann, P., Schülzgen, A., Peyghambarian, N., & Albert, J. (2011). A short dual-wavelength DBR phosphate fiber laser. Optics InfoBase Conference Papers.
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  Abstract: A 5cm-long monolithic distributed Bragg reflector fiber laser is fabricated by directly writing Bragg gratings on Er/Yb co-doped phosphate fiber. Stable narrow-linewidth dualwavelength emission with 38 pm wavelength spacing is achieved. © OSA/CLEO 2011.
• Araci, I. E., Demir, V., Kropachev, A., Skotheim, T., Norwood, R. A., & Peyghambarian, N. (2010). Mechanical and thermal stability of plasmonic emitters on flexible polyimide substrates. Applied Physics Letters, 97(4).
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  Abstract: We have fabricated Ag/SiO2/Ag plasmonic thermal infrared (IR) emitters with different hexagonal lattice periods on flexible polyimide (PI) membranes. The high temperature resistance and comparable coefficient of thermal expansion with metallic films enabled the fabrication of plasmonic IR emitters on PI films. We have investigated the effects of temperature and mechanical strain on the spectral and structural properties of the flexible emitter. The low heat conductivity and low thermal mass of thin free standing PI substrates enables IR emitters with low power consumption (
• Araci, I. E., Himmelhuber, R., DeRose, C. T., Luo, J. D., Jen, A. K., Norwood, R. A., & Peyghambarian, N. (2010). Alignment-free fabrication of a hybrid electro-optic polymer/ion-exchange glass coplanar modulator. Optics Express, 18(20), 21038-21046.
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  PMID: 20940999;Abstract: A hybrid electro-optic (EO) polymer phase modulator with a 6 μm coplanar electrode gap was realized on ion exchange glass substrates. The critical alignment steps which may be required for hybrid optoelectronic devices were eliminated with a simple alignment-free fabrication technique. The low loss adiabatic transition from glass to EO polymer waveguide was enabled by gray scale patterning of novel EO polymer, AJLY. Total insertion loss of 5 dB and electrode gap of 8 μm was obtained for an optimized device design. EO polymer poling at 135 °C and 75 V/μm was demonstrated for the first time on a phosphate glass substrate and was enabled by the sol-gel buffer layer. © 2010 Optical Society of America.
• Araci, I. E., Norwood, R. A., Luo, J. D., Jen, A. K., & Peyghambarian, N. (2010). Alignment-free fabrication of a hybrid electro-optic polymer modulator platform. Optics InfoBase Conference Papers.
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  Abstract: A hybrid platform for electro-optic (EO) polymer modulators was realized on glass substrates with a simplified fabrication technique. The coplanar configuration device has 4.5 dB insertion loss with 7.5 μm electrode spacing. © OSA/IPR/PS 2010.
• Blanche, P. -., Bablumian, A., Voorakaranam, R., Christenson, C., Lemieux, D., Thomas, J., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. (2010). Future of photorefractive based holographic 3D display. Proceedings of SPIE - The International Society for Optical Engineering, 7619.
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  Abstract: The very first demonstration of our refreshable holographic display based on photorefractive polymer was published in Nature early 20081. Based on the unique properties of a new organic photorefractive material and the holographic stereography technique, this display addressed a gap between large static holograms printed in permanent media (photopolymers) and small real time holographic systems like the MIT holovideo. Applications range from medical imaging to refreshable maps and advertisement. Here we are presenting several technical solutions for improving the performance parameters of the initial display from an optical point of view. Full color holograms can be generated thanks to angular multiplexing, the recording time can be reduced from minutes to seconds with a pulsed laser, and full parallax hologram can be recorded in a reasonable time thanks to parallel writing. We also discuss the future of such a display and the possibility of video rate. © 2009 Copyright SPIE - The International Society for Optical Engineering.
• Blanche, P. -., Bablumian, A., Voorakaranam, R., Christenson, C., Lin, W., Gu, T., Flores, D., Wang, P., Hsieh, W. -., Kathaperumal, M., Rachwal, B., Siddiqui, O., Thomas, J., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. (2010). Holographic three-dimensional telepresence using large-area photorefractive polymer. Nature, 468(7320), 80-83.
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  PMID: 21048763;Abstract: Holography is a technique that is used to display objects or scenes in three dimensions. Such three-dimensional (3D) images, or holograms, can be seen with the unassisted eye and are very similar to how humans see the actual environment surrounding them. The concept of 3D telepresence, a real-time dynamic hologram depicting a scene occurring in a different location, has attracted considerable public interest since it was depicted in the original Star Wars film in 1977. However, the lack of sufficient computational power to produce realistic computer-generated holograms and the absence of large-area and dynamically updatable holographic recording media have prevented realization of the concept. Here we use a holographic stereographic technique and a photorefractive polymer material as the recording medium to demonstrate a holographic display that can refresh images every two seconds. A 50gHz nanosecond pulsed laser is used to write the holographic pixels. Multicoloured holographic 3D images are produced by using angular multiplexing, and the full parallax display employs spatial multiplexing. 3D telepresence is demonstrated by taking multiple images from one location and transmitting the information via Ethernet to another location where the hologram is printed with the quasi-real-time dynamic 3D display. Further improvements could bring applications in telemedicine, prototyping, advertising, updatable 3D maps and entertainment. © 2010 Macmillan Publishers Limited. All rights reserved.
• Borneman, J. D., Drachev, V. P., Chen, K., Kildishev, A. V., Shalaev, V. M., Yamnitskiy, K., Norwood, R., Peyghambarian, N., Padilha, L. A., Webster, S., Hagan, D. J., & W., E. (2010). Two-photon absorption enhancement with gold nanoantenna array. Optics InfoBase Conference Papers.
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  Abstract: Gold dipole nanoantennas which have strong local electromagnetic fields are used to enhance two-photon absorption. A 30 to 40 times enhancement is observed for BDPAS (4,4'- bis(diphenylamino)stilbene) at 600 nm. © 2009 Optical Society of America.
• Christenson, C. W., Blanche, P. -., Voorakaranam, R., Bablumian, A., Thomas, J., Yamamoto, M., Norwood, R. A., & Peyghambarian, N. (2010). Avenues for expanded applicability in photorefractive based holographic 3D displays. Optics InfoBase Conference Papers.
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  Abstract: The first updatable three-dimensional holographic display based on a photorefractive polymer device, exhibiting a fast response, long persistency, and phase stability is discussed. Material and optical setup changes for new and broader applications are outlined. © 2009 Optical Society of America.
• Christenson, C. W., Blanche, P., Tay, S., Voorakaranam, R., Tao, G. u., Lin, W., Wang, P., Yamamoto, M., Thomas, J., Norwood, R. A., & Peyghambarian, N. (2010). Materials for an updatable holographic 3D display. IEEE/OSA Journal of Display Technology, 6(10), 510-516.
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  Abstract: Holography is a powerful technique for providing high-resolution, realistic three-dimensional (3D) images without the need for special eyewear. A material that takes full advantage of the potential of holography, including updatability, has not existed. Here, the first updatable holographic 3D display based on a photorefractive polymer is summarized. The performance characteristics of these materials are measured, and how they relate to the development of additional display enhancements such as pulsed writing, white light viewing, and large viewing angle, are discussed. © 2010 IEEE.
• Christenson, C. W., Thomas, J., Blanche, P. -., Voorakaranam, R., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. (2010). Grating dynamics in a photorefractive polymer with Alq₃ electron traps. Optics Express, 18(9), 9358-9365.
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  PMID: 20588782;Abstract: The electron transporting molecule tris(8-hydroxyquinoline) aluminum (Alq3) was added in low concentrations to a photorefractive polymer composite to provide trapping sites for electrons. This sample exhibited larger two-beam coupling gain, higher diffraction efficiency at lower voltages, and an increased dielectric breakdown strength compared to a control sample. The dynamics also revealed the presence of a competing grating, and a bipolar charge transport model is shown to fit the data. Overall, Alq3 improves the response time, efficiency, and breakdown voltage without a significant increase in absorption or loss of phase stability. This has applications for reflection displays and pulsed writing, where charge trapping and generation are major factors limiting the usefulness of photorefractive polymers. © 2010 Optical Society of America.
• Christenson, C. W., Thomas, J., Blanche, P., Voorakaranam, R., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. (2010). Complementary grating dynamics in photorefractive polymers with Alq ₃. Proceedings of SPIE - The International Society for Optical Engineering, 7599.
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  Abstract: The electron transporting molecule tris(8-hydroxyquinoline) aluminum (Alq3) was introduced into a photorefractive composite in a low density to study the effects of electron traps on the performance. Compared to a control sample, Alq3 samples exhibited higher dielectric strength, over-modulation at reduced voltage, and increased writing speed. Transient measurements indicated grating revelation via decay of a competing grating. The dynamics are consistent with a bipolar charge transport model. Overall, Alq 3 improves the sensitivity, trapping, and breakdown voltage without significant losses in absorption or phase stability. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Gangopadhyay, P., Lopez-Santiago, A., Voorakaranam, R., Himmelhuber, R., Greenlee, C., Thomas, J., Persoons, A., Norwood, R. A., Verbiest, T., Yamada, H., & Peyghambarian, N. (2010). Magnetite-polymethylmethacrylate core-shell nanocomposites: Applications in all-optical magnetometers. Nonlinear Optics Quantum Optics, 41(1), 87-104.
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  Abstract: Amethod has been developed to prepare magnetite nanoparticles core polymer shell nanocomposite. These core shell nanocomposite particles can be further crosslinked into a passive polymer host that provides processable material with high optical transparency and large Verdet constants.Wavelength dependent and saturation Faraday rotation (FR) measured at room temperature in a polymer containing varying concentrations of crosslinked magnetite core poly(3-methyl)methacrylate (PMMA) shell nanocomposite particles has been explained using a long range magnetic field interaction model. The magnitude of the FR in these composites appears to be strongly dependent on the concentration of the particles, the wavelength of measurement, and the size and shape of the nanoparticles. Comparison of the figure of merit of 2.1° in these core-shell nanocomposites to that of 4.2° for yttrium iron garnet at 980 nm indicates that these nanocomposites may find applications in various magnetic and magnetooptic sensors and devices. Using these observations an all-optical magnetometer has been constructed based on magnetite core polymer shell nanocomposite material. A noise equivalent magnetic field sensitivity of 5 nT/√ Hz was observed using a 1 μT 500 Hz control magnetic field. © 2010 Old City Publishing, Inc.
• Gebavi, H., Taher, M., Lousteau, J., Milanese, D., Taccheo, S., Schulzgen, A., Ferraris, M., & Peyghambarian, N. (2010). Spectroscopy of Yb:Tm doped tellurite glasses for efficient infrared fiber laser. Proceedings of SPIE - The International Society for Optical Engineering, 7598.
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  Abstract: We performed extensive spectroscopy of tellurite glasses doped with high concentration of Tm ions for laser emission at around 2 micron wavelength. The aim of the work is to develop a glass suitable for single-frequency fiber laser. In fact such a kind of laser require the use of short cavity length and therefore high gain per unit length medium. Tellurite glasses allows high-doping concentration and are therefore an excellent candidate. In these paper we review our recent results. In particular we address the optical and thermo-mechanical properties of several tellurite glasses (75mol%Te02.20mol%ZnO. 5mol%Na2O) with Tm3+ doping up to 111,564 ppm. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Haji-Saeed, B., Woods, C. L., Kierstead, J., Peyghambarian, N., Yamamoto, M., & Khoury, J. (2010). Real-time intensity filtering with organic photorefractive materials via four wave mixing. Proceedings of SPIE - The International Society for Optical Engineering, 7696.
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  Abstract: In this paper, we exploit the nonlinearity inherent in four-wave mixing in organic photorefractive materials and demonstrate edge enhancement, contrast conversion, and defect enhancement in a periodic structure. With the availability of these materials, which have large space-bandwidth products, edge enhancement, contrast conversion and defect enhancement are possible. © 2010 SPIE.
• Milanese, D., Gebavi, H., Lousteau, J., Ferraris, M., Schülzgen, A., Li, L. i., Peyghambarian, N., Taccheo, S., & Auzel, F. (2010). Tm³⁺ and Yb³⁺ co-doped tellurite glasses for short cavity optical fiber lasers: Fabrication and optical characterization. Journal of Non-Crystalline Solids, 356(44-49), 2378-2383.
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  Abstract: In this paper Tm-doped tellurite glasses (75TeO2-20ZnO-5 Na 2O, mol%) were studied and sensitization with Yb3+ as co-dopant was carried out in order to assess its influence on the emission properties and improve pump efficiency and wavelength emission range. Emission spectra and lifetime measurements were obtained by pumping either at 785 nm or 980 nm, thus exploiting the Yb-Tm energy transfer mechanism. Doping levels of Yb from below 1 to up 5 mol% were investigated in order to evaluate the effectiveness of energy transfer process and glasses containing an overall content of 9 mol% rare earth ions were proved to be successfully fabricated. All glasses were fully characterized from a material and spectroscopic point of view. Tellurite glasses with 4 and 1 mol% of Tm3+ and Yb3+ ions respectively were found to show a good compromise between emission efficiency and lifetime decay values. A quenching concentration of Yb 3+ ions up to 14 mol% was also defined for this type of glass system. © 2010 Elsevier B.V. All rights reserved.
• Nguyen, D. T., Norwood, R. A., & Peyghambarian, N. (2010). Multiple photonic band gaps in 1D fibonacci systems. Optics InfoBase Conference Papers.
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  Abstract: A new multilayer system based on a one-dimensional (1D) Fibonacci sequence that can generate multiple photonic band gaps (MPBG) is presented. The structures are straightforward to make. Its potential for various applications is also discussed. © 2010 Optical Society of America.
• Nguyen, D. T., Norwood, R. A., & Peyghambarian, N. (2010). Multiple spectral window mirrors based on Fibonacci chains of dielectric layers and applications. Proceedings of SPIE - The International Society for Optical Engineering, 7781.
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  Abstract: The unique properties of one-dimensional (1D) Fibonacci chains of dielectric layers are experimentally demonstrated and exploited for the design of new mirrors with multiple reflection spectral windows. The new mirror structures are simple, straightforward to make and enable a wide variety of multiple spectral window device performance to be achieved. By changing the thickness of the layers or the order of the Fibonacci chain, tens or even hundreds of windows can be obtained with the same approximate reflectivity over a very broad spectral region. These mirrors have numerous applications in photonics and optoelectronics. © 2010 SPIE.
• Nguyen, D. T., Norwood, R. A., & Peyghambarian, N. (2010). Multiple spectral window mirrors based on Fibonacci chains of dielectric layers. Optics Communications, 283(21), 4199-4202.
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  Abstract: The unique properties of one-dimensional (1D) Fibonacci chains of dielectric layers are experimentally demonstrated and exploited for the design of new mirrors with multiple reflection spectral windows. The new mirror structures are simple, straightforward to make and enable a wide variety of multiple spectral window device performance to be achieved. By changing the thickness of the layers or the order of the Fibonacci chain, tens or even hundreds of windows can be obtained with the same approximate reflectivity over a very broad spectral region. These mirrors have numerous applications in photonics and optoelectronics. © 2010 Elsevier B.V. All rights reserved.
• Norwood, R. A., Thomasa, J., Peyghambarian, N., Wang, J., Li, L., Ouchen, F., & Grote, J. E. (2010). Hybrid DNA materials for energy storage. Proceedings of SPIE - The International Society for Optical Engineering, 7765.
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  Abstract: We investigate the dielectric and electrical properties of sol-gel/DNA-CTMA blends, with particular interest in capacitor applications in energy storage. Methacryloyloxypropyltrimethoxysilane (MAPTMS) was the solgel precursor, and DNA-CTMA was blended in to the resulting sol-gel at various weight percentages. The blends were tested for their dielectric properties and dielectric breakdown strength; the 5% DNA blend was found to be optimal with a dielectric constant in the range of 7.5, while the breakdown strength was greater than 800 V/μm for 1 μm films and about 500 V/μm for 5μm films. Hybrid sol-gel/DNA-CTMA/barium titanate nanoparticle composites were also formulated and their dielectric properties measured. While a high dielectric constant was achieved (38), this came at the expense of a significantly reduced breakdown voltage (160V/μm). We discuss these results as well as other aspects of the dielectric and electrical properties of these blends. © 2010 SPIE.
• Petersen, E. B., Shi, W., Nguyen, D. T., Yao, Z., Zong, J., Chavez-Pirson, A., & Peyghambarian, N. (2010). Enhanced terahertz source based on external cavity difference-frequency generation using monolithic single-frequency pulsed fiber lasers. Optics Letters, 35(13), 2170-2172.
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  PMID: 20596183;Abstract: We demonstrate a resonant external cavity approach to enhance narrowband terahertz radiation through differencefrequency generation for the first time (to our knowledge). Two nanosecond laser pulses resonant in an optical cavity interact with a nonlinear crystal to produce a factor of 7 enhancement of terahertz power compared to a single-pass orientation. This external enhancement approach shows promise to significantly increase both terahertz power and conversion efficiency through optical pump pulse enhancement and effective recycling. © 2010 Optical Society of America.
• Petersen, E. B., Shi, W., Nguyen, D. T., Yao, Z., Zong, J., Chavez-Pirson, A., & Peyghambarian, N. (2010). THz source based on external cavity enhanced difference frequency generation by using monolithic singlefrequency pulsed fiber lasers. Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010.
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  Abstract: We demonstrate a resonant cavity approach to enhance narrow band THz radiation. Two nanosecond laser pulses in a cavity interact with a nonlinear crystal to produce 7-fold enhancement of THz power compared to single-pass orientation. © 2010 Optical Society of America.
• Petersen, E. B., Shi, W., Nguyen, D. T., Yao, Z., Zong, J., Chavez-Pirson, A., & Peyghambarian, N. (2010). THz source based on external cavity enhanced difference frequency generation by using monolithic singlefrequency pulsed fiber lasers. Optics InfoBase Conference Papers.
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  Abstract: We demonstrate a resonant cavity approach to enhance narrow band THz radiation. Two nanosecond laser pulses in a cavity interact with a nonlinear crystal to produce 7-fold enhancement of THz power compared to single-pass orientation. © 2010 Optical Society of America.
• Peyghambarian, N. (2010). A better eye in the sky. Photonics Spectra, 44(4).
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  Abstract: Various new technical innovations that provide assistance in battlefield are presented. The Advanced Responsive Tactically Effective Military Imaging spectrometer (ARTEMIS) is intended to supply tactical information, such as the existence of camouflage, disturbed earth, or other signs of enemy activity. Prototypes of digital night-vision goggle, developed by BAE Systems, fuse data from various thermal and low-light sensors to improve situational awareness. A program Super-Resolution Vision System, funded by DARPA, is aimed to develop sighting systems that offer better than diffraction-limited imaging in a field device carried by a soldier. Nasser Peyghambarian, a professor of optics at the University of Arizona in Tucson, has commented on rewritable holograms that could allow three-dimensional rendering of battlefields and other military command-and-control applications.
• Peyghambarian, N. (2010). Imaging system projects holograms in real time. Engineer, NOVEMBER.
• Peyghambarian, N., Blanche, P., Bablumian, A., Voorakaranam, R., Christenson, C., Lin, W., Gu, T., Flores, D., Wang, P., Hsieh, W., Kathaperumal, M., Rachwal, B., Siddiqui, O., Thomas, J., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. N. (2010). Holographic three-dimensional telepresence using large-area photorefractive polymer. Nature, 468(7320).
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  Holography is a technique that is used to display objects or scenes in three dimensions. Such three-dimensional (3D) images, or holograms, can be seen with the unassisted eye and are very similar to how humans see the actual environment surrounding them. The concept of 3D telepresence, a real-time dynamic hologram depicting a scene occurring in a different location, has attracted considerable public interest since it was depicted in the original Star Wars film in 1977. However, the lack of sufficient computational power to produce realistic computer-generated holograms and the absence of large-area and dynamically updatable holographic recording media have prevented realization of the concept. Here we use a holographic stereographic technique and a photorefractive polymer material as the recording medium to demonstrate a holographic display that can refresh images every two seconds. A 50 Hz nanosecond pulsed laser is used to write the holographic pixels. Multicoloured holographic 3D images are produced by using angular multiplexing, and the full parallax display employs spatial multiplexing. 3D telepresence is demonstrated by taking multiple images from one location and transmitting the information via Ethernet to another location where the hologram is printed with the quasi-real-time dynamic 3D display. Further improvements could bring applications in telemedicine, prototyping, advertising, updatable 3D maps and entertainment.
• Peyghambarian, N., Christenson, C. W., Thomas, J., Blanche, P., Voorakaranam, R., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. N. (2010). Grating dynamics in a photorefractive polymer with Alq(3) electron traps. Optics express, 18(9).
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  The electron transporting molecule tris(8-hydroxyquinoline) aluminum (Alq(3)) was added in low concentrations to a photorefractive polymer composite to provide trapping sites for electrons. This sample exhibited larger two-beam coupling gain, higher diffraction efficiency at lower voltages, and an increased dielectric breakdown strength compared to a control sample. The dynamics also revealed the presence of a competing grating, and a bipolar charge transport model is shown to fit the data. Overall, Alq(3) improves the response time, efficiency, and breakdown voltage without a significant increase in absorption or loss of phase stability. This has applications for reflection displays and pulsed writing, where charge trapping and generation are major factors limiting the usefulness of photorefractive polymers.
• Peyghambarian, N., Kieu, K., Jones, R. J., & Peyghambarian, N. N. (2010). High power femtosecond source near 1 micron based on an all-fiber Er-doped mode-locked laser. Optics express, 18(20).
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  We report the design and performance of a high power femtosecond laser source near 1 micron wavelength which is generated from an octave-spanning supercontinuum (SC) pumped by an Er-doped mode-locked laser. The laser system delivers >5W average power at 35MHz repetition rate and 135 fs pulse duration.
• Peyghambarian, N., Marks, R., Mathine, D. L., Peyman, G., Schwiegerling, J., & Peyghambarian, N. N. (2010). Adjustable adaptive compact fluidic phoropter with no mechanical translation of lenses. Optics letters, 35(5).
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  We demonstrate a compact optical phoroptor consisting of adjustable astigmatic and defocus lenses. The lenses are fluidically controlled and allow for an arbitrary refractive error to be corrected without mechanically moving lenses. Shack-Hartmann measurements were used to characterize the optical properties of the individual lenses. The lenses were then assembled into the phoropter and controlled with three separate fluid controls. The phoroptor was verified by correcting the vision of a model eye with an induced refraction error.
• Peyghambarian, N., Valley, P., Mathine, D. L., Dodge, M. R., Schwiegerling, J., Peyman, G., & Peyghambarian, N. N. (2010). Tunable-focus flat liquid-crystal diffractive lens. Optics letters, 35(3).
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  We demonstrate an innovative variable-focus flat liquid-crystal diffractive lens (LCDL) with 95% diffraction efficiency and millisecond switching times using a +/-2.4 V ac input. This lens is based on the electrical modulation of a 3 mum layer of nematic liquid-crystal sandwiched between a Fresnel zone electrode structure and a reference substrate. Each zone is divided into 12 subzones to digitize the phase profiles and define the phase wrapping points. The focusing power can rapidly be switched by electrically changing the number of subzones and re-establishing the wrapping points. Potential applications include zooms with no moving parts and autofocus lenses for compact imaging devices.
• Peyghambarian, N., Valley, P., Reza Dodge, M., Schwiegerling, J., Peyman, G., & Peyghambarian, N. N. (2010). Nonmechanical bifocal zoom telescope. Optics letters, 35(15).
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  We report on a novel zoom lens with no moving parts in the form of a switchable Galilean telescope. This zoom telescope consists of two flat liquid-crystal diffractive lenses with apertures of 10mm that can each take on the focal lengths of -50 and +100cm, with a spacing of 50cm and, hence, a zoom ratio of 4x. The lenses are driven using a low-voltage ac source with 1.6V and exhibit millisecond switching times. The spectral characteristic of this diffractive zoom system is evaluated for light sources of various bandwidths. Potential applications for this technology include a zoom lens with no moving parts for camera phones and medical imaging devices.
• Peyghambarian, N., Zhu, X., Schülzgen, A., Li, H., Wei, H., Moloney, J. V., & Peyghambarian, N. N. (2010). Coherent beam transformations using multimode waveguides. Optics express, 18(7).
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  Physical insights and characteristics of beam transformations based on multimode interference (MMI) in multimode waveguides are illuminated and analyzed. Our calculations show that, utilizing a short piece of cylindrical multimode waveguide, an input Gaussian beam can be readily transformed to frequently desired beams including top-hat, donut-shaped, taper-shaped, and Bessel-like beams in the Fresnel or the Fraunhofer diffraction range, or even in both ranges. This is a consequence of diffractive propagation of the field exiting the waveguide. The performance of the beam shaper based on MMI can be controlled via tailoring the dimensions of the multimode waveguide or changing the signal wavelength. This beam shaping technique is investigated experimentally using monolithic fiber devices consisting of a short piece of multimode fiber (approximately 10 mm long) and a single-mode signal delivery fiber.
• Schneebeli, L., Feldtmann, T., Kira, M., Koch, S. W., & Peyghambarian, N. (2010). Zeno-logic applications of semiconductor quantum dots. Physical Review A - Atomic, Molecular, and Optical Physics, 81(5).
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  Abstract: Microscopic calculations show that CdSe-based semiconductor quantum dots with confined exciton and biexciton states are suitable candidates for Zeno-logic applications. The frequencies of the control and signal fields are chosen to guarantee very high transmission of the individual beams. If both fields are present simultaneously, they are strongly absorbed due to efficient ground-state-to-biexciton transitions. The optical Bloch equations for a three-level quantum-dot model with self-consistent light-matter coupling are solved numerically. The influence of dephasing and/or inhomogeneous dot distributions is analyzed and the conditions for satisfactory device operation are identified. © 2010 The American Physical Society.
• Schülzgen, A., Li, L., Zhu, X., Temyanko, V. L., & Peyghambarian, N. (2010). Micro- And nanostructure induced birefringence in phosphate glass fibers. Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010.
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  Abstract: We demonstrate that microstructures inside the cladding of phosphate fiber as well as sub-wavelength nanostructures inside the fiber core can introduce birefringence in phosphate glass fiber components. © 2010 Optical Society of America.
• Schülzgen, A., Li, L., Zhu, X., Temyanko, V. L., & Peyghambarian, N. (2010). Micro- and Nanostructure Induced Birefringence in Phosphate Glass Fibers. Optics InfoBase Conference Papers.
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  Abstract: We demonstrate that microstructures inside the cladding of phosphate fiber as well as sub-wavelength nanostructures inside the fiber core can introduce birefringence in phosphate glass fiber components. © 2010 Optical Society of America.
• Shi, W., Petersen, E. B., Nguyen, D. T., Yao, Z., Zong, J., Stephen, M. A., Chavez-Pirson, A., & Peyghambarian, N. (2010). Monolithic high SBS threshold pulsed fiber laser and frequency doubling for LIDAR and remote sensing spectroscopy. Proceedings of SPIE - The International Society for Optical Engineering, 7582.
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  Abstract: We report a monolithic high SBS-threshold pulsed fiber laser in MOPA for longer nanosecond pulses with transformlimited linewidth. By using a single mode polarization-maintaining large core 25 μm highly Er/Yb co-doped phosphate fiber in the power amplifier stage, we have achieved the highest peak power of 1.2 kW at 1530 nm for 105 ns pulses with transform-limited linewidth, and with a corresponding pulse energy of about 0.126 mJ. The achieved high-energy pulses were frequency doubled by using a commercial periodically poled lithium niobate (PPLN) crystal, and the highest SHG peak power of 271 W has been achieved for the SHG pulses at 765 nm. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Shi, W., Petersen, E. B., Nguyen, D. T., Zong, J., Yao, Z., Chavez-Pirson, A., & Peyghambarian, N. (2010). Single-frequency pulsed fiber lasers at ∼1.5 μm and fiber-based narrow linewidth THz sources. Proceedings of SPIE - The International Society for Optical Engineering, 7582.
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  Abstract: We have implemented monolithic narrow linewidth single-mode single-frequency pulsed fiber lasers in master oscillator and power amplifier (MOPA) configuration based on highly Er/Yb co-doped phosphate fiber with core size of 25 μm. The narrow linewidth pulsed fiber laser seed has been achieved by directly modulating single-frequency CW fiber laser. An arbitrary waveform generator (AWG) was used to pre-shape the pulse shapes in order to avoid the pulse distortion and the dynamic gain saturation in the cascade fiber amplifiers. Based on the newly developed large core single-mode highly Er/Yb co-doped phosphate fiber in the power amplifier stage, the peak power of single-mode pulses can be scaled to more than 100 kW with transform-limited linewidth and diffraction-limited beam quality. These high power narrow linewidth single-mode fiber laser pulses have been successfully used to generate coherent THz waves based on difference-frequency generation (DFG) in GaSe crystal. The single-pass generated THz peak power can reach 0.12 W. Moreover, we have observed the external cavity enhancement of DFG THz generation by using ZnGeP2 for the first time, and implemented a high spectral resolution THz spectrometer based on the developed fiber-based tunable narrow linewidth THz source. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Shi, W., Petersen, E. B., Nguyen, D. T., Zong, J., Yao, Z., Stephen, M. A., Chavez-Pirson, A., & Peyghambarian, N. (2010). Kilowatt-level peak power monolithic fiber amplifier for single-mode, narrow linewidth 100 ns pulses. Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010.
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  Abstract: We have achieved a peak power of 1.2 kW for 105 ns pulses with transform-limited linewidth by using a SM 25 μm core phosphate fiber in the power amplifier stage of a monolithic MOPA system. © 2010 Optical Society of America.
• Shi, W., Petersen, E. B., Nguyen, D. T., Zong, J., Yao, Z., Stephen, M. A., Chavez-Pirson, A., & Peyghambarian, N. (2010). Kilowatt-level peak power monolithic fiber amplifier for single-mode, narrow linewidth 100 ns pulses. Optics InfoBase Conference Papers.
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  Abstract: We have achieved a peak power of 1.2 kW for 105 ns pulses with transform-limited linewidth by using a SM 25μm core phosphate fiber in the power amplifier stage of a monolithic MOPA system. © 2010 Optical Society of America.
• Shi, W., Petersen, E. B., Yao, Z., Nguyen, D. T., Zong, J., Stephen, M. A., Chavez-Pirson, A., & Peyghambarian, N. (2010). Kilowatt-level stimulated-Brillouin-scattering-threshold monolithic transform-limited 100 ns pulsed fiber laser at 1530 nm. Optics Letters, 35(14), 2418-2420.
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  PMID: 20634849;Abstract: We demonstrate a high-stimulated-Brillouin-scattering-threshold monolithic pulsed fiber laser in a master oscillator power amplifier configuration that can operate over the C band. In the power amplifier stage, we used a newly developed single-mode, polarization maintaining, and highly Er/Yb codoped phosphate fiber with a core diameter of 25 μm. A single-frequency actively Q-switched fiber laser was used to generate pulses in the hundreds of nanoseconds at 1530 nm. We have achieved peak power of 1.2 kW for 105 ns pulses at a repetition rate of 8 kHz, corresponding to a pulse energy of 0.126 mJ, with transform-limited linewidth and diffraction-limited beam quality. © 2010 Optical Society of America.
• Thomas, J., Gangopadhyay, P., Munoz, R., & Peyghambarian, N. (2010). Nanoimprinted photonic devices. Proceedings of SPIE - The International Society for Optical Engineering, 7788.
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  Abstract: We introduce a simple yet efficient approach for nanoimprinting sub-50 nm dimensions starting from a low molecular weight plasticized polymer melt. This technique enabled us to successfully imprint versatile large area nanopatterns with high degrees of fidelity and rational control over the residual layers. The key advantage is its reliability in printing versatile nanostructures and nanophotonic devices doped with organic dyes owing to its low processing temperature. Since nanopatterns can be fabricated easily at low costs, this approach offers an easy pathway for achieving excellent nanoimprinted structures for a variety of photonic, electronic and biological research and applications. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Xiong, L., Hofmann, P., Schülzgen, A., Peyghambarian, N., & Albert, J. (2010). Photo-thermal growth of unsaturated and saturated bragg gratings in phosphate glass fibers. Optics InfoBase Conference Papers.
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  Abstract: We demonstrate that the strong thermal growth of fiber Bragg gratings in phosphate glass fibers at temperatures between 100-250°C requires the seed gratings written using 193 nm light to be overexposed beyond saturation. © 2010 Optical Society of America.
• Yamamoto, M., Wang, P., Tao, G. u., Lin, W., Wanyun, H., Siddiqui, O., Bablumyan, A., Ordyan, A., Blanche, P., Voorakaranam, R., & Peyghambarian, N. (2010). Color rewritable photorefractive large area display material. IDW'10 - Proceedings of the 17th International Display Workshops, 2, 1323-1326.
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  Abstract: Organic polymer-based photorefractive materials which have both better diffraction efficiency and longer grating persistency have been improved. The materials were succeeded in principle-proving concept of highly image-persistent and rewritable holographic display systems. By using materials, we are aiming for developments of holographic display devices such as medical imaging devices. © 2010 ITE and SID.
• Zhu, X., & Peyghambarian, N. (2010). High-power ZBLAN glass fiber lasers: Review and prospect. Advances in OptoElectronics, 2010.
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  Abstract: ZBLAN (ZrF4-BaF2-LaF3-AlF 3-NaF), considered as the most stable heavy metal fluoride glass and the excellent host for rare-earth ions, has been extensively used for efficient and compact ultraviolet, visible, and infrared fiber lasers due to its low intrinsic loss, wide transparency window, and small phonon energy. In this paper, the historical progress and the properties of fluoride glasses and the fabrication of ZBLAN fibers are briefly described. Advances of infrared, upconversion, and supercontinuum ZBLAN fiber lasers are addressed in detail. Finally, constraints on the power scaling of ZBLAN fiber lasers are analyzed and discussed. ZBLAN fiber lasers are showing promise of generating high-power emissions covering from ultraviolet to mid-infrared considering the recent advances in newly designed optical fibers, beam-shaped high-power pump diodes, beam combining techniques, and heat-dissipating technology. © 2010 X. Zhu and N. Peyghambarian.
• Zhu, X., Wang, J., Lau, P., Nguyen, D., Norwood, R. A., & Peyghambarian, N. (2010). Nonlinear optical performance of periodic structures made from composites of polymers and Co₃ O₄ nanoparticles. Applied Physics Letters, 97(9).
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  Abstract: The nonlinear optical performance of specially designed periodic structures made from composites of optical polymers and Co3 O4 nanoparticles is investigated. The refractive indices of the alternating layers are designed to be close and no photonic band gap (PBG) is formed at low power density. Under high power illumination, the index difference becomes large because of the high optical nonlinearities of the Co3 O4 nanoparticles. Consequently, enhanced nonlinear optical performance is obtained with the formation and the strengthening of the PBG. Nonlinear reflection and nonlinear transmission as well as reduced nonlinear threshold are observed in the PBG structures. © 2010 American Institute of Physics.
• Zhu, X., Wang, J., Lau, P., Nguyen, D., Norwood, R. A., Steeves, D., Kimball, B., & Peyghambarian, N. (2010). Nonlinear transmission using highly nonlinear Bragg mirrors. Proceedings of SPIE - The International Society for Optical Engineering, 7599.
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  Abstract: Nonlinear transmission upon the formation of an optically induced photonic band gap (PBG) is demonstrated by using periodic layers of optical polymers doped with highly nonlinear transition metal oxides. The refractive indices of the alternating layers are designed to be close and no PBG is formed at low power densities. Under high power illumination, the index difference becomes large because of the high optical nonlinearities of the transition metal oxides. Consequently, nonlinear transmission is accomplished with the formation and the broadening of the PBG. Compared to typical optical limiters based on a PBG approach, our devices provide a large dynamic range and a broad operation wavelength range. The experiments on a nonlinear Bragg mirror consisting of only 4 pairs of PVA:Co3O4-PVK, each with a layer thickness of 85 nm, show a linear transmittance of greater than 50% throughout the visible, and nonlinear transmission for a 10 ns laser pulse at 523 nm with a threshold of 30 mJ/cm2 and a minimum transmission of about 10%. The minimum transmission reduces to 5% for a 12-pair device. Improving the uniformity of each layer and adding more pairs can result in even lower transmission at high intensities. The threshold can be further reduced through precise design and control of the thickness of each layer. The device and material approach is promising for applications such as protection for broadband detectors and human eyes. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Banerjee, P. P., Cook, G., Evans, D. R., Wofford, J., Blanche, P. -., Thomas, J., & Peyghambarian, N. (2009). Transmission, reflection, and absorption gratings in photorefractive polymers. Proceedings of SPIE - The International Society for Optical Engineering, 7420.
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  Abstract: Two-beam coupling (TBC) in a photorefractive polymer using transmission and reflection geometries is investigated. With drift (due to an applied electric field) and diffusion, a linearized analysis suggests a phase shift between the intensity grating and the induced refractive index grating different from the ideal value of 90 degrees, which is supported by experimental results using a transmission grating geometry. In a self-pumped reflection grating geometry, which is also experimentally studied, the phase shift can be closer to 90 degrees due to a shorter grating period. Absorption and absorption gratings during TBC is also experimentally investigated. © 2009 SPIE.
• DeRose, C. T., Himmelhuber, R., Mathine, D., Norwood, R. A., Luo, J., Jen, A. K., & Peyghambarian, N. (2009). High Δn strip-loaded electro-optic polymer waveguide modulator with low insertion loss. Optics Express, 17(5), 3316-3321.
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  PMID: 19259168;Abstract: We demonstrate a novel electro-optic polymer modulator design which shows a record low optical insertion loss of 5.7 dB at 1550 nm. The modulator consists of a high numerical aperture passive waveguide which is converted to a strip-loaded electro-optic polymer waveguide through refractive index tapers. The device is fabricated using all wet-etch techniques which results in low excess loss from roughness created during fabrication and, employs new low loss passive sol-gel materials. The fabricated device also shows a low half-wave voltage of 2.8 V. © 2009 Optical Society of America.
• Desirena, H., Schülzgen, A., Sabet, S., Ramos-Ortiz, G., de, E., & Peyghambarian, N. (2009). Effect of alkali metal oxides R₂O (R = Li, Na, K, Rb and Cs) and network intermediate MO (M = Zn, Mg, Ba and Pb) in tellurite glasses. Optical Materials, 31(6), 784-789.
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  Abstract: A systematic characterization of optical, chemical and thermo-mechanical properties of R2O-MO-TeO2 glasses as function of alkali metals as network modifiers and network intermediate was performed. Properties such as thermal expansion coefficient (α), glass transition temperature (Tg), refractive index (n), transmittance, chemical durability (DR), density (ρ) and the third-order nonlinear optical susceptibility (χ(3)) were measured and it was found that both components R2O and MO, have great influence on such properties. Experimental results indicate that alkali metals with small ionic radii improve chemical durability (DR) and mechanical (α, Tg) properties. They also increase n and χ(3). Lower thermal expansion coefficient was obtained for Zn and Mg while better chemical durability corresponds to Pb and Zn. © 2008 Elsevier B.V. All rights reserved.
• Enami, Y., Mathine, D., Derose, C. T., Norwood, R. A., Luo, J., Jen, A. K., & Peyghambarian, N. (2009). Hybrid electro-optic polymer/sol-gel waveguide directional coupler switches. Applied Physics Letters, 94(21).
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  Abstract: We report electro-optic (EO) switches using transversely tapered hybrid EO/sol-gel waveguide directional couplers. The length of the active region critically reduces to 1.5 mm with transverse tapers, which is shorter by a factor of 5 than the active region with vertical tapers. The transitions are performed from a sol-gel core to two EO polymer cores with gradual index changes using gray-scaled photobleaching. The device shows the lowest switching voltage and an active length product (Vs La) of 2.9 V cm with a guest-host EO polymer AJLS102, compared to hybrid waveguide switches and modulators with vertical taper and higher EO coefficients. © 2009 American Institute of Physics.
• Gangopadhyay, P., Koeckelberghs, G., Lopez-Santiago, A., Norwood, R. A., Peyghambarian, N., & Persoons, A. (2009). Magnetic and magneto optic properties of substituted polythiophenes. Proceedings of SPIE - The International Society for Optical Engineering, 7413.
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  Abstract: We report on our recent observation of magnetic and magneto optic properties of regioregular substituted polythiophenes. The relevance of existing mechanisms within the classical limit in cognizance of our recent magnetic and MO measurements on a set of π-conjugated polymer is also discussed.
• Haji-saeed, B., Khoury, J., Woods, C. L., Kierstead, J., & Peyghambarian, N. (2009). Nonlinear optical dynamic range compression with thin-film organic photorefractive material. Proceedings of SPIE - The International Society for Optical Engineering, 7340.
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  Abstract: Nonlinear information processing via two-beam coupling using thin-film organic photorefractive material is demonstrated. The organic material is found to possess superior response time and resolution compared to photorefractive bulk material. The possibility of designing dynamic range compression deconvolution for restoring blurred images embedded in a noisy environment is also demonstrated. © 2009 SPIE.
• Harun, S. W., Hofmann, P., Schülzgen, A., Li, L., Nguyen, D., Spiegelberg, C., Rogojan, R. M., Laronche, A., Albert, J., Ahmad, H., & Peyghambarian, N. (2009). An Erbium -Ytterbium DFB laser with a simple and compact structure. Journal of Physics: Conference Series, 187.
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  Abstract: A distributed feedback fiber (DFB) laser operating at 1540 nm having more than 45 dB signal to amplified spontaneous emission ratio with a simple and compact structure is introduced. The DFB laser consists of 45 mm long highly Er-Yb co-doped phosphate glass fiber with a grating structure inside the gain medium. The laser emission is stable, but the power is still relatively lower due to un-optimized grating structure. © 2009 IOP Publishing Ltd.
• Jianfeng, W. u., Yao, Z., Zong, J., Chavez-Pirson, A., Peyghambarian, N., & Jirong, Y. u. (2009). Single frequency fiber laser at 2.05 μm based on Ho-doped germanate glass fiber. Proceedings of SPIE - The International Society for Optical Engineering, 7195.
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  Abstract: A single frequency fiber laser operating near 2 micron with over 50 mW output power has been demonstrated by using a short piece of newly developed single mode holmium-doped germanate glass fiber. Laser from 2004 nm to 2083 nm was demonstrated from a short Ho-doped fiber laser cavity. A heavily thulium-doped germanate fiber was used as an in-band pump source for the holmium-doped fiber laser. The single frequency fiber laser can be thermally tuned. © 2009 SPIE.
• Leigh, M. A., Shi, W., Zong, J., Yao, Z., Jiang, S., & Peyghambarian, N. (2009). Narrowband pulsed THz source using eyesafe region fiber lasers and a nonlinear crystal. IEEE Photonics Technology Letters, 21(1), 27-29.
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  Abstract: We report a high-power single-frequency fiber laser system in the eyesafe wavelength region that pumps a GaSe crystal through difference frequency generation, producing narrowband terahertz (THz). Two single-frequency continuous-wave fiber seed lasers are modulated, then amplified with a three-stage single-mode amplifier. The resulting pulses are transform-limited and high power, producing a peak THz power of 26.4 mW with narrow linewidth. This is significantly higher than earlier THz sources based on narrowband fiber lasers in the eyesafe region. © 2009 IEEE.
• Lopez-Santiago, A., Gangopadhyay, P., Thomas, J., Norwood, R. A., & Peyghambarian, N. (2009). All-optical magnetometer based on magnetite core-polymer shell nanocomposite material. Optics InfoBase Conference Papers.
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  Abstract: An all-optical magnetometer has been constructed based on magnetite core polymer ell nanocomposite material. A noise equivalent magnetic field sensitivity of 5 nT/√Hz was served using a 1 μT 500 Hz control magnetic field. © 2009 Optical Society of America.
• Lopez-Santiago, A., Gangopadhyay, P., Thomas, J., Norwood, R. A., Persoons, A., & Peyghambarian, N. (2009). Faraday rotation in magnetite-polymethylmethacrylate core-shell nanocomposites with high optical quality. Applied Physics Letters, 95(14).
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  Abstract: Wavelength dependent Faraday rotation measured at room temperature in a polymer containing varying concentrations of crosslinked magnetite core poly(3-methyl)methacrylate (PMMA) shell nanocomposite particles is reported. The magnitude of the FR in these composites appears to be strongly dependent on the concentration of the particles, the wavelength of measurement, and the size and shape of the nanoparticles. Comparison of the figure of merit of 2.1°in these core-shell nanocomposites to that of 4.2°for yttrium iron garnet at 980 nm indicates that these nanocomposites may find applications in various magnetic and magneto-optic sensors and devices. © 2009 American Institute of Physics.
• Norwood, R. A., Derose, C. T., Himmelhuber, R., Peyghambarian, N., Wang, J., Li, L., Ouchen, F., & Grote, J. G. (2009). Dielectric and electrical properties of sol-gel/DNA blends. Proceedings of SPIE - The International Society for Optical Engineering, 7403.
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  Abstract: We investigate the dielectric and electrical properties of sol-gel/DNA-CTMA blends, with particular interest in capacitor applications in energy storage. Methacryloyloxypropyltrimethoxysilane (MAPTMS) was the sol-gel precursor, and DNA-CTMA was blended in to the resulting sol-gel at 5 weight%. The blend was then tested for its dielectric properties and dielectric breakdown strength; at frequencies below 10kHz the blend was found to have a dielectric constant in the range of 7.5, while the breakdown strength was greater than 800 V/μm, an exceptional value. We discuss these results as well as other aspects of the dielectric and electrical properties of these blends. © 2009 SPIE.
• Peyghambarian, N. (2009). Large area 3-D updateable holographic displays using photorefractive polymers. Optics InfoBase Conference Papers.
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  Abstract: Photorefractive polymers are shown to be suitable for large area dynamic 3D holographic display. We have demonstrated 6"x 6"updateable 3D displays that can be erased and rewritten many times. © 2009 OSA.
• Peyghambarian, N., DeRose, C. T., Himmelhuber, R., Mathine, D., Norwood, R. A., Luo, J., Jen, A. K., & Peyghambarian, N. N. (2009). High Deltan strip-loaded electro-optic polymer waveguide modulator with low insertion loss. Optics express, 17(5).
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  We demonstrate a novel electro-optic polymer modulator design which shows a record low optical insertion loss of 5.7 dB at 1550 nm. The modulator consists of a high numerical aperture passive waveguide which is converted to a strip-loaded electro-optic polymer waveguide through refractive index tapers. The device is fabricated using all wet-etch techniques which results in low excess loss from roughness created during fabrication and, employs new low loss passive sol-gel materials. The fabricated device also shows a low half-wave voltage of 2.8 V.
• Peyghambarian, N., Marks, R., Mathine, D. L., Peyman, G., Schwiegerling, J., & Peyghambarian, N. N. (2009). Adjustable fluidic lenses for ophthalmic corrections. Optics letters, 34(4).
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  We report on two fluidic lenses that have been developed for ophthalmic applications. The lenses use a circular aperture to demonstrate optical powers between -20 and +20 D and a rectangular aperture to demonstrate astigmatism with values ranging from 0 to 8 D. Measurements of image quality were made with the fluidic lens using a model eye. Both lenses were variable and controllable by adjusting the fluid volume of the lens. To the best of our knowledge this is the first demonstration of a continuously variable lens for control of astigmatism.
• Peyghambarian, N., Marks, R., Mathine, D. L., Schwiegerling, J., Peyman, G., & Peyghambarian, N. N. (2009). Astigmatism and defocus wavefront correction via Zernike modes produced with fluidic lenses. Applied optics, 48(19).
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  Fluidic lenses have been developed for ophthalmic applications with continuously varying optical powers for second order Zernike modes. Continuously varying corrections for both myopic and hyperopic defocus have been demonstrated over a range of three diopters using a fluidic lens with a circular retaining aperture. Likewise, a six diopter range of astigmatism has been continuously corrected using fluidic lenses with rectangular apertures. Imaging results have been characterized using a model eye.
• Peyghambarian, N., Sheng, C., Norwood, R. A., Wang, J., Thomas, J., Steeves, D., Kimball, B., & Peyghambarian, N. N. (2009). Nonlinear optical transmission of lead phthalocyanine-doped nematic liquid crystal composites for multiscale nonlinear switching from nanosecond to continuous wave. Applied optics, 48(14).
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  We have formulated composites of lead (II) tetrakis (4-cumylphenoxy) phthalocyanine (PbTCPc) doped into nematic liquid crystal (LC), 4(')-pentyl-4-biphenylcarbonitrile (5-CB), that has received a 90 degree twisted alignment and investigated the nonlinear transmission properties using both pulsed (Nd:YLF 524 nm, 5 ns) and cw (532 nm) lasers. In the nanosecond regime, this compound is a reverse saturable absorber performing similarly to low-concentration solutions of PbTCPc. Under cw conditions, we observe optically self-activated polarization switching with low threshold input energy. Our results suggest the potential for an all-optical switch working from the nanosecond time scale to cw.
• Schülzgen, A., Li, L., Zhu, X., Albert, J., & Peyghambarian, N. (2009). Recent advances in phosphate glass fiber lasers. 2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum Electronics and Laser Science Conference, CLEO/QELS 2009.
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  Abstract: Phosphate glasses are excellent host materials for lasers using rare-earth ion transitions. Combining highly-doped phosphate glasses and advanced fiber drawing techniques, we developed phosphate glass fiber lasers and will review recent advances in their performance. © 2009 Optical Society of America.
• Schülzgen, A., Li, L., Zhu, X., Albert, J., & Peyghambarian, N. (2009). Recent advances in phosphate glass fiber lasers. Optics InfoBase Conference Papers.
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  Abstract: Phosphate glasses are excellent host materials for lasers using rare-earth ion transitions. Combining highly-doped phosphate glasses and advanced fiber drawing techniques, we developed phosphate glass fiber lasers and will review recent advances in their performance. © 2009 Optical Society of America.
• Sheng, C. X., Norwood, R. A., Wang, J., Thomas, J., Steeves, D., Kimball, B., & Peyghambarian, N. (2009). Nonlinear optical transmission of lead phthalocyanine- Doped nematic liquid crystal composites for multiscale nonlinear switching from nanosecond to continuous wave. Applied Optics, 48(14), 2731-2734.
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  PMID: 19424396;Abstract: We have formulated composites of lead (II) tetrakis (4-cumylphenoxy) phthalocyanine (PbTCPc) doped into nematic liquid crystal (LC), 4'-pentyl-4-biphenylcarbonitrile (5-CB), that has received a 90° twisted alignment and investigated the nonlinear transmission properties using both pulsed (Nd:YLF 524 nm, 5 ns) and cw (532 nm) lasers. In the nanosecond regime, this compound is a reverse saturable absorber performing similarly to low-concentration solutions of PbTCPc. Under cw conditions, we observe optically self-activated polarization switching with low threshold input energy. Our results suggest the potential for an all-optical switch working from the nanosecond time scale to cw. © 2009 Optical Society of America.
• Shi, W., Leigh, M. A., Zong, J., Yao, Z., Nguyen, D. T., Chavez-Pirson, A., & Peyghambarian, N. (2009). High-Power all-fiber-based narrow-linewidth single-mode fiber laser pulses in the C-band and frequency conversion to THz generation. IEEE Journal on Selected Topics in Quantum Electronics, 15(2), 377-384.
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  Abstract: Based on highly Er/Yb codoped phosphate fibers, we have implemented all-fiber-based narrow-linewidth single-mode (SM) pulsed fiber lasers in master oscillator and power amplifier configuration. Two approaches were used to achieve the narrow-linewidth pulsed fiber laser seeds: 1) an all-fiber-based active $Q$-switched fiber laser using an actuator and 2) a directly modulated single-frequency continuous-wave fiber laser. Both the fiber laser seed pulses from the two approaches have the transform-limited spectral linewidth. Based on a newly developed large-core SM highly Er/Yb codoped phosphate fiber, the peak power of SM pulses can be scaled to more than 50 kW with transform-limited linewidth and diffraction-limited beam quality. These high-power narrow-linewidth SM fiber laser pulses have been successfully used to generate coherent terahertz (THz) waves based on parametric processes in a nonlinear optical crystal. The peak power of this fiber-based THz source can reach 26.4 mW. © 2009 IEEE.
• Shi, W., Petersen, E. B., Leigh, M., Zong, J., Yao, Z., & Peyghambarian, N. (2009). High SBS-threshold single-mode single-frequency monolithic pulsed fiber laser in the C-band. Optics Express, 17(10), 8237-8245.
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  PMID: 19434156;Abstract: We report a high SBS-threshold, single-frequency, single-mode, polarization maintaining (PM) monolithic pulsed fiber laser source in master oscillator and power amplifier (MOPA) configuration that can operate over the C-band. In order to achieve a narrow transform-limited linewidth for pulses longer than 100 ns, we use a single-frequency Q-switched fiber laser seed, which itself can be seamlessly tuned up to 1.24 (is. The Q-switched pulses are amplified in the power amplifier stage of MOPA using a high SBS threshold single-mode PM large core highly Er/Yb co-doped phosphate glass fiber (LC-EYPhF). This seed and amplifier combination represents the first monolithic, all-fiber implementation of a single-frequency pulsed laser with the highest pulse energy of 54 (J and peak power of 332 W for 153-ns pulses at 1538 nm. © 2009 Optical Society of America.
• Shi, W., Petersen, E. B., Leigh, M., Zong, J., Yao, Z., Chavez-Pirson, A., & Peyghambarian, N. (2009). High-energy single-mode single-frequency all-fiber laser pulses covering C-band based on highly co-doped phosphate glass fibers. Proceedings of SPIE - The International Society for Optical Engineering, 7195.
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  Abstract: We report a new pulsed, narrow linewidth, single-mode, polarization maintaining (PM) all-fiber laser source in master oscillator and power amplifier (MOPA) configuration that can operate over the C-band. The single-frequency pulsed fiber laser seed was achieved by actively Q-switching a fiber laser using a piezo, with a wide pulse duration tuning range of 7.5 ns - 1.24 μs. We use single-mode PM large core highly Er/Yb co-doped phosphate glass fiber (LC-EYPhF) in the power amplifier stage of MOPA to achieve 54 μJ/pulse for 153-ns pulses at 1538 nm with repetition rate of 20 kHz and an estimated linewidth of ~ 5 MHz. © 2009 SPIE.
• Shi, W., Petersen, E. B., Meair, J., Nguyen, D. T., Zong, J., Yao, Z., Chavez-Pirson, A., & Peyghambarian, N. (2009). Fiber-based THz sources based on monolithic single-frequency pulsed fiber lasers in the C-band. 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009.
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  Abstract: Compact, efficient, narrow linewidth, fiber based THz sources have been achieved by using the monolithic high power single-frequency pulsed fiber lasers in MOPA based on difference-frequency generation (DFG) in nonlinear optical crystals. We have observed the external cavity enhancement of DFG THz generation by using ZnGeP2 for the first time. ©2009 Optical Society of America.
• Shi, W., Petersen, E. B., Meair, J., Nguyen, D. T., Zong, J., Yao, Z., Chavez-Pirson, A., & Peyghambarian, N. (2009). Fiber-based THz sources based on monolithic single-frequency pulsed fiber lasers in the C-band. Proceedings of SPIE - The International Society for Optical Engineering, 7631.
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  Abstract: Compact, efficient, narrow linewidth, fiber based THz sources have been achieved by using the monolithic high power single-frequency pulsed fiber lasers in MOPA based on difference-frequency generation (DFG) in nonlinear optical crystals. We have observed the external cavity enhancement of DFG THz generation by using ZnGeP2 for the first time, and implemented a high spectral resolution THz spectrometer based on the developed fiber-based tunable narrow linewidth THz source. © 2009 SPIE-OSA-IEEE.
• Suzuki, S., Schülzgen, A., & Peyghambarian, N. (2009). Single-mode fiber laser based on core-cladding mode conversion. European Conference on Optical Communication, ECOC.
• Tay, S., Kropachev, A., Araci, I. E., Skotheim, T., Norwood, R. A., & Peyghambarian, N. (2009). Plasmonic thermal IR emitters based on nanoamorphous carbon. Applied Physics Letters, 94(7).
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  Abstract: The development of plasmonic narrow-band thermal mid-IR emitters made from a conducting amorphous carbon composite is shown. These IR emitters have greatly improved thermal and mechanical stability compared to metallic emitters as they can be operated at 600 °C in air without any degradation in performance. The emitted thermal radiation has a bandwidth of 0.5 μm and can be set to the desired wavelength from 3 to 15 μm by changing the surface periodicity. The periodically patterned devices have in-band emissivities significantly exceeding that of the non-patterned devices, constituting simple yet efficient radiation sources at this important wavelength range. © 2009 American Institute of Physics.
• Thomas, J., Norwood, R. A., & Peyghambarian, N. (2009). Non-linear optical polymers for photorefractive applications. Journal of Materials Chemistry, 19(40), 7476-7489.
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  Abstract: Photorefractive materials can be used to record and erase holograms many times without the need for chemical processing. This places photorefractive materials at the cutting edge for use in updatable holographic display applications. This feature article reviews the basic principles of polymer photorefractivity and the properties of a newly developed bis-triarylamine side-chain photorefractive polymer sensitive at visible and near-infrared wavelengths. The photorefractive composites developed using this polymer exhibit stable dynamic properties under continuous operation combined with video-rate compatible dynamics, and long shelf lifetimes. Recent improvements in the polymer compositions have led to the development of an updateable holographic 3D display, capable of recording and displaying new images every few minutes. © 2009 The Royal Society of Chemistry.
• Zhu, X., Schülzgen, A., Li, L., & Peyghambarian, N. (2009). Generation of controllable nondiffracting beams using multimode optical fibers. Applied Physics Letters, 94(20).
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  Abstract: A method of generating nondiffracting beams using multimode optical fibers is reported. When a large-core multimode fiber is spliced onto a piece of single-mode fiber, only linearly polarized (LP0,n) modes are excited inside the multimode fiber segment because of mode orthogonality and on-axis excitation. Since the excited L P0,n modes are actually Bessel fields with different transverse wave vectors truncated by the core of the multimode fiber, the beam exiting the multimode fiber facet can form a variety of readily controllable and nearly nondiffracting optical patterns resulting from interference of apertured Bessel fields. © 2009 American Institute of Physics.
• Blanche, P., Tay, S., Voorakaranam, R., Saint-Hilaire, P., Christenson, C., Tao, G. u., Lin, W., Flores, D., Wang, P., Yamamoto, M., Thomas, J., Norwood, R. A., & Peyghambarian, N. (2008). An updatable holographic display for 3D visualization. IEEE/OSA Journal of Display Technology, 4(4), 424-430.
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  Abstract: Among the various methods to produce three-dimensional (3D) images, holography occupies a special niche. Indeed, holograms provide highly realistic 3D images with a large viewing angle capability without the need for special eyewear. Such characteristics make them valuable tools for a wide range of applications such as medical, industrial, military, and entertainment imaging. To be suitable for an updatable holographic display, a material needs to have a high diffraction efficiency, fast writing time, hours of image persistence, capability for rapid erasure, and the potential for large display area - a combination of properties that has not been realized before. Currently, there exist several media for recording holograms like photopolymers, silver halide films or dichromated gelatin, to name a few. However, in all of these media, the image is permanently written and cannot be refreshed. There also exist dynamic 3D display systems based on acousto-optic materials, liquid-crystals or microelectromechanical systems (MEMS), however they rely on massive wavefront computations that limit their image size capability. Inorganic crystals for hologram recording such as photorefractive crystals are extremely difficult to grow to larger than a few cubic centimeters in volume.Photorefractive polymers are dynamic holographic recording materials that allow for updating of images. They have been investigated over the last decade and have a wide range of applications including optical correlation, imaging through scattering media, and optical communication. Here, we report the details of the achievement of the first updatable holographic 3D display based on photorefractive polymers. With a 4 × 4 in2 size, this is the largest photorefractive 3D display to date and is capable of recording and displaying new images every few minutes. The holograms can be viewed for several hours without the need for refreshing, and can be completely erased and updated whenever desired. © 2008 IEEE.
• DeRose, C. T., Mathine, D., Enami, Y., Norwood, R. A., Luo, J. D., Jen, A. K., & Peyghambarian, N. (2008). Electro-optic polymer waveguide modulators with refractive index tapers leading to low coupling loss and a high confinement factor. 2008 Conference on Quantum Electronics and Laser Science Conference on Lasers and Electro-Optics, CLEO/QELS.
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  Abstract: A new design of a hybrid electro-optic polymer waveguide modulator is demonstrated that uses grayscale lithography to create refractive index tapers by photobleaching. It leads to a device with a half-wave voltage of 1.9 V, modulation efficiency of 15 dB and a fiber to lens insertion loss of 11.6 dB using 20 wt. % AJLS102. © 2008 IEEE.
• DeRose, C. T., Mathine, D., Enami, Y., Norwood, R. A., Luo, J., Jen, A. K., & Peyghambarian, N. (2008). Electrooptic polymer modulator with single-mode to multimode waveguide transitions. IEEE Photonics Technology Letters, 20(12), 1051-1053.
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  Abstract: Grayscale lithography has been used to create refractive index (RI) tapers in an electrooptic (EO) polymer modulator. These RI tapers are used to convert a passive single-mode photobleached polymer waveguide to the fundamental mode of an unbleached, active multimode polymer waveguide. The benefits of this modulator design include a coupling loss reduction of 2.6 dB per interface and an increased confinement factor of 0.83. Using this design, an EO polymer modulator was fabricated with a halfwave voltage of 1.9 V, modulation extinction ratio of 15 dB, and a fiber to lens insertion loss of 11.6 dB. © 2008 IEEE.
• Desirena, H., De, E., Shulzgen, A., Shabet, S., & Peyghambarian, N. (2008). Er³⁺ and Yb³⁺ concentration effect in the spectroscopic properties and energy transfer in Yb³⁺/Er³⁺ codoped tellurite glasses. Journal of Physics D: Applied Physics, 41(9).
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  Abstract: Spectroscopic properties of Yb3+/Er3+ codoped tellurite glasses as a function of Er3+ and Yb3+ concentration have been investigated. Under 970 nm excitation three strong up-conversion emission bands centred at 525, 546 and 656 nm were observed, and the characteristic near infrared emission band was centred at 1.53 νm. With fluorescence and radiative lifetime the quantum efficiency (QE) of infrared (1.53 νm) and visible upconversion (546 and 660 nm) emissions was calculated. The maximum stimulated emission cross section for 4I13/2 → 4I15/2 transition of Er3+ is 9.7 × 10-21 cm2 for 3/0.5 mol%. The energy transfer (ET) efficiency from Yb3+ to Er3+ (4F5/2) + (4I15/2) → (4 F7/2) + ( 4I13/2) was calculated, being the maximum ET of 69% for 0.5 mol% of Er3+ with 4.5 mol% of Yb3+. The results indicate that both ET and QE depend mostly on Er3+ rather than on Yb3+ concentration. © 2008 IOP Publishing Ltd.
• Enami, Y., Mathine, D., DeRose, C. T., Norwood, R. A., Peyghambarian, N., Luo, J., & Jen, A. K. (2008). Novel transversely tapered hybrid electro-optic polymer/sol-gel waveguide modulators. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 640-641.
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  Abstract: A proposed hybrid modulator structure reduces both the optical loss and half wave voltage (Vπ). A sol-gel waveguide core transversely sandwiched between electro-optic (EO) polymer cores without Y-branches to enable an adiabatic transition with higher mode confinement. ©2008 IEEE.
• Enami, Y., Mathine, D., Derose, C. T., Norwood, R. A., Luo, J., Jen, A. K., & Peyghambarian, N. (2008). Transversely tapered hybrid electro-optic polymer/sol-gel Mach-Zehnder waveguide modulators. Applied Physics Letters, 92(19).
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  Abstract: We show results of a proposed hybrid modulator structure that reduces both the optical loss and half wave voltage (Vπ). A sol-gel waveguide core transversely sandwiched between two Mach-Zehnder arms of electro-optic (EO) polymer cores enables an adiabatic transverse transition between the sol-gel and the EO polymer cores without the need for Y branches. The undercladding thickness is reduced to 3.7 μm with negligible further optical loss from the bottom electrode. EO modulation with Vπ of 1.8 V at 1550 nm is demonstrated using a guest-host EO polymer, with an optical insertion loss of 13.7 dB in the transverse magnetic mode. © 2008 American Institute of Physics.
• Gangopadhyay, P., Voorakaranam, R., Lopez-Santiago, A., Foerier, S., Thomas, J., Norwood, R. A., Persoons, A., & Peyghambarian, N. (2008). Faraday rotation measurements on thin films of regioregular alkyl-substituted polythiophene derivatives. Journal of Physical Chemistry C, 112(21), 8032-8037.
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  Abstract: The authors describe a magneto-optic measurement system for the determination of Faraday rotation from ultrathin films relative to a substrate reference. The setup is intrinsically immune to reciprocal effects such as circular birefringence and thermal fluctuations. Faraday rotation measurements on thin films of 3-hexyl and 3-dodecyl derivatives of regioregular polythiophene are reported. The authors show that the Faraday rotation from these films is largely dependent on the supramolecular organization within the the films of these polymers. © 2008 American Chemical Society.
• Himmelhuber, R., DeRose, C. C., Norwood, R. A., & Peyghambarian, N. (2008). UV-patternable inorganic-organic hybrid materials tailored for use in electro-optic modulators. Proceedings of SPIE - The International Society for Optical Engineering, 7049.
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  Abstract: Passive sol-gel materials play an important role in the development of electro-optic(EO) polymer-based modulators, because of their variety of available refractive indices. They can be used to form passive waveguide transitions to minimize coupling loss or as cladding layers for the EO polymer. The demands for these two applications are different. For waveguide transitions the most important factor is the optical loss. Cladding layers should have a relatively high conductivity at elevated temperatures to improve poling efficiency. Both demands are addressed in this study. The synthesis of low loss (down to 0.45 dB/cm) sol-gel materials is shown. Slab waveguides as well as ridge waveguides were fabricated and characterized by liquid prism measurements and cut-back loss measurements, respectively. For use in cladding layers surrounding the EO polymer, materials with higher conductivity were developed. The conductivity of the materials was increased, (3.10-9 S/m) through the use of a silane, which allows in situ formation of proton donating functionalities. All developed materials can be used as solvent free resins, which enables classic photolithography as well as patterning by UV-imprinting. The available refractive index range (at 1.55 μm) is from 1.495 to 1.562.
• Kaneda, Y., Peyghambarian, N., Miyazono, K., Shimatani, H., Honda, Y., Yoshimura, M., Mori, Y., Kitaoka, Y., & Sasaki, T. (2008). All-solid-state sub-200-nm pulsed deep ultraviolet source. 2008 Conference on Quantum Electronics and Laser Science Conference on Lasers and Electro-Optics, CLEO/QELS.
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  Abstract: Using a diode-pumped Q-switched Nd:YAG laser as the pump source, 198.5-nm was constructed. With 1.15 W of average power at 1064 nm, 12 mW of average output power was obtained at 198.5 nm. © 2008 Optical Society of America.
• Kaneda, Y., Peyghambarian, N., Miyazono, K., Shimatani, H., Honda, Y., Yoshimura, M., Mori, Y., Kitaoka, Y., & Sasaki, T. (2008). Improved efficiency of a pulsed optical parametric oscillator by delayed double-pass pump. Optics Letters, 33(3), 231-233.
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  PMID: 18246138;Abstract: By delaying the second pass of the pump of a singly resonant optical parametric oscillator, the conversion efficiency can be improved. We show the experimental results of an intracavity-doubled singly resonant parametric oscillator pumped by a Q-switched laser. Using 0.49 mJ of pump energy at 532 nm from a diodepumped Nd:YAG laser, 0.085 mJ of 488 nm was obtained with the optimum delay for the second pass of the pump, giving a conversion efficiency of 17%. The improvement over the case of a single-pass pump was 85%, and the improvement over the double-pass pump with a small delay was 40%. © 2008 Optical Society of America.
• Kaneda, Y., Peyghambarian, N., Miyazono, K., Shimatani, H., Honda, Y., Yoshimura, M., Mori, Y., Kitaoka, Y., & Sasaki, T. (2008). Optical parametric oscillator with delayed double-pass pump and deep-UV generation by its second harmonic. Advanced Solid-State Photonics, ASSP 2008, MC28.
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  Abstract: Using 0.49 mJ of pump energy at 532 nm from a DPSS for an intracavity-doubled SRO with delayed double-pass pump, 0.085 mJ at 488 nm and 0.018 mJ in deep UV were obtained. © 2008 Optical Society of America.
• Leigh, M., Shi, W., Zong, J., Yao, Z., Jiang, S., & Peyghambarian, N. (2008). High peak power single frequency pulses using a short polarization- maintaining phosphate glass fiber with a large core. Applied Physics Letters, 92(18).
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  Abstract: We report a high power, single frequency 1.5 μm pulsed fiber master oscillator-power amplifier laser source using a large core, polarization- maintaining phosphate glass fiber. The phosphate glass fiber produces high powers with low nonlinearities using high Er-Yb codoping and short length. Using this fiber, we were able to generate single frequency pulses with peak powers up to 51.5 kW. This is the highest reported peak pulse power for eye safe single frequency fiber laser systems. © 2008 American Institute of Physics.
• Nguyen, D. T., Kwong, N. H., Binder, R., Norwood, R., & Peyghambarian, N. (2008). Optical limiting in Bragg-spaced semiconductor quantum wells. 2008 Conference on Quantum Electronics and Laser Science Conference on Lasers and Electro-Optics, CLEO/QELS.
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  Abstract: We propose a new mechanism for optical limiting in which nonlinear absorption and nonlinear reflection act in concert. The mechanism is based on the light-induced shift of the band gap in Bragg-spaced semiconductor quantum wells. © 2008 Optical Society of America.
• Nguyen, D. T., Kwong, N. H., Binder, R., Norwood, R., & Peyghambarian, N. (2008). Optical limiting in bragg-spaced semiconductor quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series.
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  Abstract: We propose a new mechanism for optical limiting in which nonlinear absorption and nonlinear reflection act in concert. The mechanism is based on the light-induced shift of the band gap in Bragg-spaced semiconductor quantum wells. © 2008 Optical Society of America.
• Nguyen, D. T., Sheng, C., Thomas, J., Norwood, R., Kimball, B., Steeves, D. M., & Peyghambarian, N. (2008). Observation of nonlinear transmission enhancement in cavities filled with nonlinear organic materials. Applied Optics, 47(31), 5777-5783.
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  PMID: 19122719;Abstract: We show experimental and theoretical results for enhancement of nonlinear transmission (NT) in moderate finesse cavities filled with nonlinear organic materials (NLOM). Our design for enhancement of nonlinear transmission using micro NLOM cavities compared with reference samples of the same material show that single cavities can enhance the nonlinear response by a factor of 10 or greater under high-absorption conditions. Further enhancement can be achieved in multiple-cavity structures. Other advantages of the cavity structures for nonlinear transmission, such as a higher damage threshold and a broader NT band, are also discussed. Our initial experimental results show a threefold reduction in the nonlinear threshold fluence in a single cavity device compared directly to an identical sample without mirrors, in qualitative agreement with our calculations. © 2008 Optical Society of America.
• Peyghambarian, N., Chen, S., Han, L., Schülzgen, A., Li, H., Li, L., Moloney, J. V., & Peyghambarian, N. N. (2008). Local electric field enhancement and polarization effects in a surface-enhanced Raman scattering fiber sensor with chessboard nanostructure. Optics express, 16(17).
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  A surface-enhanced Raman scattering fiber sensor with chessboard nanostructure on a cleaved fiber facet is studied by finite-difference time-domain method. Surface plasmons at the metal coated nanostructured fiber facet can be effectively excited and strong local electric field enhancement is obtained. Studies on the influence of light polarization demonstrate a large polarization dependence of the field enhancement factor while the polarization effects on the plasmon resonance wavelength are relatively small.
• Peyghambarian, N., Enami, Y., DeRose, C. T., Mathine, D., Norwood, R. A., Luo, J., & Jen, A. K. (2008). Hybrid electro optic modulators with subvolt drive voltages. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 185-.
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  Abstract: Hybrid organic-solgel nonlinear materials are being investigated as high speed low voltage modulators. This paper provides a summary of our recent results in this area. Various design structures will be reviewed. We have also demonstrated near ∼100% poling efficiency in several generations of hybrid electro-optic (EO) polymer/sol-gel waveguide modulators, using crosslinkable and guest-host EO polymers. In these devices, the EO polymer was poled using an electrically conductive sol-gel cladding in the hybrid modulator, such that the poling voltage was completely applied to the EO polymer layer. Stable long-term operation is preferred for industrial applications. The hybrid polymeric modulator has the additional benefits of stable and low loss optical coupling to standard optical fiber, and stable waveguiding, since the thermally and optically stable sol-gel core in the passive regions plays the primary role in optical coupling. Fine refractive index control of the EO polymer is not required in the hybrid modulator, which is another advantage for long-term stability. In the hybrid approach, whenever the EO polymer core has higher refractive index (e.g. 1.63-1.68) than the sol-gel core (1.50), coupled and waveguided light in the sol-gel core can be adiabatically transferred to the EO polymer core and back through vertical tapers in the sol-gel. We will review our recent results including demonstration of a Vπ of 0.65V at 1550nm. ©2008 IEEE.
• Peyghambarian, N., Nguyen, D. T., Sheng, C., Thomas, J., Norwood, R., Kimball, B., Steeves, D. M., & Peyghambarian, N. N. (2008). Observation of nonlinear transmission enhancement in cavities filled with nonlinear organic materials. Applied optics, 47(31).
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  We show experimental and theoretical results for enhancement of nonlinear transmission (NT) in moderate finesse cavities filled with nonlinear organic materials (NLOM). Our design for enhancement of nonlinear transmission using micro NLOM cavities compared with reference samples of the same material show that single cavities can enhance the nonlinear response by a factor of 10 or greater under high-absorption conditions. Further enhancement can be achieved in multiple-cavity structures. Other advantages of the cavity structures for nonlinear transmission, such as a higher damage threshold and a broader NT band, are also discussed. Our initial experimental results show a threefold reduction in the nonlinear threshold fluence in a single cavity device compared directly to an identical sample without mirrors, in qualitative agreement with our calculations.
• Peyghambarian, N., Schülzgen, A., Li, L., Nguyen, D., Spiegelberg, C., Rogojan, R. M., Laronche, A., Albert, J., & Peyghambarian, N. N. (2008). Distributed feedback fiber laser pumped by multimode laser diodes. Optics letters, 33(6).
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  A distributed feedback fiber laser made of highly Er-Yb codoped phosphate glass fiber has been demonstrated experimentally. Efficient pump absorption allows for multimode pumping into the cladding of the active fiber. Output powers up to 160 mW have been achieved. The 35 mm long fiber laser device emits with >50 dB side mode suppression ratio.
• Peyghambarian, N., Sheng, C., Norwood, R. A., Wang, J., Thomas, J., Wu, Y., Zheng, Z., Tabirian, N., Steeves, D. M., Kimball, B. R., & Peyghambarian, N. N. (2008). Time-resolved studies of photoinduced birefringence in azobenzene dye-doped polymer films. Applied optics, 47(28).
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  We measured transient photoinduced birefringence (delta n) in various azobenzene dye films by pumping with a nanosecond pulse at 532 nm and probing at 633 nm. The switch-on times for the photoinduced birefringence range from nanoseconds to milliseconds and are systematically related with the lowest optical transition energies for those films. Moreover, our results suggest that the transient photoinduced birefringence measurement is a convenient way to determine the relative energies of pi-pi(*) and n-pi(*) states in azo-based materials.
• Peyghambarian, N., Suzuki, S., Schülzgen, A., & Peyghambarian, N. N. (2008). Single-mode fiber laser based on core-cladding mode conversion. Optics letters, 33(4).
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  A single-mode fiber laser based on an intracavity core-cladding mode conversion is demonstrated. The fiber laser consists of an Er-doped active fiber and two fiber Bragg gratings. One Bragg grating is a core-cladding mode converter, and the other Bragg grating is a narrowband high reflector that selects the lasing wavelength. Coupling a single core mode and a single cladding mode by the grating mode converter, the laser operates as a hybrid single-mode laser. This approach for designing a laser cavity provides a much larger mode area than conventional large-mode-area step-index fibers.
• Peyghambarian, N., Tay, S., Blanche, P., Norwood, R., & Yamamoto, M. (2008). Rewritable holographic 3D displays. Optics and Photonics News, 19(7-8), 22-27.
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  Abstract: Researchers at the University of Arizona's College of Optical Sciences, US, and Nitto Denko Technical Corp., worked jointly, to create a rewritable holographic display that can enable 3D holographic film. Researchers demonstrated that holographic materials need to satisfy certain requirements, to be used for 3D rewritable 3D displays. These requirements, include high diffraction efficiency, high sensitivity, reversible recording, high spatial resolution, large area, fast recording, and long storage time. The rewritable 3D display features a total horizontal viewing angle of 45° and a vertical view zone of about 15°, with uniform brightness. It is observed that the hologram is viewable for up to three hours on the photorefractive sample, without the need for immediate projection tools, or magnification between the recorded image and the imager of the display.
• Peyghambarian, N., Tay, S., Blanche, P., Voorakaranam, R., Tunç, A. V., Lin, W., Rokutanda, S., Gu, T., Flores, D., Wang, P., Li, G., St Hilaire, P., Thomas, J., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. N. (2008). An updatable holographic three-dimensional display. Nature, 451(7179).
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  Holographic three-dimensional (3D) displays provide realistic images without the need for special eyewear, making them valuable tools for applications that require situational awareness, such as medical, industrial and military imaging. Currently commercially available holographic 3D displays use photopolymers that lack image-updating capability, resulting in restricted use and high cost. Photorefractive polymers are dynamic holographic recording materials that allow updating of images and have a wide range of applications, including optical correlation, imaging through scattering media and optical communication. To be suitable for 3D displays, photorefractive polymers need to have nearly 100% diffraction efficiency, fast writing time, hours of image persistence, rapid erasure, and large area-a combination of properties that has not been shown before. Here, we report an updatable holographic 3D display based on photorefractive polymers with such properties, capable of recording and displaying new images every few minutes. This is the largest photorefractive 3D display to date (4 x 4 inches in size); it can be recorded within a few minutes, viewed for several hours without the need for refreshing, and can be completely erased and updated with new images when desired.
• Peyghambarian, N., Zhu, X., Schülzgen, A., Li, H., Li, L., Han, L., Moloney, J. V., & Peyghambarian, N. N. (2008). Detailed investigation of self-imaging in large-core multimode optical fibers for application in fiber lasers and amplifiers. Optics express, 16(21).
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  Properties of the self-imaging effect based on multimode interference (MMI) in large-core passive optical fibers are investigated and analyzed in detail, with the purpose of using multimode active fibers for high power single-transverse-mode emission. Although perfect self-imaging of the input field from a standard single-mode fiber (SMF-28) in a multimode fiber becomes practically impossible as its core diameter is larger than 50 microm, a quasi-reproduction of the input field occurs when the phase difference between the excited modes and the peak mode inside the multimode fiber is very small. Our simulation and experimental results indicate that, if the length of the multimode fiber segment can be controlled accurately, reproduction of the input field with a self-imaging quality factor larger than 0.9 can be obtained. In this case, a low-loss hybrid fiber cavity composed of a SMF-28 segment and a very-large-core active multimode fiber segment can be built. It is also found that for the hybrid fiber cavity, increasing the mode-field diameter of the single-mode fiber improves both the self-imaging quality and the tolerance on the required length accuracy of the multimode fiber segment. Moreover, in this paper key parameters for the design of MMI-based fiber devices are defined and their corresponding values are provided for multimode fibers with core diameters of 50 microm and 105 microm.
• Peyghambarian, N., Zhu, X., Schülzgen, A., Li, H., Li, L., Wang, Q., Suzuki, S., Temyanko, V. L., Moloney, J. V., & Peyghambarian, N. N. (2008). Single-transverse-mode output from a fiber laser based on multimode interference. Optics letters, 33(9).
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  An alternative original approach to achieve single-transverse-mode laser emissions from multimode (MM) active fibers is demonstrated. The fiber cavity is constructed by simply splicing a conventional passive single-mode fiber (SMF-28) onto a few centimeters-long active MM fiber section whose length is precisely controlled. Owing to the self-imaging property of multimode interference (MMI) in the MM fiber, diffraction-limited laser output is obtained from the end of the SMF-28, and the MMI fiber laser is nearly as efficient as the corresponding MM fiber laser. Moreover, because of the spectral filtering effect during in-phase MMI, the bandwidth of the MMI fiber laser is below 0.5 nm.
• Schulzgen, A., Li, L. i., Zhu, X., Suzuki, S., Temyanko, V. L., Albert, J., & Peyghambarian, N. (2008). Microstructured soft glass fibers for advanced fiber lasers. Materials Research Society Symposium Proceedings, 1076, 65-73.
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  Abstract: Combining novel highly-doped phosphate glasses and advanced fiber drawing techniques, we fabricated and tested single-frequency fiber lasers that generate powers of more than 2 W. We demonstrate enhanced performance employing active photonic crystal fiber compared to more conventional devices that are based on large core step-index fiber. We also present results on phase-locking and coherently combining the output of up to 37 fiber cores into a single, near-Gaussian laser beam. To achieve exclusive oscillation of the fundamental in-phase supermode, several all-fiber laser cavities have been designed, numerically analyzed, fabricated, and tested. We will report on a 10 cm long monolithic all-fiber laser that emits more than 12 W of optical power and is based on combining the output of 19 active cores. All the cores are integrated within the same cladding and arranged in a two-dimensional isometric array. Our truly all-fiber approach that omits any free-space optical elements lead to a multi-emitter laser device that is free of optical alignment and robust against external perturbations. © 2008 Materials Research Society.
• Schülzgen, A., & Peyghambarian, N. (2008). Phosphate glass fibers advance fiber-laser capabilities. Laser Focus World, 44(10), 78-81.
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  Abstract: The development and introduction of phosphate glass fibers has significantly improved fiber-laser capabilities. Multicomponent phosphate glasses have emerged as better host materials for amplifiers and lasers, offering high solubility for rare-earth ions, better optical properties, and resistance against damage by high optical powers. There are many types of these phosphate glass fibers that can be selected to build an application-specific fiber laser. The availability of compatible fiber-laser components, such as fiber Bragg gratings (FBGs) need to be considered in the selection process, to retain the main fiber-laser advantage of a robust, all-fiber architecture. It is expected that host glass materials and dopants will enable fiber lasers to emit at a larger variety of wavelengths in future and widen their applications.
• Schülzgen, A., Li, L., Suzuki, S., Temyanko, V. L., Zhu, X., Jiang, S., Spiegelberg, C., Rogojan, R. M., Albert, J., & Peyghambarian, N. (2008). Recent advances in phosphate glass fiber and its application to compact high-power fiber lasers. Proceedings of SPIE - The International Society for Optical Engineering, 6873.
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  Abstract: Recent advances in the field of phosphate glass fiber lasers are reviewed. Fabrication of microstructured fiber and writing of fiber Bragg gratings in passive and active phosphate glass fiber are demonstrated. Based on these novel components we fabricate cm-long, Watt-level fiber lasers that allow for tunable, single longitudinal mode operation.
• Sehülzgen, A., Li, L., Nguyen, D., Spiegelberg, C., Rogojan, R. M., Laronche, A., Albert, J., & Peyghambarian, N. (2008). Distributed feedback fiber laser pumped by multimode laser diodes. Optics Letters, 33(6), 614-616.
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  PMID: 18347727;Abstract: A distributed feedback fiber laser made of highly Er-Yb codoped phosphate glass fiber has been demonstrated experimentally. Efficient pump absorption allows for multimode pumping into the cladding of the active fiber. Output powers up to 160 mW have been achieved. The 35 mm long fiber laser device emits with >50 dB side mode suppression ratio. © 2008 Optical Society of America.
• Suzuki, S., Schülzgen, A., & Peyghambarian, N. (2008). Single-mode fiber laser based on core-cladding mode conversion. Optics Letters, 33(4), 351-353.
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  PMID: 18278107;Abstract: A single-mode fiber laser based on an intracavity core-cladding mode conversion is demonstrated. The fiber laser consists of an Er-doped active fiber and two fiber Bragg gratings. One Bragg grating is a core-cladding mode converter, and the other Bragg grating is a narrowband high reflector that selects the lasing wavelength. Coupling a single core mode and a single cladding mode by the grating mode converter, the laser operates as a hybrid single-mode laser. This approach for designing a laser cavity provides a much larger mode area than conventional large-mode-area step-index fibers. © 2008 Optical Society of America.
• Tay, S., & Peyghambarian, N. (2008). Refreshable holographic 3-D displays. Information Display, 24(7), 16-20.
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  Abstract: Development of the photorefractive (PR) polymer devices combining the exceptional properties, such as large size, efficient recording, erasing capability, and persistent storage of holograms are highly satisfying the requirements to achieve updatable 3-D holographic displays with memory. Technical growth aspects of holography has already reflected successful implementations in static imaging, recording media used are write once, read-many types of the materials. The detailed study on the development comprises the main difference between the PR-polymer-based dynamic 3-D display and systems based on opto-electronic that is memory capability of the PR polymers. Dynamic of semi-dynamic (refreshable) materials have significantly improved the performance and extended the uses of holographic systems, especially enhanced the capabilities for 3-D displays. Holograms in the PR based 3-D displays show visibility within 45° viewing zone and persists for several hours without refreshing.
• Tay, S., Blanche, P. -., Voorakaranam, R., Tunç, A., Lin, W., Rokutanda, S., Gu, T., Flores, D., Wang, P., Li, G., Hilaire, P. S., Thomas, J., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. (2008). An updatable holographic three-dimensional display. Nature, 451(7179), 694-698.
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  PMID: 18256667;Abstract: Holographic three-dimensional (3D) displays provide realistic images without the need for special eyewear, making them valuable tools for applications that require situational awareness, such as medical, industrial and military imaging. Currently commercially available holographic 3D displays use photopolymers that lack image-updating capability, resulting in restricted use and high cost. Photorefractive polymers are dynamic holographic recording materials that allow updating of images and have a wide range of applications, including optical correlation, imaging through scattering media and optical communication. To be suitable for 3D displays, photorefractive polymers need to have nearly 100% diffraction efficiency, fast writing time, hours of image persistence, rapid erasure, and large area - a combination of properties that has not been shown before. Here, we report an updatable holographic 3D display based on photorefractive polymers with such properties, capable of recording and displaying new images every few minutes. This is the largest photorefractive 3D display to date (4 × 4 inches in size); it can be recorded within a few minutes, viewed for several hours without the need for refreshing, and can be completely erased and updated with new images when desired. ©2008 Nature Publishing Group.
• Tay, S., Thomas, J., Momeni, B., Askari, M., Hotchkiss, P. J., Jones, S. C., Marder, S. R., Adibi, A., Norwood, R. A., & Peyghambarian, N. (2008). Polymer nanocomposite infiltration of silicon photonic crystals. Proceedings of SPIE - The International Society for Optical Engineering, 6901.
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  Abstract: Infiltration of planar 2D silicon photonic crystals with nanocomposites using a simple melt processing technique is presented. The nanocomposites that were developed by evenly dispersing functionalized TiO2 nanoparticles into a photoconducting polymer exhibit high optical quality and tunable refractive index. The infiltrated photonic crystals show tuning of the photonic band-gap that is controllable by the adjustment of the nanoparticle loading level. These results may be useful in the development of tunable photonic devices, hybrid light emitting diodes and photovoltaics.
• Tay, S., Yamamoto, M., & Peyghambarian, N. (2008). Late-news invited paper: An updateable holographic 3-D display based on photorefractive polymers. Digest of Technical Papers - SID International Symposium, 39(1), 356-357.
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  Abstract: We present the first updateable holographic 3-D display with memory, capable of displaying a new image every few minutes. The holographic display uses a photorefractive polymer composite as recording medium with exceptional properties such as reversibility, high diffraction efficiency, large size (4×4 inches), fast recording and long hologram storage. © 2008 SID.
• Yamamoto, M., Lin, W., Gu, T., Flores, D., Wang, P., Tay, S., Blanche, P. -., Voorakaranam, R., Tunc, A. V., Li, G., Hilaire, P. S., Thomas, J., Norwood, R. A., & Peyghambarian, N. (2008). New photorefractive material development for new updatable holographic three-dimensional display. IDW '08 - Proceedings of the 15th International Display Workshops, 3, 1649-1652.
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  Abstract: We have successfully developed novel organic polymer-based photorefractive materials which have both good diffraction efficiency and long grating persistency. Developed materials were succeeded in principle-proving concept of novel, highly image-persistent, and rewritable holographic display systems. By using the materials, we are also aiming for developments of holographic rewritable display devices which require 3D visualization in application areas such as medical imaging, industrial CAD-CAM design, and security devices.
• Araci, I. E., Mendes, S. B., Yurt, N., Honkanen, S., & Peyghambarian, N. (2007). Highly sensitive spectroscopic detection of heme-protein submonolayer films by channel integrated optical waveguide. Optics Express, 15(9), 5595-5603.
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  PMID: 19532816;Abstract: A highly sensitive technique based on optical absorption using a single-mode, channel integrated optical waveguide is described for broad spectral band detection and analysis of heme-containing protein films at a glass/water interface. Fabrication steps and device characteristics of optical waveguides suitable for operation in the wavelength range of 400 - 650 nm are described. Experimental results reported here show a limit of detection smaller than 100 pg/cm2 for a submonolayer of ferricytochrome c by probing the Soret transition band with a 406-nm semiconductor diode laser propagating in a single-mode, ion-exchanged channel waveguide. By taking advantage of the exceptionally low limit of detection, we examined the adsorption isotherm of cytochrome c on a glass surface with unprecedented detail. Unlike other surface-specific techniques (e.g. SPR, integrated optic Mach-Zehnder interferometer) that probe local refractive-index changes and therefore are very susceptible to temperature fluctuations, the integrated optical waveguide absorption technique probes molecular-specific transition bands and is expected to be less vulnerable to environmental perturbations. © 2007 Optical Society of America.
• Enami, Y., DeRose, C. T., Loychik, C. L., Mathine, D. L., Norwood, R. A., Luo, J., Jen, A. K., & Peyghambarian, N. (2007). Improvement of electro-optic effect and novel waveguide structure in hybrid polymer/sol-gel modulators. Proceedings of SPIE - The International Society for Optical Engineering, 6470.
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  Abstract: A thermally stable crosslinkable electro-optic (EO) polymer is successfully contact-poled in a hybrid EO polymer/sol-gel waveguide modulator. The highest EO coefficient is demonstrated when the EO polymer is poled with a low resistivity sol-gel cladding layer. We achieve the highest in-device EO polymer r33 coefficient of 170pm/V at 1.55μm, which has not been possible with previously reported polymer claddings. A sol-gel waveguide/cladding plays the main role in our hybrid approach not only for poling efficiency, but also for low coupling loss, and stable coupling and waveguiding. The coupled light from the optical fiber propagates through the sol-gel input waveguide and adiabatically vertically transits between the sol-gel core and the EO polymer core. A phase modulator and a Mach-Zehnder modulator with a 2.4cm-long electrode and an inter-electrode distance of 15μm demonstrated a half wave voltages (Vπ) of 2.5V and 1.0V at 1.55μm, respectively. We also examine a push-pull poled Mach-Zehnder waveguide modulator.
• Enami, Y., DeRose, C. T., Loychik, C., Mathine, D., Norwood, R. A., Luo, J., Jen, A. K., & Peyghambarian, N. (2007). Erratum: Low half-wave voltage and high electro-optic effect in hybrid polymer/sol-gel waveguide modulators (Applied Physics Letters (2006) 89 (143506)). Applied Physics Letters, 91(1).
• Enami, Y., DeRose, C. T., Mathine, D., Loychik, C., Greenlee, C., Norwood, R. A., Stegeman, R., Kim, T. D., Luo, J., Tian, Y., Jen, A. K., & Peyghambarian, N. (2007). Ultrahigh electro-optic coefficient of 170pm/V and low V_π of 1V at 1.55μm in hybrid polymer/sol-gel waveguide modulators. Conference on Lasers and Electro-Optics, 2007, CLEO 2007.
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  Abstract: We demonstrated the highest electro-optic (EO) coefficient with the highest poling efficiency (∼100%) in actual modulator devices. This breakthrough was accomplished with contact poling of a crosslinkable EO polymer with an electrically conductive sol-gel cladding. © 2007 Optical Society of America.
• Enami, Y., Derose, C. T., Mathine, D., Loychik, C., Greenlee, C., Norwood, R. A., Kim, T. D., Luo, J., Tian, Y., Jen, A. K., & Peyghambarian, N. (2007). Erratum: Hybrid polymer/sol-gel waveguide modulations with exceptionally large electro-optic coefficients (Nature Photonics (2007) 1 (180-185)). Nature Photonics, 1(7), 423-.
• Enami, Y., Derose, C. T., Mathine, D., Loychik, C., Greenlee, C., Norwood, R. A., Kim, T. D., Luo, J., Tian, Y., Jen, A. K., & Peyghambarian, N. (2007). Hybrid polymersol-gel waveguide modulators with exceptionally large electro-optic coefficients. Nature Photonics, 1(3), 180-185.
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  Abstract: Electro-optic (EO) modulators are typically made from inorganic materials such as LiNbO3, but replacing them with organic EO materials, that is, ones with optical properties that change in response to an electric field, could be a promising alternative because they offer large bandwidth, ease of processing and relatively low cost. Here we incorporate a doped, crosslinked organic EO polymer into hybrid polymersol-gel waveguide modulator devices with exceptional performance. The half-wave voltages of the resulting Mach-Zehnder (MZ) and phase modulators at 1550nm are 1V and 2.5V, respectively. The unique properties of the sol-gel cladding materials used in the hybrid structure result in a 100 device poling efficiency, leading to respective in-device EO coefficients of 138pmV-1 and 170pmV-1 in the MZ and phase modulators. These results are the first to show in-device EO coefficients that are five to six times larger than those of the benchmark inorganic material. © 2007 Nature Publishing Group.
• Enami, Y., Mathine, D., Derose, C. T., Norwood, R. A., Luo, J., Jen, A. K., & Peyghambarian, N. (2007). Hybrid cross-linkable polymer/sol-gel waveguide modulators with 0.65 v half wave voltage at 1550 nm. Applied Physics Letters, 91(9).
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  Abstract: The authors report on a hybrid cross-linked electro-optic (EO) polymer/sol-gel Mach-Zehnder waveguide modulator with a half wave voltage (Vπ) of 0.65 V at 1550 nm. The low Vπ was achieved by a design that (1) combines both physical vertical tapers in the sol-gel core and photobleached index tapers in the EO polymer and (2) reduces the thickness of the device to 8 μm. These combined physical and index tapers result in improved optical mode confinement in the EO polymer with low adiabatic optical transition loss. The reduced thickness results in a larger field across the EO polymer for the same voltage, enabling a lower Vπ. © 2007 American Institute of Physics.
• Eralp, M., Thomas, J., Tay, S., Blanche, P. -., Schülzgen, A., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. (2007). Variation of Bragg condition in low-glass-transition photorefractive polymers when recorded in reflection geometry. Optics Express, 15(18), 11622-11628.
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  PMID: 19547522;Abstract: Two low-glass transition photorefractive polymer composites were investigated in a symmetric reflection geometry. The holograms recorded in 105 μm thick devices have reached diffraction efficiencies as high as 60%. Unlike the gratings recorded in transmission geometry, holograms recorded in reflection geometry showed high angular selectivity and the Bragg condition was observed to be sensitive to the magnitude of the external bias field. We attribute this effect to poling-induced birefringence and give a theoretical analysis to describe the observed results. © 2007 Optical Society of America.
• Goodnick, S., Korkin, A., Naito, T., Peyghambarian, N., & Chadha, M. (2007). Editorial for the special issue with publications of NGC2007 papers. Solid-State Electronics, 51(10 SPEC. ISS), 1251-.
• Guoqiang, L. i., Valley, P., Äyräs, P., Mathine, D. L., Honkanen, S., & Peyghambarian, N. (2007). High-efficiency switchable flat diffractive ophthalmic lens with three-layer electrode pattern and two-layer via structures. Applied Physics Letters, 90(11).
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  Abstract: A general design for switchable, flat, liquid crystal diffractive lens with three-layer electrode pattern and two-layer via structures is reported for near-, intermediate-, and distance-vision corrections of presbyopic eyes. The microfabricated transparent concentric ring electrodes are distributed in two layers and different voltages are applied to each electrode through bus lines in another layer. Connection between the electrodes and the bus lines is achieved by vias (conducting holes for vertical interconnections) in the third dimension. For demonstration, a lens is first tuned with a focal length of 1 m (1 diopter add power), eight-level phase modulation, and diffraction efficiency above 92% and then reconfigured to operate as a 2 diopter four-level lens with a diffraction efficiency of 78%. The lens operates with low voltages and a rise time of 150 ms. This design methodology allows the aperture needed for practical use and a power-failure-safe configuration. © 2007 American Institute of Physics.
• Leigh, M., Shi, W., Zong, J., Wang, J., Jiang, S., & Peyghambarian, N. (2007). Compact, single-frequency all-fiber Q-switched laser at 1 μm. Optics Letters, 32(8), 897-899.
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  PMID: 17375146;Abstract: We demonstrate a unique, all-fiber, actively Q-switched laser operating in the 1 μm region. The laser is compact, single mode, single frequency, highly polarized, and exhibits high peak power. The laser cavity is constructed without external coupling, utilizing fiber Bragg gratings that permit feedback at only a single polarization. By using a piezoelectric to press the fiber and modulate the fiber birefringence, the cavity is switched between high and low loss states, permitting Q-switching. We demonstrate this Q-switching at repetition rates up to 700 KHz. © 2007 Optical Society of America.
• Nguyen, D. T., Chavez-Pirson, A., Jiang, S., & Peyghambarian, N. (2007). A novel approach of modeling cladding-pumped highly Er-Yb Co-doped fiber amplifiers. IEEE Journal of Quantum Electronics, 43(11), 1018-1027.
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  Abstract: We present a new modeling method for claddingpumped highly Er-Yb co-doped fiber amplifiers. The method combines the beam propagation method (BPM) for the field propagation and nonlinear rate equations for the laser medium. The pump absorption, which is obtained numerically from the nonlinear rate equations, is used in BPM calculations of the field propagation. As a result, our method can effectively deal with difficult issues such as the multimode nature of cladding pumped schemes even in complicated structures, as well as strong nonlinearities in highly Er-Yb-doped fiber amplifiers. The simulation results are in very good agreement with experiments having different structures and different concentrations of Er-Yb. The method is particularly well suited to active fibers with low amplified spontaneous emission power, but it can also be developed further for more general cases. © 2007 IEEE.
• Peyghambarian, N., Eralp, M., Tay, S., Li, G., Thomas, J., Schülzgen, A., Marder, S. R., Yamamoto, M., & Norwood, R. A. (2007). Photorefractive polymers with superior performance. Nonlinear Optics Quantum Optics, 36(3-4), 309-318.
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  Abstract: We report on development of photorefractive materials with superior performance. High-voltage (5-10 kV) poling necessary for the operation of photorefractive polymeric devices has been a drawback of these materials. We have now developed devices that can be poled at order of magnitude lower voltages by carefully engineering the material composition using high performance nonlinear chromophores for thinner devices. For a thickness of 20 μm, the device showed more than 90% diffraction efficiency with a dominant fast response time of 27 ms at about an applied voltage of 1 kV. A useful diffraction efficiency of about 10% can be observed even at a voltage as little as 450 V, which demonstrates a major step forward in the possible applications of photorefractive devices. We have also been able to extend the operating wavelength to near IR. By employing a new sensitizer dye, we have demonstrated a first-time proof of photorefractivity at 975 nm in an all-organic composite with 90% diffraction efficiency and video rate response time using a low power cw laser. This is a significant advance in the development of all-organic PR device for near-infrared imaging and optical communication. Furthermore, devices were made to operate at 1550 nm wavelength, suitable for fiber optics applications. Using two-photon absorption (TPA) processes, we demonstrated more than 40% diffraction efficiency maintaining near video-rate response time. This approach provides the inherent advantage of non-destructive read-out using cw laser light. As an application of these devices, we demonstrated beam cleanup and aberration correction in a free space communication application. An oil-filled phase plate, which generates atmospheric-like wavefront aberrations, was employed and demonstrated high quality aberration corrections. © 2007 Old City Publishing, Inc.
• Rausch, K., Yurt, N., Geraghty, D. F., Eradat, N., Peyghambarian, N., & Kost, A. R. (2007). Broadband arrayed waveguide gratings on InP. Optical and Quantum Electronics, 39(7), 611-622.
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  Abstract: Broadband arrayed waveguide gratings on InP are presented using a novel S-shape design. This design was utilized to accommodate the large free spectral range required for broadband operation. Four and eight channel AWGs with a wavelength channel spacing of 18 nm are discussed. The output peaks of the AWGs have a wide FWHM of 11 nm which provides insensitive operation to polarization, temperature fluctuations, and chromatic dispersion. © 2007 Springer Science+Business Media, LLC.
• Suzuki, S., Jiang, S., Peyghambarian, N., & Chavez-Pirson, A. (2007). Image amplifier based on Yb³⁺-doped multi-core phosphate optical fiber. Optics Express, 15(7), 3759-3765.
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  PMID: 19532621;Abstract: We demonstrate image amplification with a 19-pixel optical image amplifier array based on high gain per unit length Yb3+-doped phosphate glass optical fiber. The 19 pixels of the image amplifier provide spatially uniform image amplification whose gain can reach 30 dB/pixel or more with a fiber length of 10 cm. This image amplifier responds quickly to changes in the image position - with potential for GHz-level frame rates. This unique approach for image amplification offers low noise, high gain, and wide field of view in a compact fiber-based device. © 2007 Optical Society of America.
• Tay, S., Thomas, J., Momeni, B., Askari, M., Adibi, A., Hotchkiss, P. J., Jones, S. C., Marder, S. R., Norwood, R. A., & Peyghambarian, N. (2007). Planar photonic crystals infiltrated with nanoparticle/polymer composites. Applied Physics Letters, 91(22).
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  Abstract: Infiltration of planar two-dimensional silicon photonic crystals with nanocomposites using a simple yet effective melt processing technique is presented. The nanocomposites that were developed by evenly dispersing functionalized Ti O2 nanoparticles into a photoconducting polymer were completely filled into photonic crystals with hole sizes ranging from 90 to 500 nm. The infiltrated devices show tuning of the photonic band gap that is controllable by the adjustment of the nanoparticle loading level. These results may be useful in the development of tunable photonic crystal based devices and hybrid light emitting diodes and solor cells. © 2007 American Institute of Physics.
• Voorst, P. V., Offerhaus, H. L., Wit, M. D., Tay, S., Thomas, J., Peyghambarian, N., & Boller, K. -. (2007). Injection locking of a broad area laser diode by use of holographic four-wave mixing in a photorefractive polymer. Conference on Lasers and Electro-Optics, 2007, CLEO 2007.
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  Abstract: We report on holographic injection locking using a novel photorefractive polymer introducing a new method to improve the beam quality of a broad area laser diode. © 2005 Optical Society of America.
• Voorst, P. V., Wit, M. D., Offerhaus, H. L., Tay, S., Thomas, J., Peyghambarian, N., & Boller, K. -. (2007). Holographic injection locking of a broad area laser diode via a photorefractive thin-film device. Optics Express, 15(26), 17587-17591.
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  PMID: 19551053;Abstract: We demonstrate locking of a high power broad area laser diode to a single frequency using holographic feedback from a photorefractive polymer thin-film device for the first time. A four-wave mixing setup is used to generate feedback for the broad area diode at the wavelength of the single frequency source (Ti: Sapphire laser) while the spatial distribution adapts to the preferred profile of the broad area diode. The result is an injection-locked broad area diode emitting with a linewidth comparable to the Ti: Sapphire laser. © 2007 Optical Society of America.
• Wang, P., Tao, G. u., Rokutanda, S., Yamamoto, M., Norwood, R., & Peyghambarian, N. (2007). Novel full-color photorefractive polymer for photonics applications. Conference on Lasers and Electro-Optics, 2007, CLEO 2007.
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  Abstract: Full-color sensitive (488nm, 532nm, 633nm) photorefractive polymer system based on hole-transport polytetraphenyldiaminobiphenyl (TPD) is present. Several novel dynamic holographic applications have been demonstrated based on these materials. © OSA.
• Wang, P., Tao, G. u., Rokutanda, S., Yamamoto, M., Norwood, R., & Peyghambarian, N. (2007). Novel full-color photorefractive polymer for photonics applications. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series.
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  Abstract: Full-color sensitive (488nm, 532nm, 633nm) photorefractive polymer system based on hole-transport polytetraphenyldiaminobiphenyl (TPD) is present. Several novel dynamic holographic applications have been demonstrated based on these materials. ©OSA.
• Yamashita, S., Yoshida, T., Set, S. Y., Polynkin, P., & Peyghambarian, N. (2007). Passively mode-locked short-cavity 10GHz Er:Yb-codoped phosphate-fiber laser using carbon nanotubes. Proceedings of SPIE - The International Society for Optical Engineering, 6453.
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  Abstract: Passively mode-locked fiber lasers are the best pulsed sources available today due to their simplicity and their ability to generate transform-limited pulses in the picosecond regimes. A drawback of the conventional passively mode-locked fiber lasers is that the pulse repetition rate is relatively low, at best a few tens of MHz, because of long cavity length. In order to raise repetition rate up to a few GHz, the cavity length has to be shortened below a few centimeters. Fiber lasers with such a short cavity require a high gain fiber and a small saturable absorber with low loss. Recently, the authors have proposed and demonstrated a small and low-loss saturable absorber device incorporating carbon nanotubes (CNT). Using CNT, we have realized very stable 2cm-long, 5GHz mode-locked Er:Yb-codoped silica-fiber laser, but the output power was limited to ∼0.2mW due to insufficient gain in the Er:Yb-codoped silica-fiber. Here we used heavily Er:Yb-codoped phosphate fiber to form 1 cm-long cavity with fiber mirrors, and succeeded in generating stable pulse trains with output power as high as 30mW and repetition rate as high as 10GHz at 1535nm.
• Albert, J., Schülzgen, A., Temyanko, V. L., Honkanen, S., & Peyghambarian, N. (2006). Strong Bragg gratings in phosphate glass single mode fiber. Applied Physics Letters, 89(10).
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  Abstract: Bragg gratings with reflectivities greater than 99% have been fabricated in phosphate glass single mode fibers by irradiating the fibers with 193 nm wavelength, high intensity pulses from an ArF excimer laser through a phase mask. Thermal treatment for 1000 h at temperatures up to 170°C did not degrade the gratings and resulted in an increase in grating strength. The refractive index modulation amplitudes obtained exceed 10-4. © 2006 American Institute of Physics.
• Auxier, J. M., Honkanen, S., Schülzgen, A., Morrell, M. M., Leigh, M. A., Sen, S., Borrelli, N. F., & Peyghambarian, N. (2006). Silver and potassium ion-exchanged waveguides in glasses doped with PbS semiconductor quantum dots. Journal of the Optical Society of America B: Optical Physics, 23(6), 1037-1045.
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  Abstract: We present a detailed analysis of potassium-sodium and silver-sodium ion-exchange processes for fabricating waveguides in glass doped with PbS semiconductor quantum dots. We compare the propagation losses of these waveguides, and we discuss the sources of these losses. In addition, we demonstrate a fourfold reduction in the propagation loss previously reported for potassium-sodium ion-exchanged waveguides and show that waveguides can be produced at additional quantum-dot resonances using both methods. We show that the near-infrared optical properties of these quantum dots remain intact by comparing the waveguide and bulk (unguided) luminescence spectra. Measurements of the near-field mode profiles show a high level of field confinement, which make these waveguides ideal for nonlinear optical (high-intensity) applications. © 2006 Optical Society of America.
• Enami, Y., DeRose, C. T., Loychik, C., Mathine, D., Norwood, R. A., Luo, J., Jen, A. K., & Peyghambarian, N. (2006). Low half-wave voltage and high electro-optic effect in hybrid polymer/sol-gel waveguide modulators. Applied Physics Letters, 89(14).
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  Abstract: The authors report on hybrid electro-optic (EO) polymer-sol-gel modulators with low half-wave voltage (Vπ) and low insertion loss. Larger EO coefficient r33 results from the high poling field achieved when EO polymer is sandwiched between sol-gel cladding layers. The reduced interelectrode distance (d) resulting from the elimination of the sol-gel core layer in the active region further reduces Vπ. Straight channel phase modulators operate with Vπ =4.2 V at 1550 nm using a reduced d of 11.5 μm, which corresponds to an r33 of 78 pmV, among the highest r33 reported. The authors also examine a Mach-Zehnder modulator with Vπ =3.9 V using a conventional d of 15 μm. © 2006 American Institute of Physics.
• Eralp, M., Thomas, J., Li, G., Tay, S., Schülzgen, A., Norwood, R. A., Peyghambarian, N., & Yamamoto, M. (2006). Photorefractive polymer device with video-rate response time operating at low voltages. Optics Letters, 31(10), 1408-1410.
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  PMID: 16642121;Abstract: The high-voltage bias required for video-rate compatible, efficient operation of a photorefractive polymer composite is reduced from 6-8 to 1.3 kV. At this low voltage, the device can hold erasable Bragg holograms with 80% efficiency in addition to having a video-rate response time. The transition of the hologram's state from thick to thin is analyzed in detail. © 2006 Optical Society of America.
• Eralp, M., Thomas, J., Tay, S., Guoqiang, L. i., Norwood, R., & Peyghambarian, N. (2006). Photorefractive polymer in reflection geometry with large efficiency. Proceedings of SPIE - The International Society for Optical Engineering, 6331.
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  Abstract: We have investigated photorefractive (PR) properties of a polymer composite with low glass-transition temperature (T g) in a symmetric reflection geometry. A diffraction efficiency of more than 30% is observed in 105μm thick devices. In low T g photorefractive polymers, poling of the nonlinear optical chromophores at room temperature leads to birefringence in the material. The birefringence will alter the Bragg condition, as the propagation vectors for object and reference beams as well as the readout angle are influenced We observed the Bragg-mismatch effect that caused a reduction in diffraction efficiency as the external field is increased. We have varied the angle of readout beam slightly at each bias field to get the highest efficiency.
• Eralp, M., Thomas, J., Tay, S., Li, G., Schülzgen, A., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. (2006). Submillisecond response of a photorefractive polymer under single nanosecond pulse exposure. Applied Physics Letters, 89(11).
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  Abstract: Individual nanosecond pulses at 532 nm are applied to record gratings in photorefractive composite. At 4 mJ/cm 2 illumination, maximum diffraction efficiencies of 56% have been reached with a build-up time of only 300 μs (t 1) demonstrating one order of magnitude faster recording compared to writing with continuous wave beams. This fast response enables applications in optical processing requiring frame rates of 100 Hz or more. Due to the short duration of the writing pulses, the recording is insensitive to vibrations. © 2006 American Institute of Physics.
• Guoqiang, L. i., Valley, P., Giridhar, M. S., Mathine, D. L., Meredith, G., Haddock, J. N., Kippelen, B., & Peyghambarian, N. (2006). Large-aperture switchable thin diffractive lens with interleaved electrode patterns. Applied Physics Letters, 89(14).
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  Abstract: The authors report on a high-performance large-aperture switchable diffractive lens using nematic liquid crystal that can be used as an adaptive eyewear. The odd- and even-numbered ring electrodes are separated in two layers, avoiding the gaps between the neighboring electrodes and allowing high diffraction efficiency. It is easier to avoid shorts between neighboring conductive electrodes and fabricate lenses with larger aperture and smaller feature size. With a four-level phase modulation, a 15 mm aperture, 2 dpt lens with small aberrations and diffraction efficiency of above 75% could be demonstrated with low operating voltages. The thickness of the liquid crystal is only 5 μm. The lens switching time is about 180 ms. The on and off states of the electrically controlled lens allows near and distance vision, respectively. The focusing power of the lens can be adjusted to be either positive or negative. This structure can be extended to higher-level phase modulation with even higher efficiencies. © 2006 American Institute of Physics.
• Guoqiang, L. i., Wang, P., Eralp, M., Thomas, J., Norwood, R. A., Yamamoto, M., & Peyghambarian, N. (2006). Efficient local fixing of photorefractive polymer hologram using a laser beam. Proceedings of SPIE - The International Society for Optical Engineering, 6314.
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  Abstract: We propose and demonstrate a novel technique for efficient local fixing of photorefractive polymer hologram using a laser beam. In the new technique, a CO 2 laser beam is used to heat the sample and a local hologram can be fixed easily. By using glass and sapphire with particular thickness as the substrates for the photorefractive device, the hologram can be fixed efficiently and at much faster speed. The fixation efficiency can be greater than 80% and the hologram can be fixed in a few seconds. This technique is critical for dynamic holographic 3D display and holographic data storage.
• Hoda, T., Äyräs, P., LaRussa, L., Peyghambarian, N., & Mathine, D. L. (2006). CMOS switched capacitor liquid crystal driver. Electronics Letters, 42(1), 1-2.
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  Abstract: A novel analogue drive circuit for a liquid crystal cell has been designed. The design was realised in a 0.5μm CMOS process and eight phase-locked channels with independent voltage control were developed. The channels were shown to produce over 5.6π optical phase shift using a ±2.5 V power supply. This drive circuit is proposed for use in portable battery operated applications where optical phase control is desired.
• Jianfeng, W. u., Jiang, S., Luo, T., Geng, J., Peyghambarian, N., & Barnes, N. P. (2006). Efficient thulium-doped 2-μm germanate fiber laser. IEEE Photonics Technology Letters, 18(2), 334-336.
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  Abstract: We report an efficient fiber laser operating near 2 μm. The glass for the fiber is germanate that is highly doped with thulium. The effect of cross relaxation energy transfer between thulium ions as observed from emission spectrum of the glass samples results in the laser having a very high slope efficiency of 58% with respect to launched power. This corresponds to a quantum efficiency of 1.79, indicating that each pump photon leads to near 1.8 excited Tm3+ ions. © 2005 IEEE.
• Norwood, R. A., Sumimura, H., Tay, S., Yamnitsky, K., Kropachev, A., Thomas, J., Peyghambarian, N., Moon, J. H., Shu, Y., & Skotheim, T. (2006). New organic infiltrants for 2-D and 3-D photonic crystals. Proceedings of SPIE - The International Society for Optical Engineering, 6331.
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  Abstract: Photonic crystals have now started to make the transition from basic to applied research, with new materials systems and device results being published on a frequent basis. While a number of photonic crystals have been made using organic materials, the lack of high index organic materials has impeded their development. We have investigated several novel high index organic systems for use in both 2-D and 3-D photonic crystals. 2-D photonic crystal templates were made by a rapid multibeam interference method in the photoresist SU-8, using 532nm laser radiation. These samples, typically on glass, were then infiltrated by a number of methods including from solution and melt, as well through chemical vapor deposition. Solutions of a titanium precursor with a cured refractive index of 2.1 at 633nm were infiltrated and cured in the SU-8 structure, with the infiltrant deposited by both by spin coating and casting. The resulting structure was shown to preserve the six-fold symmetry of the initial photonic crystal and subsequent firing at high temperature effectively removed the SU-8 template. We have also explored the infiltration of nanoamorphous carbon into the photonic crystals using chemical vapor deposition. This material, which is essentially a carbon-silicon ceramic, has exceptional infrared optical properties with a refractive index > 2 for wavelengths beyond 2 μm. The SU-8 polymer template has been shown to survive the CVD deposition process and the resulting infiltrated structure also preserves the initial PC symmetry. A series of metal-like PCs with a full range of properties is enabled by the ability to dope the nanoamorphous carbon with metals that possess exceptional refractive indices in the infrared regions of interest. We have also investigated the potential for nonlinear optical devices based upon azobenzene copolymer infiltrated silicon PCs and demonstrate the excellent properties of this material with respect to all-optical effects.
• Peyghambarian, N., Dalton, L., Alex, J., Kippelen, B., Marder, S., Norwood, R., & Perry, J. W. (2006). Technological advances brighten horizons for organic nonlinear optics. Laser Focus World, 42(8), 85-92.
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  Abstract: The technological advances in organic nonlinear optical (NLO) materials, including materials with exceptional electro-optic, two-photon-absorption, and third-harmonic generation (THG) properties having supramolecular assemblies, are discussed. These assemblies are prepared using chromophoric building blocks with optimized molecular properties. The nonlinear optical materials are used in electro-optic (EO) modulators with low operating voltage and low insertion loss, in ultrashort-pulse diagnostic applications, and in imaging applications. The THG signals helps to demonstrate interferometric autocorrelation for the characterization of short pulses with a standard nonamplified silicon detector, and frequency-resolved optical gating (FROG) with a portable fiber spectrometer. These new materials also enables the demonstration of real-time, time-gated, direct imaging through scattering media using THG in the eye-safe and telecommunication compatible near-infrared spectral region.
• Peyghambarian, N., Li, G., Mathine, D. L., Valley, P., Ayräs, P., Haddock, J. N., Giridhar, M. S., Williby, G., Schwiegerling, J., Meredith, G. R., Kippelen, B., Honkanen, S., & Peyghambarian, N. N. (2006). Switchable electro-optic diffractive lens with high efficiency for ophthalmic applications. Proceedings of the National Academy of Sciences of the United States of America, 103(16).
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  Presbyopia is an age-related loss of accommodation of the human eye that manifests itself as inability to shift focus from distant to near objects. Assuming no refractive error, presbyopes have clear vision of distant objects; they require reading glasses for viewing near objects. Area-divided bifocal lenses are one example of a treatment for this problem. However, the field of view is limited in such eyeglasses, requiring the user to gaze down to accomplish near-vision tasks and in some cases causing dizziness and discomfort. Here, we report on previously undescribed switchable, flat, liquid-crystal diffractive lenses that can adaptively change their focusing power. The operation of these spectacle lenses is based on electrical control of the refractive index of a 5-mum-thick layer of nematic liquid crystal using a circular array of photolithographically defined transparent electrodes. It operates with high transmission, low voltage (
• Peyghambarian, N., Schülzgen, A., Li, L., Temyanko, V. L., Suzuki, S., Moloney, J. V., & Peyghambarian, N. N. (2006). Single-frequency fiber oscillator with watt-level output power using photonic crystal phosphate glass fiber. Optics express, 14(16).
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  Utilizing phosphate glass fiber with photonic crystal cladding and highly doped, large area core a cladding-pumped, single-frequency fiber oscillator is demonstrated. The fiber oscillator contains only 3.8 cm of active fiber in a linear cavity and operates in the 1.5 micron region. Spectrally broad, multimode pump light from semiconductor laser diodes is converted into a single-mode, single-frequency light beam with an efficiency of about 12% and the oscillator output power reached 2.3 W.
• Schúlzgen, A., Auxier, J. M., Honkanen, S., Li, L., Temyanko, V. L., Chen, S. -., Suzuki, S., Morrell, M. M., Sabet, S., Sen, S., Borrelli, N. F., & Peyghambarian, N. (2006). Active micro- and nano-structured glass fiber and waveguide devices. Proceedings of SPIE - The International Society for Optical Engineering, 6183.
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  Abstract: Otical and electron confinement are utilized to tailor the optical characteristics of active materials and photonic devices. A technique to incorporate semiconductor quantum dots into planar glass waveguides with low propagation loss is demonstrated. The waveguides are fabricated by potassium-sodium and silver-sodium ion exchange processes in glasses that contain PbS quantum dots with radii of a few nanometers. The unique optical properties of the quantum dots are preserved throughout the waveguide fabrication process. We also demonstrate novel compact fiber lasers based on active, highly doped fibers with photonic crystal cladding. The flexibility provided by microstructuring the fiber enables improved fiber laser performance and several Watts of laser output are generated from few centimeters of active fiber.
• Thomas, J., Eralp, M., Tay, S., Guoqiang, L., Peng, W., Yamamoto, M., Schülzgen, A., Norwood, R., & Peyghambarian, N. (2006). Photorefractive polymers with sub-millisecond response time. Proceedings of SPIE - The International Society for Optical Engineering, 6335.
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  Abstract: We report the photorefractive properties of tetraphenyldiaminobiphenyl (TPD) based polymer composites that have been developed for single pulse laser operation at 532 nm. With an optimized composite, we demonstrate more than 50% diffraction efficiency using 4 mJ/cm 2 single shot writing and 633 nm continuous wave (cw) beam reading. The present devices showed a 300 μs fast response time. This reveals the potential for these polymer devices in applications which require fast writing and erasure. Since the writing pulse-width is in nanosecond time scale, the recording is totally insensitive to vibrations. These devices can also be used as a stepping stone to realize all-color holography since they are sensitive to both green (532nm) and red (633nm) wavelengths. The holograms can be written with either of these two wavelengths and can be read by the same wavelength or the other wavelength with high diffraction efficiency. This demonstrates that these devices have the advantage of performing two-color holography, a step closer to a dynamic full-color holographic recording medium.
• Araci, I. E., Vorbeck, S., Schneiders, M., Ansari, M. J., Peyghambarian, N., & Kueppers, F. (2005). System optimization and significant reach extension using alternating dispersion compensation for 160 Gbit/s transmission links. Optics Express, 13(17), 6336-6344.
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  PMID: 19498647;Abstract: Dispersion post compensated 160 Gbit/s transmission systems are optimized for a wide range of transmission fiber and DCF input powers. The simulation results for SMF, NZDSFHD, NZDSFLD fiber types and for NRZ, RZ, CSRZ and CSRZ-DPSK modulation formats are presented. CSRZ-DPSK modulation, balanced receiver (Bal-Rx) and NZDSFHD transmission fiber combination found to be superior to others, giving 880 km system reach with Q > 6. The alternating dispersion compensation is then applied and optimized for various modulation format and fiber types. This simple dispersion management technique provided significant system reach extension of 60% when CSRZ-DPSK modulation, Bal-Rx and SMF transmission fiber combination is used. © 2005 Optical Society of America.
• Araci, I. E., Yurt, N., Honkanen, S., Mendes, S. B., & Peyghambarian, N. (2005). Hybrid glass and sol-gel integrated optical waveguides for absorption-based biosensing. Proceedings of SPIE - The International Society for Optical Engineering, 6004.
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  Abstract: A novel integrated optical planar waveguide platform for absorption-based biosensing is demonstrated. The platform integrates surface ion-exchanged channel waveguides with one-step UV patterned sol-gel structures to define the probing regions. Cytochrome c protein was utilized to characterize the device performance. Spectroscopically specific attenuation of approximately 2 dB in the guided signal occurred at 532nm for 1.4 cm long probing region. The estimated level of detection is about 1 pmol/cm 2 of surface adsorbed cytochrome c. The proposed structure enables environmentally stable, compact, and inexpensive sensing devices that can be applied to a wide range of biological and chemical species.
• Auxier, J. M., Schülzgen, A., Morrell, M. M., West, B. R., Honkanen, S., Sen, S., Borrelli, N. F., & Peyghambarian, N. (2005). Quantum dots for fiber laser sources. Proceedings of SPIE - The International Society for Optical Engineering, 5709, 249-262.
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  Abstract: In this invited paper, we will discuss the use of quantum dots as nonlinear optical elements in fiber laser sources. Furthermore, a review of the fabrication of the first low-loss (< 0.5 dB/cm) ion-exchanged waveguides in a quantum-dot-doped glass will be presented. We will discuss the coupling, propagation, absorption, and scattering losses in these waveguides. The near-field mode profile along with the refractive index profile of these waveguides will be presented. This PbS quantum-dot-doped glass was chosen due to its attractive optical gain and bleaching characteristics at wavelengths throughout the near infrared. This bleaching of the ground-state optical transition has been utilized for passive modelocking of a variety of lasers in the near infrared. In addition, we will discuss some of the potential integrated and fiber optics applications of our quantum-dot-doped waveguides.
• Guoqiang, L. i., Eralp, M., Thomas, J., Tay, S., Schülzgen, A., Norwood, R. A., & Peyghambarian, N. (2005). All-optical dynamic correction of distorted communication signals using a photorefractive polymeric hologram. Applied Physics Letters, 86(16), 1-3.
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  Abstract: All-optical real-time dynamic correction of wave front aberrations for image transmission is demonstrated using a photorefractive polymeric hologram. The material shows video rate response time with a low power laser. High-fidelity, high-contrast images can be reconstructed when the oil-filled phase plate generating atmospheric-like wave front aberrations is moved at 0.3 mms. The architecture based on four-wave mixing has potential application in free-space optical communication, remote sensing, and dynamic tracking. The system offers a cost-effective alternative to closed-loop adaptive optics systems. © 2005 American Institute of Physics.
• Inada, Y., Hara, Y., Mukaiyama, T., Peng, X., Jiang, S., Peyghambarian, N., & Kuwata-Gonokami, M. (2005). Resonant emission mode identification by angle tuned prism coupling in Er³⁺ doped tellurite glass microsphere. Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest, 2005, 364-365.
• Jianfeng, W. u., Jiang, S., & Peyghambarian, N. (2005). 1.5-μm-band thulium-doped microsphere laser originating from self-terminating transition. Optics Express, 13(25), 10129-10133.
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  PMID: 19503227;Abstract: Continuous-wave 1.5-μm-band laser is demonstrated in thulium doped tellurite glass microsphere by single laser pumping. 1.9-μm laser from the lower transition (3F4->3H6) of Tm3+ is generated to depopulate the lower level (3F 4) of 1.5-μm transition (3H 4->3F4) in order to achieve the population inversion. Laser wavelength of 3H4->3F 4 transition is shifted by 30 nm from the emission peak. Slope efficiency of 1.9-μm laser is improved after the 1.5-μm laser starts to lase. © 2003 Optical Society of America.
• Jianfeng, W. u., Jiang, S., Qiu, T., Morrell, M., Schulzgen, A., & Peyghambarian, N. (2005). Cross-relaxation energy transfer in Tm ³⁺ doped tellurite glass. Proceedings of SPIE - The International Society for Optical Engineering, 5723, 152-161.
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  Abstract: A self-calibrating fluorescence spectroscopy technique was applied to study cross-relaxation 3H 4, 3H 6 → 3F 4, 3F 4, and energy migration 3H 4, 3H 6 → 3F 4, 3F 4, of the Tm 3+ Ions doped in the tellurite glass. These glasses are investigated for their use in realization of 2 micron fiber lasers. Micro and macro-parameters of the energy transfer and migration were calculated by the means of the model of phonon-assistant multi-polar interaction and hoping mode. Steady rate equation analysis was used to fit the experimental fluorescence ratio of samples with different concentrations. We found that high-order (dipole-quadrupole) interaction was the dominant mechanism in the energy transfer of Thulium ions.
• Jianfeng, W. u., Jiang, S., Qiu, T., Morrell, M., Schulzgen, A., & Peyghambarian, N. (2005). Tm ³⁺ doped tellurite glass microsphere laser. Proceedings of SPIE - The International Society for Optical Engineering, 5723, 21-27.
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  Abstract: Wavelength of 2000 nm single mode microsphere laser from highly thulium doped tellurite glass microsphere was demonstrated by means of fiber taper coupling. Laser wavelength was red shift from the emission peak of thulium ions at 1800 nm.
• Jianfeng, W. u., Jiang, S., Qua, T., Kuwata-Gonokami, M., & Peyghambarian, N. (2005). 2 μm lasing from highly thulium doped tellurite glass microsphere. Applied Physics Letters, 87(21), 1-3.
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  Abstract: A single mode microsphere laser at 2 μm is demonstrated from a highly thulium doped tellurite glass microsphere. Glass samples with various doping concentrations are fabricated and characterized to choose the material with the highest pump efficiency. The laser wavelength is redshifted from the emission peak of thulium ions at 1800 nm due to the different mode distribution inside the microsphere. The laser line width (full width at half maximum) is measured as 115 MHz. © 2005 American Institute of Physics.
• Peng, X., Song, F., Kuwata-Gonokami, M., Jiang, S., & Peyghambarian, N. (2005). Er³⁺-doped tellurite glass microsphere laser: Optical properties, coupling scheme, and lasing characteristics. Optical Engineering, 44(3), 1-8.
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  Abstract: We present a comprehensive review of work on the Er3+-doped tellurite glass microsphere laser. We discuss the optical properties of Er3+-doped tellurite glass, including the emission cross section, the absorption cross section, and the lifetime analysis. Whispering-gallery modes in microspheres and fiber-taper coupling schemes are described, and theoretical analysis is performed for optimization. Finally, lasing characteristics such as the threshold, the lasing wavelength, and the temperature dependence of the microsphere laser are analyzed. Microsphere lasers with different Er2 O3 doping concentrations have been fabricated and examined. A state-of-the-art L-band microsphere laser with 124.5-μW maximum output power is demonstrated. These miniature microsphere lasers have great potential and have attracted considerable attention because of their versatility for signal processing, fiber communication, and photon computation, as well as laser stabilization and sensing applications. © 2005 Society of Photo-Optical Instrumentation Engineers.
• Peyghambarian, N., & Norwood, R. A. (2005). Organic optoelectronics. Optics and Photonics News, 16(2), 30-35.
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  Abstract: The benefits of organic and polymeric materials used for various applications in optical communications are discussed. The ultraviolet cured systems of highly cross-linked low Tg optical polymers eliminates the need for costly dry etching processes and also lowers the stress in the waveguide. Low-loss polymers also reduces electrical power consumption for devices. It is concluded that the levels of loss achieved by both halogenated cross-linked and conventional perfluoropolymer systems makes it suitable for high levels of optical integration.
• Peyghambarian, N., & Norwood, R. A. (2005). Organic optoelectronocis: Materials and devices for photonic applications, part II. Optics and Photonics News, 16(4), 28-33.
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  Abstract: The state-of-art in organic solar cells, organic light emitting diode (OLED) technology for flexible displays and organic optical data storage is discussed. Organic heterojunction solar cells are very similar in construction to OLEDs, in that they typically consist of a glass substrate, an indium tin oxide (ITO) transparent conducting electrode, a hole transport layer, an electron transport layer and a top metal electrode. Organic thin film transistor (OTFT) could be used with OLED technology to produce inexpensive, flexible displays. Sarnoff Laboratories, developed a video-rate capable of flexible OLED display which highlighted the unique advantages of organic optoelectronics.
• Peyghambarian, N., & Schülzgen, A. (2005). Fiber lasers: High-power devices in compact packages. Optics and Photonics News, 16(6), 36-41.
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  Abstract: Fiber lasers, which can deliver large amounts of energy to a target in a very precise but flexible way, are discussed. Fiber lasers use guided-mode propagation to create extremely robust laser structures with resonator lengths that can reach hundreds of meters. Fiber lasers can operate at a multitude of wavelengths, and the availability of different pump wavelengths can be exploited. The laser cavity of fiber lasers is extremely simple and robust, which leads to exceptional reliability and minimum maintenance and ownership cost.
• Peyghambarian, N., Li, L., Schülzgen, A., Temyanko, V. L., Li, H., Sabet, S., Morrell, M. M., Mafi, A., Moloney, J. V., & Peyghambarian, N. N. (2005). Investigation of modal properties of microstructured optical fibers with large depressed-index cores. Optics letters, 30(24).
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  We present what is, to the best of our knowledge, the first systematic study on how negative core-cladding index difference influences microstructured optical fiber's modal behavior. Single-mode lasing has been realized for short-length cladding-pumped phosphate glass microstructured fibers with large depressed-index Er(3+)-Yb(3+)-codoped cores.
• Peyghambarian, N., Li, L., Schülzgen, A., Temyanko, V. L., Qiu, T., Morrell, M. M., Wang, Q., Mafi, A., Moloney, J. V., & Peyghambarian, N. N. (2005). Short-length microstructured phosphate glass fiber lasers with large mode areas. Optics letters, 30(10).
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  We report fabrication and testing of the first phosphate glass microstructured fiber lasers with large Er-Yb-codoped cores. For an 11-cm-long cladding-pumped fiber laser, more than 3 W of continuous wave output power is demonstrated, and near single-mode beam quality is obtained for an active core area larger than 400 microm2.
• Peyghambarian, N., Polynkin, A., Polynkin, P., Schülzgen, A., Mansuripur, M., & Peyghambarian, N. N. (2005). Watts-level, short all-fiber laser at 1.5 microm with a large core and diffraction-limited output via intracavity spatial-mode filtering. Optics letters, 30(4).
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  We report over 2 W of single spatial-mode output power at 1.5 microm from an 8-cm-long, large-core phosphate fiber laser. The fiber has a numerical aperture of approximately equal to 0.17 and a 25-microm-wide core, heavily doped with 1% Er(+3) and 8% Yb(+3). The laser utilizes a scalable evanescent-field-based pumping scheme and can be pumped by as many as eight individual multimode pigtailed diode laser sources at a wavelength of 975 nm. Nearly diffraction-limited laser output with a beam quality factor M2 approximately equal to 1.1 is achieved by use of a simple intracavity all-fiber spatial-mode filter. Both spectrally broadband and narrowband operation of the laser are demonstrated.
• Peyghambarian, N., Polynkin, P., Polynkin, A., Mansuripur, M., Moloney, J., & Peyghambarian, N. N. (2005). Single-frequency laser oscillator with watts-level output power at 1.5 microm by use of a twisted-mode technique. Optics letters, 30(20).
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  We report an all-fiber laser oscillator producing as much as 1.9 W of single-frequency direct output at 1.5 microm. Spatial gain hole burning in the active fiber has been eliminated by use of a twisted-mode cavity approach. The two short pieces of a polarization-maintaining fiber that were spliced to the ends of the active fiber served as ultracompact quarter-wave plates. To our knowledge, the use of such a wave plate to manipulate the polarization state of light inside a fiber laser cavity is reported here for the first time. The laser output is linearly polarized and delivered through a polarization-maintaining fiber pigtail. We believe that the output power of our laser is the highest among all single-frequency fiber laser oscillators reported to date.
• Peyghambarian, N., Qiu, T., Suzuki, S., Schülzgen, A., Li, L., Polynkin, A., Temyanko, V., Moloney, J. V., & Peyghambarian, N. N. (2005). Generation of watt-level single-longitudinal-mode output from cladding-pumped short fiber lasers. Optics letters, 30(20).
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  We generate as much as 1.6 W of continuous-wave 1550 nm single-longitudinal-mode output from a cladding pumped Er-Yb codoped phosphate fiber laser. This power is to our knowledge among the highest in single-longitudinal-mode fiber lasers. The narrowband fiber Bragg grating output coupler is demonstrated to be an effective element for providing the single-longitudinal-mode selection.
• Reinke, C. M., Jafarpour, A., Huang, J., Soltani, M., Momeni, B., Adibi, A., Norwood, R., & Peyghambarian, N. (2005). Integrable planar photonic crystal devices in silicon using nonlinear effects. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 2005, 212-213.
• Seneschal, K., Smektala, F., Bureau, B., Floch, M. L., Jiang, S., Luo, T., Lucas, J., & Peyghambarian, N. (2005). Properties and structure of high erbium doped phosphate glass for short optical fibers amplifiers. Materials Research Bulletin, 40(9), 1433-1442.
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  Abstract: New phosphate glasses have been developed in order to incorporate high rare-earth ions concentrations. These glasses present a great chemical stability and a high optical quality. The phosphate glass network is open, very flexible, with a linkage of the tetrahedrons very disordered and contains a larger number of non-bridging oxygens (66%). The great stability and resistance against crystallization associated with the possibility to incorporate high doping concentration of rare-earth ions in these phosphate glasses make them very good candidates for the realization of ultra short single mode amplifiers with a high gain at 1.55 μm. © 2005 Elsevier Ltd. All rights reserved.
• Sun, X., Peyghambarian, N., Kost, A. R., & Eradat, N. (2005). Large blueshift of the band gap of GaAsSbAlSb quantum wells with ion implantation. Applied Physics Letters, 86(1), 011905-1-011905-3.
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  Abstract: We describe studies of intermixing in GaAsSbAlSb quantum wells with 18.8% and 31% arsenic, grown on GaSb substrates. Samples were implanted with a 1× 1013 cm-2 dose of 330 keV boron ions and annealed. The band gap for the samples was determined from photoluminescence. The maximum blueshift of the band gap was 141 nm (86 meV) for the quantum wells with 18.8% arsenic and 198 nm (124 meV) for the quantum wells with 31% arsenic. The blueshifts are attributed to interdiffusion of both group-III and group-V constituents. Photoluminescence strength generally increased with annealing temperature. © 2005 American Institute of Physics.
• Tay, S., Thomas, J., Eralp, M., Guoqiang, L. i., Norwood, R. A., Schülzgen, A., Yamamoto, M., Barlow, S., Walker, G. A., Marder, S. R., & Peyghambarian, N. (2005). High-performance photorefractive polymer operating at 1550 nm with near-video-rate response time. Applied Physics Letters, 87(17), 1-3.
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  Abstract: The development of a high-performance photorefractive polymer composite operating at 1550 nm is reported. We show 40% internal diffraction efficiency with response time of 35 ms and a net gain of 20 cm-1 in four-wave mixing and two-beam coupling experiments, respectively. This is more than an order of magnitude improvement in the diffraction efficiency and net two beam coupling gain and two orders of magnitude in the response time than the previously reported photorefractive polymer operating at this technologically important wavelength. The improvement in photorefractive characteristics is accomplished by an enhanced orientation of the nonlinear optical chromophore in the present composite. © 2005 American Institute of Physics.
• Thomas, J., Eralp, M., Tay, S., Guoqiang, L. i., Yamamoto, M., Norwood, R., Marder, S. R., & Peyghambarian, N. (2005). Photorefractive polymers with superior performance. Optics and Photonics News, 16(12 SPEC. ISS.), 31-.
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  Abstract: The advantages of devices used for reducing the applied poling voltage required in photorefractive polymers is described. Photorefractive materials are used in applications in beam-cleanup and amplification, real-time image processing, optical phase conjugation, pattern recognition, 3D displays and novelty filters. The use of two-photon absorption (TPA) processes improves the diffraction efficiency to 40 percent and maintain near-video-rate response time. The devices provide the advantage of nondestructive readout with cw laser light and also increases the operating wavelength.
• Yurt, N., Mune, K., Naito, R., Fukuoka, T., Mochizuki, A., Matsumoto, K., Meredith, G., Peyghambarian, N., & Jabbour, G. E. (2005). Fabrication and characterization of low-loss optical waveguides using a novel photosensitive polyimide. Journal of Lightwave Technology, 23(3), 1291-1294.
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  Abstract: This paper presents simple fabrication of optical waveguides using a novel photosensitive polyimide (PSPI). PSPI has a glass transition temperature (Tg) of 330 °C and is directly patterned by ultraviolet (UV) exposure and wet-chemical development, lending itself to low-cost fabrication techniques. The fabricated waveguides possess low optical absorption at 1.3 and 1.5 μm. Single and multimode buried ridge waveguides were made and tested, and a 0.4-dB/cm optical propagation loss is measured at 1.55 μm. © 2005 IEEE.
• Yurt, N., Rausch, K., Kost, A. R., & Peyghambarian, N. (2005). Design and fabrication of a broadband polarization and temperature insensitive arrayed waveguide grating on InP. Optics Express, 13(14), 5535-5541.
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  PMID: 19498550;Abstract: An arrayed waveguide grating (AWG) with a novel S-shaped design for broadband operation is demonstrated for the first time with III-V semiconductors. This device design provided a polarization and temperature insensitive operation. It is also shown that, despite the wide operating range, chromatic dispersion does not degrade the performance of the AWG. The AWG is operational above the absorption edge of the semiconductor (1100nm) and can function for a wide range of wavelengths covering the coarse wavelength multiplexing range from 1270nm to 1610nm. A four channel AWG with this novel design was fabricated and characterized. ©2005 Optical Society of America.
• Auxier, J. M., Morrell, M. M., West, B. R., Honkanen, S., Schülzgen, A., Peyghambarian, N., Sen, S., & Borrelli, N. F. (2004). Ion-exchanged waveguides in glass doped with PbS quantum dots. Applied Physics Letters, 85(25), 6098-6100.
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  Abstract: The lowest-loss (≲1 dBcm) ion-exchanged waveguides in glass doped with PbS quantum dots are presented. Near-field mode profile and refractive index profile using the refracted near-field technique were measured for these waveguides. We demonstrate that the optical properties of this glass remain unchanged during the ion-exchange process. © 2004 American Institute of Physics.
• Auxier, J. M., West, B. R., Honkanen, S., Schülzgen, A., Peyghambarian, N., Sen, S., & Borrelli, N. F. (2004). Quantum-dot-doped waveguides produced by ion exchange. OSA Trends in Optics and Photonics Series, 96 A, 555-556.
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  Abstract: We present the first low-loss (< 0.5 dB/cm) ion-exchanged waveguides in glass doped with lead-salt quantum dots. Measurements of the waveguides' coupling losses, near-field mode profile, and index profile are presented. © 2003 Optical Society of America.
• Chavez-Pirson, A., Tian, W., Nguyen, D., Luo, T., Steward, B., Paysnoe, G., Jiang, S., & Peyghambarian, N. (2004). Multimode-pumped monolithic amplifier arrays based in erbium-doped phosphate glass. OSA Trends in Optics and Photonics Series, 96 A, 949-951.
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  Abstract: We demonstrate a monolithic optical amplifier array based on high gain per unit length erbium-doped phosphate glass. Two cores from one 8-cm long chip are cascaded to deliver 22-dB internal gain across the C-band. © 2003 Optical Society of America.
• Enami, Y., Jen, A. K., Meredith, G., & Peyghambarian, N. (2004). Hybrid electro-optic polymer/sol-gel waveguide modulators fabricated by all-wet etching process, using straight channel and Mach-Zehnder waveguides. Proceedings of SPIE - The International Society for Optical Engineering, 5350, 89-96.
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  Abstract: We report hybrid electro-optic (EO) polymer/sol-gel waveguide modulators with a structure for an EO polymer confined laterally in a sol-gel over cladding, which is fabricated by all-wet etching process. The structure enables an adiabatic transition between the sol-gel waveguide and thick EO polymer overlayer. Intensity mode is confined well in 0.9-μm-thick EO polymer overlayer, which reduces a half wave voltage (V π) due to increased overlap integral in the hybrid EO modulator. Straight channel birefringence EO modulators with the structure reduce the V π by the factor of 4 after guided wave well confined in the EO polymer. The straight channel waveguide modulator with 2.4-cm-long electrode demonstrated the V π of 13 V. Preliminary testing results using a Mach-Zehnder waveguide modulator were investigated to reduce the V π further.
• Enami, Y., Jen, A. K., Meredith, G., & Peyghambarian, N. (2004). Hybrid electro-optic polymer/sol-gel waveguide modulators fabricated by all-wet etching process, using straight channel and Mach-Zehnder waveguides. Proceedings of SPIE - The International Society for Optical Engineering, 5351, 28-35.
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  Abstract: We report hybrid electro-optic (EO) polymer/sol-gel waveguide modulators with a structure for an EO polymer confined laterally in a sol-gel over cladding, which is fabricated by all-wet etching process. The structure enables an adiabatic transition between the sol-gel waveguide and thick EO polymer overlayer. Intensity mode is confined well in 0.9-μm-thick EO polymer overlayer, which reduces a half wave voltage (V π) due to increased overlap integral in the hybrid EO modulator. Straight channel birefringence EO modulators with the structure reduce the V π by the factor of 4 after guided wave well confined in the EO polymer. The straight channel waveguide modulator with 2.4-cm-long electrode demonstrated the V π of 13 V. Preliminary testing results using a Mach-Zehnder waveguide modulator were investigated to reduce the V π further.
• Eralp, M., Thomas, J., Tay, S., Guoqiang, L. i., Meredith, G., Schülzgen, A., Peyghambarian, N., Walker, G. A., Barlow, S., & Marder, S. R. (2004). High-performance photorefractive polymer operating at 975 nm. Applied Physics Letters, 85(7), 1095-1097.
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  Abstract: A family of photorefractive polymer composites that enable high-performance device operation at a wavelength of 975 nm were analyzed. It was observed that the gratings of photorefractive polymer could be written within ten milliseconds. It was also observed that the diffraction efficiency from these gratings reached 60% and there was a two-beam coupling gain of 130 cm -1. It was found that there was a possibility of achieving faster response times within this family of polymer composites.
• Fuentes-Hernandez, C., Thomas, J., Meredith, G., Peyghambarian, N., Marder, S. R., & Kippelen, B. (2004). Trapping mechanisms and dynamics in bis-triarylamine based photorefractive polymer composites. Proceedings of SPIE - The International Society for Optical Engineering, 5521, 96-102.
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  Abstract: We report on the trapping mechanisms in bis-triarylamine (PATPD) based polymer composites. Although exceptional stability under continuous operation has been reported in PATPD-based composites, a small degradation of the response time in photorefractive devices under continuous operation has been found when improved styrene-based chromophores, with high figure-of-merit, are used. The accumulation of relatively large densities (∼10 17 cm -3) of filled traps is observed even though to first approximation the transport manifold has the lowest ionization potential of all the moieties in the composite, so no apparent deep trapping sites are to be present. The results of spectroscopic studies where the formation of chromophore aggregates is explored and correlated with the formation of hole-trapping sites that dominate the temporal evolution of the photogenerated current density and C 60 anion accumulation after several minutes of continuous operation will be presented and compared with numerical simulations considering a two-trapping site model in materials containing the chromophore DBDC.
• Fuentes-Hernandez, C., Thomas, J., Termine, R., Meredith, G., Peyghambarian, N., Kippelen, B., Barlow, S., Walker, G., Marder, S. R., Yamamoto, M., Cammack, K., & Matsumoto, K. (2004). Video-rate compatible photorefractive polymers with stable dynamic properties under continuous operation. Applied Physics Letters, 85(11), 1877-1879.
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  Abstract: The features of photorefractive polymer composites that exhibited stable dynamic properties under continuous operation were investigated. The sample polymer composite materials was based on a bis-triarylamine side-chain polymer matrix with a low ionization potential. The exposure of the grating dynamics was measured to analyze the role of the accumulation of C 60 anions on the dynamic response. The results show that with a 50-ms write-erase cycle at an intensity of 0.5 W/cm 2, these samples can undergo more than 160 000 cycles without any loss in their photorefractive properties.
• Hocdé, S., Jiang, S., Peng, X., Peyghambarian, N., Luo, T., & Morrell, M. (2004). Er³⁺ doped boro-tellurite glasses for 1.5 μm broadband amplification. Optical Materials, 25(2), 149-156.
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  Abstract: B2O3 has been introduced in Er3+-doped tellurite glasses in order to increase their phonon energy and the multiphonon relaxation rate of the Er3+:4I11/2→ 4I13/2 transition, which will allow efficient 980 nm pumping. The inclusion of additional glass components such as GeO2 and Al2O3 has been shown to enhance the thermal stability of the boro-tellurite glasses. No crystallization peak (Tc) was observed in glass samples containing GeO2 and Al2O 3. The suitability of these boro-tellurite glasses as host for broadband erbium-doped fiber amplifiers and their advantages over the other tellurite glasses are discussed. © 2003 Published by Elsevier B.V.
• Kost, A. R., Sun, X., Peyghambarian, N., Eradat, N., Selvig, E., Fimland, B., & Chow, D. H. (2004). Enhanced photoluminescence from GaAsSb quantum wells. Applied Physics Letters, 85(23), 5631-5633.
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  Abstract: We describe promising semiconductor materials for optoelectronics. GaAsSb/AlSb quantum wells on GaSb substrates show photoluminescence near 1.54 μm (0.8 eV) that increases with increasing arsenic fraction. The materials can be monolithically integrated with AlGaSb/AlSb or AlGaAsSb/AlAsSb Bragg mirrors. © 2004 American Institute of Physics.
• Peng, X., Song, F., Gonokami, M., Jiang, S., & Peyghambarian, N. (2004). Temperature dependence of the wavelength and threshold of fiber-taper-coupled L-band Er ³⁺-doped tellurite glass microsphere laser. Proceedings of SPIE - The International Society for Optical Engineering, 5350, 191-198.
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  Abstract: We report on the temperature dependence of L-band laser emission of fiber-taper-coupled Er 3+-doped tellurite glass microsphere. Pumping at 1480nm instead of 975nm was used to enhance the coupling efficiency, reduce the internal thermal effect, and increase the output laser emission. The microsphere laser emission threshold increased and the emitted laser wavelength shifted with temperature. The experimental results are explained with a quasi-four-level model, showing that a significant reduction of laser threshold can be achieved at lower temperatures and higher Q values of this microsphere laser.
• Spiegelberg, C., Geng, J., Yongdan, H. u., Kaneda, Y., Jiang, S., & Peyghambarian, N. (2004). Low-Noise Narrow-Linewidth Fiber Laser at 1550 nm (June 2003). Journal of Lightwave Technology, 22(1), 57-62.
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  Abstract: We present a compact integrated fiber laser with more than 200 mW of output power. It combines polarized fiber output with very narrow linewidth of less than 2 kHz. The coherence length of the laser is measured to be longer than 5 km. The laser features high mode stability of less than ±10 MHz over hours. The relative intensity noise (RIN) spectrum is dominated by a peak at the relaxation oscillation frequency and is shot-noise limited otherwise. The RIN peak at 1 MHz is reduced to ∼ -130 dB/Hz by integrating a negative feedback circuit. In addition to thermal wavelength tuning, the laser frequency can be modulated at a bandwidth of up to 10 kHz via the piezoelectric effect.
• Tay, S., Eralp, M., Thomas, J., Guoqiang, L. i., Kippelen, B., Meredith, G., Scülzgen, A., Peyghambarian, N., & Marder, S. M. (2004). Novel IR-sensitive photorefractive polymer composite. OSA Trends in Optics and Photonics Series, 96 A, 313-315.
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  Abstract: We demonstrate the first recording of photorefractive gratings in polymer thin-films at a wavelength of 1550 nm. Our results open the window for the application of polymeric photorefractive devices in optical communication. © 2003 Optical Society of America.
• Tay, S., Thomas, J., Eralp, M., Guoqiang, L. i., Kippelen, B., Marder, S. R., Meredith, G., Schülzgen, A., & Peyghambarian, N. (2004). Photorefractive polymer composite operating at the optical communication wavelength of 1550 nm. Applied Physics Letters, 85(20), 4561-4563.
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  Abstract: A photorefractive polymer composite sensitized at 1550 nm through direct two-photon absorption has been developed. We show an external diffraction efficiency of 3% in four-wave-mixing experiments and perform holographic reconstruction of distorted images utilizing thin-film devices made of this polymer composite. Amongst other potential applications, the demonstration of accurate, dynamic aberration correction through holography in this all-organic photorefractive device presents an alternative to complex adaptive optics systems currently employed in through-air optical communication links. © 2004 American Institute of Physics.
• Thomas, J., Eralp, M., Tay, S., Guogiang, L. i., Marder, S. R., Meredith, G., Schülzgen, A., Norwood, R. A., & Peyghambarian, N. (2004). Near-infrared photorefractive polymer composites with high diffraction efficiency and fast response time. Proceedings of SPIE - The International Society for Optical Engineering, 5521, 1-8.
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  Abstract: We describe the material characteristics and photorefractive properties of novel tetraphenyldiaminobiphenyl (TPD) based polymer composites that were developed for operation wavelengths up to 1 micron. With an optimized composite, we demonstrated more than 50% external diffraction efficiency coupled with a fast response time of about 35 ms at 980 nm. In addition to this high performing composite, we have developed a composite with high two beam coupling gain (300 cm -1). To accomplish these attractive photorefractive properties in the near-infrared, we explored the chemical flexibility of the guest-host approach. We employed a new dye with enhanced near-infrared absorption to extend the sensitivity into this long wavelength range. Styrene-based chromophores were utilized to enable high refractive index modulation. We explored ellipsometry as well as photo-conductivity measurements to optimize the composition of the composites. In addition to the composites that contain a single chromophore species, we also analyzed samples prepared with a mixture of chromophores. Our studies reveal the potential of this new polymer-composite family to extend the operation wavelength of the photorefractive materials to even longer wavelengths. Attractive photorefractive properties coupled with long wavelength sensitivity make these materials potential candidates for imaging and communication applications.
• Thomas, J., Fuentes-Hernandez, C., Yamamoto, M., Cammack, K., Matsumoto, K., Walker, G. A., Barlow, S., Kippelen, B., Meredith, G., Marder, S. R., & Peyghambarian, N. (2004). Bistriarylamine polymer-based composites for photorefractive applications. Advanced Materials, 16(22), 2032-2036.
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  Abstract: Photorefractive (PR) composites based on a new polymer, poly(acrylic tetraphenyldiaminobiphenol) (PATPD) were investigated. The development and performance of PATPD-based composites with stable video-rate compatible response times over large exposures was demonstrated. The composites show reasonable phase stability while maintaining diffraction efficiency and gain coefficients. It was found that the response time in fast PR polymers can be limited by the photoconducting properties rather than by orientational diffusion.
• West, B. R., Madasamy, P., Peyghambarian, N., & Honkanen, S. (2004). Modeling of ion-exchanged glass waveguide structures. Journal of Non-Crystalline Solids, 347(1-3), 18-26.
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  Abstract: Glass waveguide devices fabricated by ion exchange have evolved to the point where conventional assumptions of waveguide symmetry and mutual independence are no longer valid. We describe a modeling tool that allows for the presence of an arbitrary, nonhomogeneous electric field distribution during the ion exchange process. An asymmetric waveguide produced by selective field-assisted burial is modeled and discussed. A directional coupler fabricated by field-assisted thermal ion exchange and subsequent field-assisted burial is modeled, and it is shown that a proximity effect exists in which the waveguides exert a mutual influence upon each other during processing. © 2004 Elsevier B.V. All rights reserved.
• Winiarz, J. G., Ghebremichael, F., Thomas, J., Meredith, G., & Peyghambarian, N. (2004). Dynamic correction of a distorted image using a photorefractive polymeric composite. Optics Express, 12(11), 2517-2528.
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  PMID: 19475090;Abstract: We demonstrate, for the first time, the dynamic correction of aberrated images in real-time using a polymeric composite with fast response times. The current novel experimental design is capable of restoring a phase aberrated, image carrying laser beam, to nearly its original quality. The ability to reconstruct images in real-time is demonstrated through the changing of the aberrating medium at various speeds. In addition, this technique allows for the correction of images in motion, demonstrated through the oscillatory movement of the resolution target. We also have demonstrated that important parameters of the materials in the study such as response times, diffraction efficiencies and optical gains all retain high figures of merit values under the current experimental conditions. © 2004 Optical Society of America.
• Yliniemi, S., West, B. R., Aalto, T., Madasamy, P., Peyghambarian, N., & Honkanen, S. (2004). Buried ion-exchanged glass waveguides featuring low birefringence with a broad range of waveguide widths. Proceedings of SPIE - The International Society for Optical Engineering, 5451, 558-564.
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  Abstract: Optical communications networks require integrated photonic components with negligible polarization dependence, which typically means that the waveguides must feature very low birefringence. Recent studies have shown that waveguides with low birefringence can be obtained, e.g., by using silica on Si waveguides and by buried ion-exchanged glass waveguides. However, many integrated photonic circuits consist of waveguides with varying widths. Therefore, low birefringence is consequently required for waveguides having different widths. This is a difficult task for most waveguide fabrication technologies. In this paper we present theoretical and experimental results on waveguide birefringence for buried silver ion-exchanged glass waveguides. We show that the waveguide birefringence is on the order of 106 for waveguide mask opening widths ranging from 2 to 9 μm. The measured values are in good agreement with the values calculated with our modeling software for ion-exchanged glass waveguides. This unique feature of ionexchanged waveguides may be of significant importance in a wide variety of integrated photonic circuits requiring polarization independent operation.
• Enami, Y., Kawazu, M., Jen, A. K., Meredith, G., & Peyghambarian, N. (2003). Polarization-Insensitive Transition Between Sol-Gel Waveguide and Electrooptic Polymer and Intensity Modulation for All-Optical Networks. Journal of Lightwave Technology, 21(9), 2053-2060.
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  Abstract: An intensity modulation using a hybrid electrooptic (EO) polymer/sol-gel straight channel waveguide, useful in the 1550-nm wavelength regime is demonstrated without using Mach-Zehnder interferometric waveguide. The sol-gel waveguide is selectively buried so that a vertical transition into and out of an EO polymer coated on the sol-gel waveguide is arranged. The throughput ratio for transverse electric (TE) and transverse magnetic (TM) modes of the light coupled out of the hybrid waveguide is improved up to 0.9 dB with the help of reduced birefringence of the EO polymer after corona poling. We show that the fabrication process of such hybrid-type waveguides enables production of a phase modulator operating at 1550-nm wavelength. The fabricated straight channel waveguide modulator exhibits stable- and high-intensity modulation efficiency (82%) using a simple cross-polarization setup after the polarization dependence is reduced. We demonstrate an all wet-etching process to fabricate polymeric EO modulators.
• Enami, Y., Meredith, G., Peyghambarian, N., & Jen, A. K. (2003). Hybrid electro-optic polymer/sol-gel waveguide modulator fabricated by all-wet etching process. Applied Physics Letters, 83(23), 4692-4694.
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  Abstract: The fabrication of a hybrid electro-optic polymer (EOP)/sol-gel waveguide modulator by all-wet etching process was discussed. Sol-gel overcladding was used. Optical confinement in the EOP that enables adiabatic transition between the waveguides was also discussed. It was found that hybrid approach has advantages for coupling loss, waveguide and signal stability. The results also show that if thickness of the EOP was increased to 0.9 μm in a laterally confined structure it reduces the V π to 22 V.
• Enami, Y., Meredith, G., Peyghambarian, N., Kawazu, M., & Jen, A. K. (2003). Hybrid electro-optic polymer and selectively buried sol-gel waveguides. Applied Physics Letters, 82(4), 490-492.
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  Abstract: An approach to utilize electro-optically (EO) active polymers in hybrid waveguide structures was discussed. A guided mode was made to undergo adiabatic transitions from sol-gel waveguide up into the EO polymer and back by selectively exposing the core of a buried channel guide, overcoating with an EO polymer, and using appropriately tapered transition zones. The demonstration of the EO modulation verified that the approach required smooth vertical transitions of intensity between sol-gel waveguides and the EO polymer overlayer to obtain efficient EO modulation.
• Fardad, A., Liang, W., Zhang, Y., Case, B., Jiang, S., & Peyghambarian, N. (2003). Halogenation of ORMOSIL: A Promising Rout for Tailoring Optical Absorptions. Materials Research Society Symposium - Proceedings, 771, 43-48.
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  Abstract: Fluorinated and photo-imageable precursors are synthesized through a Barbier-Grignard reaction for 1550-nm window. The precursors are used for the sol-gel process of integrated optic components for silica-on-silicon technology. Material compositions and process parameters are optimized to achieve internal absorptions
• Fardad, A., Zhang, Y., Liang, W., Morrell, M., Staples, R., Jiang, S., & Peyghambarian, N. (2003). Absorption Controlled Photo-Imageable Silanes for Integrated Optics. Conference on Optical Fiber Communication, Technical Digest Series, 86, 324-325.
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  Abstract: A new class of fluoro-substituted hybrid organic-inorganic materials for integrated optics was proposed. Material composition and process parameters were optimized to achieve minimum internal absorptions and propagation losses. Beam splitters were designed and fabricated, which exhibit
• Fuentes-Hernandez, C., Thomas, J., Termine, R., Eralp, M., Yamamoto, M., Cammack, K., Matsumoto, K., Barlow, S., Walker, G., Meredith, G., Peyghambarian, N., Kippelen, B., & Marder, S. R. (2003). Photorefractive polymers based on bis-trianlamine side-chain polymers. Proceedings of SPIE - The International Society for Optical Engineering, 5216, 83-90.
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  Abstract: We report on the photorefractive properties of two polymer composites that utilize a new bis-triarylamine side-chain polymer matrix. Correctly locating the frontier orbitals of the new transport manifold with respect to the HOMO levels of chromophores, allows stable continuous operation over exposure levels of more that 4 kJ/cm 2 when samples are electrically biased at 57 V/μm. This operational stability is combined with video-rate compatible grating build-up times and a dynamic range that allows index modulations of 3 × 10 -3 and gain coefficients on the order of 100 cm -1 at moderate fields. The thermal stability of one of the composites reported is excellent, showing no signs of phase separation even after one week at 60° C. A comparison with the stability of composites where the new matrix was replaced by PVK is also presented.
• Kadono, K., Yazawa, T., Jiang, S., Porque, J., Hwang, B., & Peyghambarian, N. (2003). Rate equation analysis and energy transfer of Er³⁺-doped Ga ₂S₃-GeS₂-La₂S₃ glasses. Journal of Non-Crystalline Solids, 331(1-3), 79-90.
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  Abstract: Decay curves of 1.5 μm (4I13/2) and 1.0 μm (4I11/2) emissions from Er3+ ions in Ga 2S3-GeS2-La2S3 glasses were measured by the excitation of a 1.5 μm and a 980 nm laser diode pump. The decay curves were simulated using rate equations for a model consisting of six levels of the Er3+ from the ground state. The rate equations contained five unknown parameters, i.e., excited state absorption cross sections of 4I13/2 → 4I9/2 (σesa24) for 1.5 μm excitation and 4I 11/2 → 4F7/2 (σesa36) for 980 nm excitation, cooperative upconversion coefficients of ( 4I13/2, 4I13/2) → ( 4I9/2, 4I15/2) (C2) and (4I11/2, 4I11/2) → ( 4F7/2, 4I15/2) (C3), and an energy back-transfer coefficient of (4I9/2, 4I15/2) → (4I13/2, 4I13/2) (C2r). These parameters were estimated by fitting the simulated curves to the measured ones. The obtained values were σesa24 = 0.3 × 10-20 cm2, σesa36 = 0.5 × 10-20 cm2, C 2 = 30-40 × 10-18 cm3/s, C3 = 20-25 × 10-18 cm3/s, and C2r = 5 × 10-18 cm3/s. © 2003 Elsevier B.V. All rights reserved.
• Kippelen, B., & Peyghambarian, N. (2003). Photorefractive polymers and their applications. Advances in Polymer Science, 161, 87-156.
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  Abstract: Photorefractive polymers exhibit large refractive index changes when exposed to low power laser beams. When the optical excitation consists of two interfering coherent beams, the periodic light distribution produces a periodic refractive index modulation. The resulting index change produces a hologram in the volume of the polymer film. The hologram can be reconstructed by diffracting a third laser beam on the periodic index modulation. In contrast to many physical processes that can be used to generate a refractive index change, the photorefractive effect is fully reversible, meaning that the recorded holograms can be erased with a spatially uniform light beam. This reversibility makes photorefractive polymers suitable for real-time holographic applications. The mechanism that leads to the formation of a photorefractive index modulation involves the formation of an internal electric field through the absorption of light, the generation of carriers, their transport and trapping over macroscopic distances. The resulting electric field produces a refractive index change through orientational or non-linear optical effects. Due to the transport process, the index modulation amplitude is phase shifted with respect to the periodic light distribution produced by the interfering optical beams that generate the hologram. This phase shift enables the coherent energy transfer between two beams propagating in a thick photorefractive material. This property, referred to as two-beam coupling, is used to build optical amplifiers. Hence, photorefractive materials are also playing a role in imaging applications. Discovered and studied for several decades mainly in inorganic crystals and semiconductors, the photorefractive effect has not yet found wide spread commercial applications. This can be attributed to the difficulties associated with the growth of crystals, and to the high cost of optical and optomechanical components necessary for the development of complete optical systems. With the emergence of novel low cost plastic optical components that can be mass produced by techniques such as injection molding, the cost and the weight of optical components is decreasing rapidly. This trend together with the advances made in fabricating integrated laser sources at lower cost provide a great momentum to the development of new optical processing technologies. As real-time optical recording and processing media, photorefractive polymers are expected to play a major role in these technologies. The optical, physical, and chemical properties of photorefractive polymers are outlined and discussed. Current material classes and their respective merits and future challenges are presented together with examples of applications.
• Lin, H., Jiang, S., Jianfeng, W. u., Song, F., Peyghambarian, N., & Pun, E. Y. (2003). Er³⁺ doped Na₂O-Nb₂O₅-TeO₂ glasses for optical waveguide laser and amplifier. Journal of Physics D: Applied Physics, 36(7), 812-817.
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  Abstract: Er3+ doped Na2O-Nb2O5-TeO2 (NNT) glasses suitable for making optical waveguide devices has been fabricated and characterized. Intense 1.53 μm infrared fluorescence and green upconversion luminescence were observed under 975 nm diode laser and 798 nm laser excitation. The optical absorption, the Judd-Ofelt parameters and the spontaneous transition probabilities have been measured and calculated. The quantum efficiency of 1.53 μm emission band is proved to be ∼100%. The maximum emission cross-section is 1.02 × 10-20 cm2 at 1.533 μm, and it is more than 30% higher than the values in silicate and phosphate glasses. Under 798 nm excitation, strong green and weak red upconversion luminescence was observed at room temperature. The 546 nm green band shows a broad full-width at half-maximum of 16 nm. Intense and broad green upconversion fluorescence in Er3+ doped NNT glass can be used in colour display, undersea communication and infrared sensor. High concentration of Na2O is a benefit to developing waveguide device from the glass.
• Lin, H., Meredith, G., Jiang, S., Peng, X., Luo, T., Peyghambarian, N., & Pun, E. Y. (2003). Optical transitions and visible upconversion in Er³⁺ doped niobic tellurite glass. Journal of Applied Physics, 93(1), 186-191.
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  Abstract: Optical transitions and visible upconversion in Er3+ doped niobic tellurite glass were investigated. Under 975 nm diode laser and laser excitation, intense and broad 1.53 μm infrared fluorescence and visible upconversion luminescence were observed. The maximum emission cross section was observed to be 8.52×10-21 cm2 at 1.532 μm.
• Madasamy, P., Honkanen, S., Geraghty, D. F., & Peyghambarian, N. (2003). Single-mode tapered waveguide laser in Er-doped glass with multimode-diode pumping. Applied Physics Letters, 82(9), 1332-1334.
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  Abstract: A demonstration of a planar waveguide laser configuration for single-mode operation around 1550 nm using cost-effective multimode diode pumping was reported. The laser was fabricated by Ag film ion exchange in a hybrid phosphate glass. A single transverse mode waveguide laser output power of 54 mW was measured. It was anticipated that the laser performance could be greatly improved by optimizing the cavity and the waveguide index profile.
• Madasamy, P., Honkanen, S., Geraghty, D., & Peyghambarian, N. (2003). Single Mode Tapered Waveguide Laser in Erdoped Glass with Multimode-Diode Pumping. Conference on Optical Fiber Communication, Technical Digest Series, 86, 242-243.
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  Abstract: A planar waveguide laser configuration for single mode operation around the 1550 nm region using multimode-diode pumping was presented. The flexibility of tailoring the asymmetry of planar waveguides was advantageously utilized in coupling light from broad area pump sources with simple optics. The device was fabricated by Ag film ion exchange in a hybrid phosphate glass having Er-doped and passive regions monolithically integrated in a single substrate. A single transverse mode waveguide output power of 54 mW was obtained.
• Madasamy, P., West, B. R., Morrell, M. M., Geraghty, D. F., Honkanen, S., & Peyghambarian, N. (2003). Buried ion-exchanged glass waveguides: Burial-depth dependence on waveguide width. Optics Letters, 28(13), 1132-1134.
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  PMID: 12879931;Abstract: A detailed theoretical and experimental study of the depth dependence of buried ion-exchanged waveguides on waveguide width is reported. Modeling, which includes the effect of nonhomogeneous time-dependent electric field distribution, agrees well with our experiments showing that burial depth increases linearly with waveguide width. These results may be used in the proper design of integrated optical circuits that need waveguides of different widths at different sections, such as arrayed waveguide gratings. © 2003 Optical Society of America.
• Mune, K., Naito, R., Fukuoka, T., Mochizuki, A., Matsumoto, K., Yurt, N., Meredith, G., Jabbour, G., & Peyghambarian, N. (2003). Fabrication of low loss optical waveguides using a novel photosensitive polyimide. Proceedings of SPIE - The International Society for Optical Engineering, 4997, 103-108.
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  Abstract: Fabrication of optical waveguides by a simple patterning process using photosensitive polyimide (PSPI) is described. Light waveguide based on PSPI was fabricated by photolithographic processing without use of dry etching process. The PSPI varnish is comprised of polyamic acid (PAA) which was made from fluorinated diamine and fluorinated tetracarboxylic dianhydride, and photosensitizer. The PSPI has the following characteristics: glass transition temperature (Tg) of 330 °C, coefficient of thermal expansion of 40 ppm/K. Moreover the PSPI is colorless, and posses low absorption at 1.3 and 1.55μm. The sidewalls and the surfaces of the fabricated waveguide are very smooth, which is essential for the low loss optical mode propagation and lower scattering of the mode due to the imperfections. Single and multimode buried ridge waveguides on quartz glass substrate were fabricated and tested. Optical propagation losses were measured by standard cut back method and found to be as low as 0.4 dB/cm @ 1.55 μm. This fabrication process would be expected to contribute to low cost production for high performance opto-electronic devices.
• Peng, X., Song, F., Jiang, S., Gonokami, M., & Peyghambarian, N. (2003). Fiber-taper-coupled L-band Er³⁺-doped tellurite glass microsphere laser. Proceedings of SPIE - The International Society for Optical Engineering, 4990, 22-29.
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  Abstract: A fiber-taper-coupled L-band microsphere laser was proposed and demonstrated. Er3+-doped tellurite glass was used to fabricate the microspheres. The microspheres were made by a novel spin method. The pump and emission light were coupled in and out of the microsphere modes with a tapered fiber. 975nm pumped L-band single/multi-mode microsphere lasers were demonstrated. The laser can be tuned in L-band. We call Er3+-doped microsphere laser as EDML.
• Peng, X., Song, F., Jiang, S., Peyghambarian, N., Kuwata-Gonokami, M., & Lei, X. u. (2003). Fiber-taper-coupled L-band Er ³⁺-doped tellurite glass microsphere laser. Applied Physics Letters, 82(10), 1497-1499.
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  Abstract: Fiber-taper tellurite coupled L-band Er 3+ -doped tellurite glass microspheres lasers were fabricated. The doped glasses were prepared using a gold crucible in an electric heated furnace. Bulk samples were used for spectroscopic characterization and other property measurements. The emission cross section spectrum was calculated from the absorption cross section spectrum and emission spectrum. The microsphere laser was demonstrated successfully.
• Peng, X., Song, F., Kuwata-Gonokami, M., Jiang, S., & Peyghambarian, N. (2003). Temperature dependence of the wavelength and threshold of fiber-taper-coupled L-band Er ³⁺-doped tellurite glass microsphere laser. Applied Physics Letters, 83(26), 5380-5382.
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  Abstract: The significance of temperature dependence of the wavelength and the laser emission threshold of fiber-taper-coupled Er 3+-doped tellurite glass microsphere was analyzed. A rise in the microsphere laser emission threshold and a shift in emitted laser wavelength occurred with the temperature. A shift in the resonant wavelength of the pumping light was caused by the changes of the size and refractive index of the microsphere. A quasi-four-level model was used to show the reduction of laser threshold, achieved at lower temperatures and higher Q values of the microsphere laser.
• Peyghambarian, N., Madasamy, P., West, B. R., Morrell, M. M., Geraghty, D. F., Honkanen, S., & Peyghambarian, N. N. (2003). Buried ion-exchanged glass waveguides: burial-depth dependence on waveguide width. Optics letters, 28(13).
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  A detailed theoretical and experimental study of the depth dependence of buried ion-exchanged waveguides on waveguide width is reported. Modeling, which includes the effect of nonhomogeneous time-dependent electric field distribution, agrees well with our experiments showing that burial depth increases linearly with waveguide width. These results may be used in the proper design of integrated optical circuits that need waveguides of different widths at different sections, such as arrayed waveguide gratings.
• Seneschal, K., Smektala, F., Jiang, S., Luo, T., Bureau, B., Lucas, J., & Peyghambarian, N. (2003). Alkaline-free phosphate glasses for ultra compact optical fiber amplifiers at 1.5 μm. Journal of Non-Crystalline Solids, 324(1-2), 179-186.
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  Abstract: New alkaline-free phosphate glass compositions are presented. A phosphate glass with a temperature coefficient of refractive index close to zero and a good chemical durability can be achieved. These new glass compositions are very promising for high quality optical fibers with a constant mode profile, and erbium-doped fiber amplifiers with a high gain per unit length. © 2003 Elsevier B.V. All rights reserved.
• Sorbello, G., Taccheo, S., Valle, G. D., Laporta, P., Cianci, E., Foglietti, V., Jiang, S., & Peyghambarian, N. (2003). Twisted-mode single-frequency Er-Yb waveguide laser at 1.5 μm. Optical and Quantum Electronics, 35(7), 669-674.
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  Abstract: Robust single-frequency operation of an erbium-ytterbium glass waveguide laser based on the twisted-mode technique is demonstrated. A single-mode output power of ∼0.7 mW with relative-intensity-noise peak value of -90 dB/Hz has been obtained.
• Yongdan, H. u., Spiegelberg, C., Geng, J., Luo, T., Kaneda, Y., Wang, J., Hocde, S., Jiang, S., & Peyghambarian, N. (2003). High power single-frequency narrow-linewidth erbium-doped fiber laser. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 2, 794-795.
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  Abstract: The first demonstration of a 200-mW stable single-frequency narrow-linewidth distributed Bragg reflector erbium-doped fiber lasers (DBR EDFL) was reported. In particular, the fiber laser was constructed by fusion splicing two FBGs with a 2-cm erbium doped fiber. With this unique laser, it was believed that many applications in both old and new territories can be explored.
• Blanche, P. A., Kippelen, B., Schülzgen, A., Fuentes-Hernandez, C., Ramos-Ortiz, G., Wang, J. F., Hendrickx, E., Peyghambarian, N., & Marder, S. R. (2002). Photorefractive polymers sensitized by two-photon absorption. Optics Letters, 27(1), 19-21.
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  PMID: 18007702;Abstract: We demonstrate the recording of holograms and their nondestructive readout in a photorefractive polymer, using two-photon absorption. Sensitivity is provided by the excitation of the electroactive chromophore with femtosecond pulses, followed by charge injection into the photoconducting poly(N-vinylcarbazole) matrix. The holograms can be fully erased with a pulsed laser source but are insensitive to cw laser beams with the same wavelength. Studies of the field and intensity dependence of the diffraction efficiency indicate that the holograms are formed through the photorefractive effect. © 2002 Optical Society of America.
• Herlocker, J. A., Fuentes-Hernandez, C., Wang, J. F., Peyghambarian, N., Kippelen, B., Zhang, Q., & Marder, S. R. (2002). Photorefractive polymer composites fabricated by injection molding. Applied Physics Letters, 80(7), 1156-1158.
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  Abstract: We report on the fabrication of bulk samples of photorefractive polymers using the injection molding technique. The photorefractive properties of these materials are evaluated by four-wave mixing and two-beam coupling experiments. Samples with good optical quality, high diffraction efficiency, and net optical gain are obtained. © 2002 American Institute of Physics.
• Jabbour, G. E., Wang, J. -., & Peyghambarian, N. (2002). High-efficiency organic electrophophorescent devices through balance of charge injection. Applied Physics Letters, 80(11), 2026-2028.
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  Abstract: Balancing the charge injection plays an important role not only in fluorescence-based organic light-emitting devices, but also in the performance of the recently introduced organic electrophosphorescent devices. By achieving a better balance in the injected charges, it is possible to fabricate devices based on the pure red emitter 2, 3, 7, 8, 12, 13, 17, 18-octaethyl-21H, 23H-porphine, PtOEP, with external quantum efficiency close to 9%. © 2002 American Institute of Physics.
• Jose, G., Taccheo, S., Sorbello, G., Migliorati, D., Foglietti, V., Cianci, E., Jiang, S., Peyghambarian, N., & Laporta, P. (2002). Multiwavelength waveguide laser array in C-band. Electronics Letters, 38(21), 1275-1276.
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  Abstract: The performance of a multiwavelength waveguide laser array operating in the C-band of optical communication was studied using fiber Bragg gratings (FBGs). Stable single frequency operation was also analyzed at chosen wavelengths ranging from 1533 to 1560 nm. The results showed that the waveguide laser array can be suitable for multiwavelength sources operating in the whole C-band for metro-WDM applications.
• Kippelen, B., Blanche, P. -., Schülzgen, A., Fuentes-Hernandez, C., Ramos-Ortiz, G., Wang, J. -., Peyghambarian, N., Marder, S. R., Leclercq, A., Beljonne, D., & Brédas, J. (2002). Photorefractive polymers with non-destructive readout. Advanced Functional Materials, 12(9), 615-620.
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  Abstract: Photorefractive polymers are suitable for real-time holographic applications. Since the recording and readout of a hologram is carried out with laser beams with the same wavelength, the readout process partially erases the stored information, a problem common to all current photorefractive materials and referred to as destructive readout. In this paper we describe photorefractive polymers that are sensitized by two-photon absorption. Holographic recording is achieved with high-intensity writing beams and readout using low light intensity, but high power beams. Using this nonlinear recording scheme, non-destructive readout was demonstrated.
• Kippelen, B., Marder, S. R., & Peyghambarian, N. (2002). Photorefractive polymers for real-time holography fabricated by injection molding. Optics and Photonics News, 13(12), 42-.
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  Abstract: The fabrication of photorefractive polymers and their applications in real-time holography was discussed. The injection molding process was used in the fabrication and photorefractivity was obtained by adding a sensitizer and a bifunctional dopant. A diffraction efficiency of 20% was observed in the photorefractive sample made by injection molding process.
• Madasamy, P., Conti, G. N., Poyhonen, P., Hu, Y., Morrell, M. M., Geraghty, D. F., Honkanen, S., & Peyghambarian, N. (2002). Waveguide distributed Bragg reflector laser arrays in erbium doped glass made by dry Ag film ion exchange. Optical Engineering, 41(5), 1084-1086.
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  Abstract: We demonstrate a distributed Bragg reflector (DBR) waveguide laser array by using an Ag film ion-exchange technique. We achieve an output power of 11 mW at 1540 nm for a coupled pump power of 145 mW, with a threshold of 60 mW and slope efficiency of 13%. The thin film ion exchange produces the highest index change possible at the surface, due to the ion exchange technique. Hence a wide array of wavelengths can be implemented in a single chip. We demonstrate a lasing wavelength range of 2.1 nm (1548.6 to 1550.7 nm) in an array with a single grating. Since the index change due to our process is large, we can fine tune the wavelengths of the array to fall on International Telecommunication Union (ITU) grid wavelengths by annealing. We demonstrate fine tuning of the wavelength for a channel from 1540.2 to 1540 nm, ITU specified wavelength, by annealing.
• Peng, X., Song, F., Jiang, S., Gonokami, M., & Peyghambarian, N. (2002). Signal enhancement in Er³⁺ doped telluride glass microsphere. Proceedings of SPIE - The International Society for Optical Engineering, 4645, 148-155.
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  Abstract: Microstructure resonators have attracted considerable attention because of their versatility for signal processing applications. We use our Er3+ doped telluride glass to fabricate Er3+ glass microsphere. The excitation of whispering-gallery modes is realized by coupling from an angle-polished single-mode optical fiber tip to an optical microsphere cavity. In the experimental setup, one fiber was used as an input coupler and the other fiber was used as an output coupler. 975nm fiber pigtailed laser diode was used to side pump the microspheres. Very nice whispering-gallery modes (WGM's) near 1.5μm were observed successfully. Signal enhancement was observed in this Er3+ doped telluride glass microsphere with a radius around 50μm. The best enhancement of this Er3+ doped telluride glass microsphere reaches 12dB.
• Righini, G. C., Brenci, M., Forastiere, M. A., Pelli, S., Ricci, G., Conti, G. N., Peyghambarian, N., Ferrari, M., & Montagna, M. (2002). Rare-earth-doped glasses and ion-exchanged integrated optical amplifiers and lasers. Philosophical Magazine B: Physics of Condensed Matter; Statistical Mechanics, Electronic, Optical and Magnetic Properties, 82(6), 721-734.
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  Abstract: Rare-earth-doped (Er-, Yb- and Er+Yb-doped) silica glasses have been produced and characterized. Their spectroscopic properties have been assessed and optical amplification devices have been produced therefrom and characterized.
• Song, F., Zhang, C., Ding, X., Jingjun, X. u., Zhang, G., Leigh, M., & Peyghambarian, N. (2002). Determination of thermal focal length and pumping radius in gain medium in laser-diode-pumped Nd:YVO₄ lasers. Applied Physics Letters, 81(12), 2145-2147.
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  Abstract: A method to determine the focal length of a thermal lens and pumping laser beam waist in the gain medium in laser-diode-pumped solid-state lasers is presented. This method, using resonator transform circle theory, is both simple and reliable. The measured focal length of the thermal lens is used to calculate the beam waist of pumping laser inside the gain medium. The effect of the thermal lens on the output power is also measured and analyzed. © 2002 American Institute of Physics. © 2002 American Institute of Physics.
• Sorbello, G., Taccheo, S., Ramponi, R., Foglietti, V., Jiang, S., Peyghambarian, N., & Laporta, P. (2002). Laser action in ion-exchanged waveguides fabricated on Er-Yb-doped phosphate glasses using planar technology. Proceedings of SPIE - The International Society for Optical Engineering, 4645, 165-173.
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  Abstract: Waveguide laser arrays operating at 1.5 μm have been fabricated on Er:Yb-doped glass substrates by a two-step silver-sodium ion-exchange process based on thermal diffusion followed by a field-assisted burial step. The fabrication parameters have been optimized to achieve low propagation losses and good mode matching between waveguide channels and standard single-mode output fibers. Each laser cavity is formed by two Bragg gratings butt-coupled to the two ends of the channel waveguide. Fiber-coupled output power in excess of 10 mW is readily available from a single channel, when pumped from both sides by two 980-nm laser diodes providing a maximum power of ∼300 mW. Single-longitudinal mode operation with output power of the order of 1 mW has been achieved using narrow reflectivity band (< 30 GHz) Bragg gratings with different laser configurations. The laser operating wavelength can be selected across the whole C-band of optical communications (1530-1565 nm) by changing the Bragg grating peak reflectivity wavelength. A relative intensity noise lower than -150 dB/Hz has been measured for frequencies larger than 2 MHz. Stability of single-frequency operation, low intensity noise and flexibility in the choice of the operating wavelength make this laser array particularly attractive for wavelength division multiplexing optical transmissions.
• Zhang, Y., Hreha, R. D., Jabbour, G. E., Kippelen, B., Peyghambarian, N., & Marder, S. R. (2002). Photo-crosslinkable polymers as hole-transport materials for organic light-emitting diodes. Journal of Materials Chemistry, 12(6), 1703-1708.
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  Abstract: A bis(diarylamino)biphenyl-functionalised methacrylate has been synthesised and polymerised to give a hole-transport polymer; copolymerisation with a chalcone- or cinnamate-functionalised methacrylate affords photocrosslinkable hole-transport polymers that become insoluble upon exposure to ultra-violet irradiation. Organic light-emitting diodes (OLEDs) were fabricated based on both crosslinked and non-crosslinked hole-transport polymers, and the performances of the devices were evaluated.
• Ding, Y., Jiang, S., Luo, T., Hu, Y., & Peyghambarian, N. (2001). Optical waveguides prepared in Er³⁺-doped tellurite glass by Ag⁺- Na⁺ ion-exchange. Proceedings of SPIE - The International Society for Optical Engineering, 4282, 23-30.
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  Abstract: This paper reports the preparation of planar waveguides in an Er3+ doped tellurite glass with a composition, 15Na2O-25WO3-60TeO2-1Er2O 3 (mol%), by Ag+ - Na+ ion-exchange. The glass was chemically stable during ion-exchange process. Single-mode and multi-mode planar and buried waveguides in the tellurite glasses have been prepared, which is the first demonstration of waveguides in tellurite glasses fabricated by ion-exchange technique to the best of our knowledge. The depths of the waveguides could be controlled by varying ion-exchange temperatures and times (290°C to 360°C, and 1h to 34h were used in the paper). The diffusion parameters, diffusion coefficients and activation energy were estimated. It is indicated that the tellurite glass is a prospective candidate for active integrated optics.
• Fuentes-Hernandez, C., Herlocker, J. A., Wang, J. F., Zhang, Y., Marder, S. R., Peyghambarian, N., & Kippelen, B. (2001). Optimization of photorefractive polymers doped with styrene-based chromophores. Proceedings of SPIE - The International Society for Optical Engineering, 4279, 63-68.
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  Abstract: We present a study on the effects of the dark conductivity on the photorefractive performance of polymers doped with styrene-based chromophores. We find that reducing dark conductivity in such composites increases diffraction efficiency and at the same time decreases the response time. We use a polymer composite based on a polyvinylcarbazole matrix doped with 4-Homopiperidinobenzylidenemalononitrile (7-DCST), sensitized with C60, and plasticized with N-ethylcarbazole (ECZ) and butyl benzyl phthalate (BBP). The reduction of the dark conductivity is achieved by coating one of the electrodes with a SiO blocking layer.
• Geraghty, D. F., Provenzano, D., Morrell, M. M., Honkanen, S., Yariv, A., & Peyghambarian, N. (2001). Ion-exchanged waveguide add/drop filter. Proceedings of SPIE - The International Society for Optical Engineering, 4277, 85-90.
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  Abstract: An add/drop filter was demonstrated using ion-exchange waveguides and photowritten Bragg gratings. Surface waveguides were formed in borosilicate glass by silver ion-exchange for the fabrication of add/drop filter. The silicate glass was specially designed for Ag+ ion-exchange to minimize Ag+ reduction to metallic silver and to give a linear dependence of refractive index change on Ag+ concentration.
• Geraghty, D. F., Provenzano, D., Morrell, M., Honkanen, S., Yariv, A., & Peyghambarian, N. (2001). Ion-exchanged waveguide add/drop filter. Electronics Letters, 37(13), 829-831.
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  Abstract: Ion exchanged waveguides and photowritten Bragg gratings were used to fabricate and add/drop filter. The device exhibits 20 dB extinction ratios and 3 dB bandwidths of 0.4 nm (100 GHz) and a polarization dependence of 0.25 nm. Grating optimization, a deep burial step, and optimization of the modes sensitivity to angular misalignment can be used to improve the performance.
• Herlocker, J. A., Fuentes-Hernandez, C., Wang, J. F., Peyghambarian, N., Kippelen, B., Zhang, Y., & Marder, S. R. (2001). Photorefractive properties of polymer composites fabricated by injection molding. Conference on Lasers and Electro-Optics Europe - Technical Digest, 399-.
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  Abstract: The photorefractive properties of an inert polymer obtained after injection moulding were tested and demonstrated for use in industrial processing in manufacture of optoelectronic devices, holography and imaging applications. The polymer was a commercially available acrylic resin, produced by block copolymerization and birefringence reduction. The four wave mixing experiments were carried out for determining the diffraction efficiency and response time.
• Hu, Y., Jiang, S., Sorbello, G., Luo, T., Ding, Y., Hwang, B. -., Kim, J. -., Seo, H. -., & Peyghambarian, N. (2001). Cooperative upconversion in a new high Er-doped tellurite glass. Proceedings of SPIE - The International Society for Optical Engineering, 4282, 57-74.
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  Abstract: A model for population dynamics of Er3+ in tellurite glasses with high erbium concentrations is proposed. Luminescence decay curves from transitions of 4I13/2→ 4I15/2 and 4S3/2→4I15/2 were measured experimentally. Cooperative upconversion coefficients were obtained by numerically solving the rate equations of the model to fit the population dynamics of the 4I13/2 and 4S3/2 levels. The cooperative upconversion coefficient for 4I13/2+4I13/2→ 4I9/2+4I15/2 is found to be 2.74×10-18 cm3/s and for 4I11/2+4I11/2→ 4I15/2+2F7/2 is 1.09×10-18 cm3/s. The model provides a good basis for explaining the experiment data as it shows a high sensitivity to the input fitting parameters. This model can be used to analyze spectroscopic properties of Er3+ ions in glass hosts where various energy levels of Er3+ and transitions between them cannot be neglected.
• Hwang, B., Jiang, S., Luo, T., Seneschal, K., Sorbello, G., Morrell, M., Smektala, F., Honkanen, S., Lucas, J., & Peyghambarian, N. (2001). Performance of high-concentration Er³⁺-doped phosphate fiber amplifiers. IEEE Photonics Technology Letters, 13(3), 197-199.
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  Abstract: The performances of high-concentration Er3+-doped phosphate fiber amplifiers are reported. The amplifiers are characterized in terms of gain, noise figure, and signal saturation power in a co-propagating pump configuration. A net gain of 21 dB and a gain per unit length 3 dB/cm are achieved in a 71-mm Er3+-doped phosphate fiber.
• Jabbour, G. E., & Peyghambarian, N. (2001). Screen printing for organic-based photonics and electronics. Optics and Photonics News, 12(12), 27-.
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  Abstract: The screen printing for organic-based photonics and electronics was discussed. The use of screen printing in the deposition of ultrathin layers of organic materials for use in organic light emitting devices (OLED) was elaborated. The analysis suggested the application of technique in roll-to-roll printing of photonic and electronic components for low-defnition displays, signage and disposable electronics.
• Jabbour, G. E., Radspinner, R., & Peyghambarian, N. (2001). Screen printing for the fabrication of organic light-emitting devices. IEEE Journal on Selected Topics in Quantum Electronics, 7(5), 769-773.
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  Abstract: Lower cost and high-throughput printing techniques, such as screen printing, have a great promise in the fabrication of organic light-emitting devices. We investigate the effects of solution viscosity and screen mesh count on the printed layer thickness and device performance. The results also demonstrate, for the first time to our knowledge, the use of screenprinting to deposit ultrathin layers of less than 15 nm with rms surface roughness of less than 1.5 nm.
• Jabbour, G. E., Radspinner, R., & Peyghambarian, N. (2001). Screen-printing for the fabriction of organic light-emitting devices. Proceedings of SPIE - The International Society for Optical Engineering, 4466, 72-79.
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  Abstract: Lower cost and high throughput printing techniques, such as screen printing, have a great promise in the fabrication of organic light-emitting devices. We investigate the effects of solution viscosity and screen mesh count on the printed layer thickness, and device performance. The results also demonstrate, for the first time to our knowledge, the use screen-printing to deposite an ultra-thin latyers of less than 15 nm with RMS surface roughness of less than 1.5 nm.
• Kärkkäinen, A., Rantala, J. T., Jabbour, M., Liang, C., Bedford, R., Peyghambarian, N., Descour, M. R., & Jabbour, G. E. (2001). Miniaturized organic light emitting diode (OLED) light source for micro-optical systems. Proceedings of SPIE - The International Society for Optical Engineering, 4284, 100-107.
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  Abstract: We present the design and fabrication of miniaturized light sources for micro-optical systems using organic light emitting diodes (OLEDs). These devices can be integrated on a micro-optical table (MOT) using various backplanes. Acceptable angular uniformity of emitted radiance, and a brightness of more than 30,000 cd/m2 can be readily achieved with OLEDs having areas ranging from 0.0003 cm2 to 0.0363 cm2.
• Pardo, D. A., Peyghambarian, N., & Jabbour, G. E. (2001). In situ purification of organic materials for organic light-emitting device fabrication. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 40(8), 4922-4923.
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  Abstract: The direct route to purify, as-deposited, materials for the fabrication of organic light emitting devices (OLED) was analyzed. The in situ purification of 8-tris-hydroxyquinoline aluminum (Alq3) was carried out by pouring the as-received Alq3 in the boron nitride (BN) crucible and capping it with a placed layer of glass wool. The material was heated using ramp and soak schemes at several temperature steps prior to deposition where green-yellow crystallites were observed to grow. The emitted optical power was measured by a calibrated silicon photodiode and converted to the number of photons per second for a specific wavelength.
• Peyghambarian, N. (2001). Novel optical devices for signal processing and transmission. Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest, 2, II748.
• Peyghambarian, N., Marder, S., Koike, Y., & Persoons, A. (2001). Introduction to the issue on organics for photonics. IEEE Journal on Selected Topics in Quantum Electronics, 7(5), 757-.
• Schülzgen, A., Kawabe, Y., Hanamura, E., Yamanaka, A., Blanche, P. -., Lee, J., Sato, H., Naito, M., Dan, N. T., Uchida, S., Tanabe, Y., & Peyghambarian, N. (2001). Two-photon resonant third-harmonic generation in La₂CuO₄. Physical Review Letters, 86(14), 3164-3167.
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  PMID: 11290133;Abstract: The strong third harmonic generation (THG) in La2CO4 was demonstrated and the merit of THG experiments for the investigation of energy states and crystal symmetry of insulating transition-metal oxides was emphasized. Results show an excellent agreement between experimental data and calculations based on the excitonic cluster model, verifying that this model provides an adequate description of the electronic structure in the region of the charge transfer gap. The application of this experimental method to other undoped and doped transition-metal oxides provide further insight into the electronic structure of these important materials.
• Seneschal, K., Jiang, S., Luo, T., Smektala, F., Lucas, J., & Peyghambarian, N. (2001). Er³⁺-doped alkaline free phosphate glasses for optical fiber amplifiers. Proceedings of SPIE - The International Society for Optical Engineering, 4282, 93-100.
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  Abstract: New alkaline free phosphate glass compositions are presented. Phosphate glass with a temperature coefficient of refractive index close to zero and a good chemical durability can be achieved. These new glass compositions are very promising for high quality optical fibers with a constant mode profile, and erbium doped fiber amplifiers with a high gain per unit length.
• Shaheen, S. E., Radspinner, R., Peyghambarian, N., & Jabbour, G. E. (2001). Fabrication of bulk heterojunction plastic solar cells by screen printing. Applied Physics Letters, 79(18), 2996-2998.
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  Abstract: We demonstrate the use of screen printing in the fabrication of ultrasmooth organic-based solar cells. Organic films on the order of several tens of nanometers in thickness and 2.6 nm surface roughness were made. The first-generation screen-printed plastic solar cells demonstrated 4.3% in power conversion efficiency when using an aluminum electrode and 488 nm illumination. © 2001 American Institute of Physics.
• Sorbello, G., Taccheo, S., Laporta, P., Svelto, O., Cianci, E., Foglietti, V., Jiang, S., & Peyghambarian, N. (2001). Singlemode Er:Yb waveguide laser array at 1.5 μm. Electronics Letters, 37(16), 1014-1015.
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  Abstract: An array of waveguide lasers operating at 1533 nm has been fabricated on Er:Yb-doped glass substrate by the silver-sodium ion-exchange technique. The maximum single-frequency output power from a single channel is 0.8 mW, with a relative intensity noise of -82dB/Hz at the relaxation oscillation peak and below approximately -150dB/Hz for frequencies higher than 2 MHz.
• Söderlund, M., Tammela, S., Pöyhönen, P., Leppihalme, M., & Peyghambarian, N. (2001). Amplified spontaneous emission in cladding-pumped L-band erbium-doped fiber amplifiers. IEEE Photonics Technology Letters, 13(1), 22-24.
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  Abstract: Propagation of amplified spontaneous emission (ASE) in cladding-pumped long-wavelength-band erbium-doped fiber amplifiers (EDFAs) is analyzed numerically. Forward and backward ASE power dependence on cladding area is analyzed for both pumping directions. ASE power propagating counter-directionally to the pump is found to experience strong dependence on the cladding area. Increasing the cladding area results in more uniform pump distribution along the EDF, preventing short-wavelength gain and ASE buildup. Quantum conversion efficiency in cladding-pumped L-band EDFAs is discussed.
• Yongdan, H. u., Jiang, S., Luo, T., Seneschal, K., Morrell, M., Smektala, F., Honkanen, S., Lucas, J., & Peyghambarian, N. (2001). Performance of high-concentration Er ³⁺-Yb ³⁺-Codoped phosphate fiber amplifiers. IEEE Photonics Technology Letters, 13(7), 657-659.
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  Abstract: Performance of high-concentration Er 3+-Yb 3+-codoped phosphate fiber amplifiers in a copumping configuration is presented. Gain, noise figure, and output signal saturation power of fiber amplifiers with different lengths are reported. From a 3.6-cm-long fiber, 18-dB internal gain, i.e., 5 dB/cm, for small signal input at 1535 nm, was achieved. To the best of our knowledge, this is the highest gain per unit length for erbium-doped fiber amplifiers ever reported.
• Yongdan, H. u., Jiang, S., Sorbello, G., Luo, T., Ding, Y., Hwang, B., Kim, J., Seo, H., & Peyghambarian, N. (2001). Numerical analyses of the population dynamics and determination of the upconversion coefficients in a new high erbium-doped tellurite glass. Journal of the Optical Society of America B: Optical Physics, 18(12), 1928-1934.
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  Abstract: A model for the population dynamics of Er3+ in tellurite glasses with high erbium concentrations is proposed. Luminescence decay curves from transitions of 4I13/2 → 4I 15/2 and 4S3/2 → 4I 15/2 were measured experimentally. Upconversion coefficients were obtained by numerically solving the rate equations of the model to fit the population dynamics of the 4I13/2 and 4S 3/2 levels. The upconversion coefficient for 4I 13/2 + 4I13/2 → 4I 9/2 + 4I15/2 is found to be 2.74 × 10-18 cm3/s and for 4I11/2 + 4I11/2 → 4I15/2 + 2F7/2 is 1.09 × 10-18 cm3/s. The model provides a good basis for explaining the experiment data because it shows a high sensitivity to the input fitting parameters. This model can be used to analyze transition properties of Er3+ ions in glass hosts, where various energy levels of Er3+ and the transitions between them cannot be neglected. A discussion of upconversion coefficients in tellurite glass in comparison with those in silica, silicate, and phosphate glasses is presented with an explanation of the origin of the differences from the perspective of different glass structures. © 2001 Optical Society of America.
• Auxier, J., Wundke, K., Schulzgen, A., Peyghambarian, N., & Borrelli, N. F. (2000). Luminescence and gain around 1.3 μm in PbS quantum dots. Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest, 385-386.
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  Abstract: Strong luminescence and gain is observed for PbS quantum dot (QD) doped glasses at the 1.3 μm communications wavelength under CW and pulsed laser excitation, respectively, at 980 nm. Thermal treatment of an oxide molten glass is an inexpensive method to manufacture semiconductor quantum dot doped glasses with well-defined exciton peaks and small inhomogeneous broadening. The PbS QDs studied here have radii much smaller than the bulk exciton Bohr radius providing strong quantum confinement effects. As a result, the exciton resonances can be tuned to the communication wavelengths of 1.3 and 1.55 μm by varying the QD size.
• Bellmann, E., Jabbour, G. E., Grubbs, R. H., & Peyghambarian, N. (2000). Hole transport polymers with improved interfacial contact to the anode material. Chemistry of Materials, 12(5), 1349-1353.
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  Abstract: New hole transport polymers have been prepared through copolymerization of a fluorinated triphenyl diamine derivative and trimethoxyvinylsilane. The modification with trimethoxysilane groups has resulted in materials which can be cross-linked through hydrolysis and are capable of forming covalent chemical bonds to oxidic surfaces. Organic light-emitting diodes containing these polymers show decreased operating voltages and enhanced operational stability due to improved interfacial contact between the hole transport layer and the anode.
• Das, S., Geraghty, D., Honkanen, S., & Peyghambarian, N. (2000). MMI splitters by ion-exchange in glass. Proceedings of SPIE - The International Society for Optical Engineering, 3936, 239-247.
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  Abstract: This paper shows the demonstration of Multimode Interference (MMI) power splitters with graded index waveguides using ion-exchange technology. Typically these devices have been fabricated using step index waveguides such as silica waveguides on silicon. The advantages of ion-exchange technology and MMI splitters fabricated by ion-exchange are discussed. The design and simulation results for a 1 * 4 MMI splitter are presented and compared to the experimental results.
• Ding, Y., Jiang, S., Hwang, B., Luo, T., Peyghambarian, N., & Miura, Y. (2000). Spectral properties of erbium-doped lead halotellurite glasses. Proceedings of SPIE - The International Society for Optical Engineering, 3942, 166-173.
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  Abstract: Broadband erbium-doped fiber amplifiers at 1.5 μm band, an important communication band, are generating great interest in order to increase the transmission capacity of wavelength-division-multiplexing (WDM) transmission networks. The host materials for Er3+ doping are very important for obtaining an intrinsically broad amplifier bandwidth. This paper reports the spectral properties of the Er3+ doped lead halotellurite glasses, PbX2-TeO2 (X = F, Cl, Br). The measured absorption and emission spectra were analyzed by Judd-Ofelt and McCumber theories. It was found that Er3+ doped lead halotellurite glasses have a good glass stability, high refractive indices, high absorption and stimulated emission cross sections, and a very broad bandwidth for 1.5 μm absorption and emission. The 1.5 μm band, which has a substantial magnetic dipole transition component, is a special band whose bandwidth increases significantly with the refractive index of the host material. It is expected that the halotellurite glasses will be the promising host materials for 1.5 μm broadband amplification.
• Ding, Y., Jiang, S., Hwang, B., Luo, T., Peyghambarian, N., Himei, Y., Ito, T., & Miura, Y. (2000). Spectral properties of erbium-doped lead halotellurite glasses for 1.5 μm broadband amplification. Optical Materials, 15(2), 123-130.
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  Abstract: The spectral properties of the Er3+-doped lead halotellurite glasses, PbX2-TeO2 (X = F, Cl, Br), were measured and analyzed with Judd-Ofelt and McCumber theories. These glasses showed high refractive indices, high cross-sections for both absorption and stimulated emission, and very broad bandwidths for the 1.5 μm band. The bandwidths of the 1.5 μm band, which have substantial magnetic dipole transition component, increased significantly with the refractive index of the host materials. The halotellurite glasses have very good glass formation ability or glass stability. The halotellurite glasses will be the promising host materials for 1.5 μm broadband amplification.
• Emerich, M., Tasch, S., Resel, R., Leising, G., Freudenmann, R., Hanack, M., Shaheen, S. E., Jabbour, G. E., & Peyghambarian, N. (2000). Hexa-alkoxytriphenylenes as hole transporting materials in stable oleds using Alq₃ as emitting layer. Materials Research Society Symposium - Proceedings, 598, BB11.22.1-BB11.34.6.
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  Abstract: Devices consisting of hexa-alkoxythriphenylene derivatives as hole transport materials and 8-hydroxyquinoline aluminium (Alq3) as emitting layer with ITO as anode and magnesium as cathode are presented. Moreover X-ray diffraction studies of evaporated triphenylene films were performed leading to a better understanding of crystal structure, morphology and the alignment of the triphenylene molecules on the surface of the substrate. © 2000 Materials Research Society.
• Enami, Y., Poyhonen, P., Mathine, D. L., Bashar, A., Madasamy, P., Honkanen, S., Kippelen, B., Peyghambarian, N., Marder, S. R., Jen, A. K., & Wu, J. (2000). Poling of soda-lime glass for hybrid glass/polymer electro-optic modulators. Applied Physics Letters, 76(9), 1086-1088.
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  Abstract: We report on a poling process of soda-lime glasses that reduces their surface conductivity by five orders of magnitude. We show that this process enables the in-plane poling of high Tg (180 °C) electro-optic (EO) polymers coated on ion-exchanged channel waveguides fabricated in soda-lime glasses for hybrid modulators. © 2000 American Institute of Physics.
• Ferrio, K. B., Herlocker, J. A., Hendrickx, E., Wang, J. F., Zhang, Y., Persoons, A. P., Peyghambarian, N., & Kippelen, B. (2000). Stabilized response-time in a photorefractive polymer composite doped with a styrene chromophore and C₆₀. Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest, 9-.
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  Abstract: Measurements were carried out to determine what accompanies the build-up of C60-. It was observed that build-up is accompanied by large increase in the response-time of index-modulation in transient-grating experiments. This observation indicates that the response-time may be stabilized by increasing the chromophore ionization potential (IP).
• Geraghty, D. F., Provenzano, D., Morrell, M. M., Ingenhoff, J., Drapp, B., Honkanen, S., Yariv, A., & Peyghambarian, N. (2000). Polarisation-independent Bragg gratings in ion-exchanged glass channel waveguides. Electronics Letters, 36(6), 531-532.
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  Abstract: The polarisation dependence of Bragg gratings photowritten in ion-exchanged glass waveguides is characterised for waveguides with different mask-opening widths and burial depths. It is found that polarisation-independent gratings can be written in waveguides with a wide variation in fabrication parameters.
• Geraghty, D. F., Äyräs, P., Jabbour, G. E., Honkanen, S., & Peyghambarian, N. (2000). Self-aligned photoresist patterning for integrated optics. Optical Engineering, 39(2), 575-576.
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  Abstract: A novel technique that provides self-alignment in the photoresist exposure step of the photolithography process is presented. In this procedure, the mode of the waveguide itself defines the intensity pattern that exposes the photoresist. The technique could be used to define the active area for an organic LED and achieve the integration of an organic LED with optical waveguide, a grating, and a detector to simulate the operation and structure of a multifunctional broadband integrated sensor element based on an organic-inorganic structure.
• Golemme, A., Kippelen, B., & Peyghambarian, N. (2000). On the mechanism of orientational photorefractivity in polymer dispersed nematics. Chemical Physics Letters, 319(5-6), 655-660.
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  Abstract: An unusual dependence of the diffraction efficiency on the applied electric field was observed in four-wave mixing experiments on polymer dispersed nematics. The data were interpreted on the basis of a simple model which considers the orientational nature of the photorefractivity in liquid crystalline materials. Such model should also be of relevance for any material with orientational contributions to photorefractivity.
• Hendrickx, E., Kippelen, B., Thayumanavan, S., Marder, S. R., Persoons, A. P., & Peyghambarian, N. (2000). Improved photogeneration efficiency of charge-transfer complexes between C₆₀ and low ionization potential arylamines. Molecular Crystals and Liquid Crystals Science and Technology Section B: Nonlinear Optics, 25(1-4), 303-308.
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  Abstract: Photogeneration of charge carriers was measured at 633 nm in a series of polymer composites based on polystyrene, doped with a triphenyldiamine derivative as hole transport molecule and C60 as sensitizer. Light absorption and generation of mobile carriers was achieved through the charge-transfer (CT) complex formed between the hole transport molecule and the sensitizer. We discuss the influence of the ionization potential of the hole-transport molecule on the photogeneration efficiency of the CT complex it forms with the sensitizer C60. In one composite we have found a photogeneration efficiency of unity at an applied electric field of 55 V/μm.
• Hendrickx, E., Kippelen, B., Thayumanavan, S., Marder, S. R., Persoons, A., & Peyghambarian, N. (2000). High photogeneration efficiency of charge-transfer complexes formed between low ionization potential arylamines and C₆₀. Journal of Chemical Physics, 112(21), 9557-9561.
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  Abstract: The photogeneration efficiencies of a series of arylamine derivatives with different redox properties, each doped in a polystyrene matrix and sensitized with C60 and 633 nm were measured. It was found that the photogeneration efficiency correlates with the donor molecule Ip concentration. Particularly in one composite, the photogeneration efficiency reached its theoretical limit of 100% at applied fields as low as 55 V/μm.
• Herlocker, J. A., Fuentes-Hernandez, C., Ferrio, K. B., Hendrickx, E., Blanche, P. -., Peyghambarian, N., Kippelen, B., Zhang, Y., Wang, J. F., & Marder, S. R. (2000). Stabilization of the response time in photorefractive polymers. Applied Physics Letters, 77(15), 2292-2294.
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  Abstract: The optical and photoconductive fatigue of fast photorefractive polymers have been studied in a family of C60-sensitized polymer composites containing styrene-based chromophores with varying ionization potential. Changes in response time and in photoconductivity were studied for exposures up to 104 J/cm2. Increasing the chromophore ionization potential beyond that of the polyvinylcarbazole host was found to stabilize the response time. Studies of the electric-field dependence of the steady-state diffraction efficiency in various samples confirm the role of C60 anions as possible traps. © 2000 American Institute of Physics.
• Hwang, B., Jiang, S., Luo, T., Watson, J., Sorbello, G., & Peyghambarian, N. (2000). Cooperative upconversion and energy transfer of new high Er³⁺- and Yb³⁺-Er³⁺-doped phosphate glasses. Journal of the Optical Society of America B: Optical Physics, 17(5), 833-839.
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  Abstract: Systematic studies of cooperative upconversion and Yb3+-Er 3+ energy transfer in newly developed phosphate glasses were performed by a rate-equation formalism. The cooperative-upconversion coefficients of the 4I13/12 level for different Er 3+ concentrations were determined from the luminescence-decay curves for high pump intensities. A small cooperative-upconversion coefficient of 1.1 × 10-18cm3/s was obtained for a high Er 3+ concentration of 4 × 1020 ions/cm3. Yb3+-Er3+ energy-transfer coefficients for an Er 3+ concentration of 2 × 1020 ions/cm3 codoped with different Yb3+ concentrations were calculated from the lifetime measurements of the 2F5/2 level of Yb 3+ ions. For Er3+ codoped with an Yb3+ concentration of 6 × 1020 ions/cm3, an energy-transfer coefficient of 1.1 × 10-16 cm3/s and an energy-transfer efficiency higher than 95% were determined from our measurements under weak excitation. The cooperative-upconversion coefficients of Yb3+-Er3+-doped samples were found to be consistent with that of an Er3+-doped sample with the same Er3+ concentration. The weak cooperative-upconversion effect of high Er3+ concentrations and efficient Yb3+-Er3+ energy transfer indicate that these newly developed Er3+- and Yb3+-Er 3+-doped phosphate glasses are excellent for active device applications. © 2000 Optical Society of America.
• Jiang, S., Hwang, B., Luo, T., Seneschal, K., Smektala, F., Honkanen, S., Lucas, J., & Peyghambarian, N. (2000). Net gain of 15.5 dB from a 5.1 cm-long Er³⁺-doped phosphate glass fiber. Conference on Optical Fiber Communication, Technical Digest Series, 4, 181-183.
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  Abstract: New erbium-doped phosphate glasses and fibers were fabricated. A net gain of 15.5dB at 1535nm was achieved from a 5.1cm-long fiber, which represents the highest gain per unit length for fiber amplifiers to the best of our knowledge.
• Jiang, S., Luo, T., Hwang, B., Smekatala, F., Seneschal, K., Lucas, J., & Peyghambarian, N. (2000). Er³⁺-doped phosphate glasses for fiber amplifiers with high gain per unit length. Journal of Non-Crystalline Solids, 263, 364-368.
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  Abstract: The effect of the types of alkaline earth metal ions (Mg2+, Ca2+ and Ba2+) and concentration of Al2O3 and BaO on the refractive index and the effective emission linewidths of the 4I13/2 - 4I15/2 transition of Er3+ ions in phosphate glasses, 64P2O5 · 12Al2O3 · 3.5(Er2O3 + La2O3) · 20.5MO (M = Mg, Ca, Ba) and 64P2O5 · 3.5(Er2O3 + La2O3) · (21.5 - x)Al2O3 · (11 + x)BaO (x = 0, 3.5, 6.5 and 9.5), were investigated. A single mode Er3+ doped phosphate glass fiber with a core diameter of 4 μm was fabricated by the rod-in-tube technique. A new Er3+ doped fiber amplifier is demonstrated pumping with a 980 nm fiber pigtailed-laser diode. A gain per unit length greater than 2 dB/cm is demonstrated, which is the largest gain per unit length for fiber amplifiers to our knowledge.
• Kadono, K., Porque, J., Hwang, B., Jiang, S., Yazawa, T., & Peyghambarian, N. (2000). Rate equation analyses and energy transfer of Er³⁺-doped sulfide glasses. Proceedings of SPIE - The International Society for Optical Engineering, 3942, 14-20.
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  Abstract: Decay curves of 1.5 μm (4I13/2) and 980 nm (4I11/2) emissions from Er3+ ions in Ga2S3-GeS2-La2S3 glasses were measured by the excitation of 1.5 μm laser diode pump. The decay curves were simulated using rate equations for a model consisting of four levels (4I15/2, 4I13/2, 4I11/2, and 4I9/2) of Er3+. A pair of unknown parameters, i.e., an excited state absorption coefficients for 4I13/2→4I9/2, σesa, and a cooperative upconversion coefficient for (4I13/2, 4I15/2)→(4I9/2, 4I15/2), C, were included in the rate equations. They were estimated by fitting the simulated curves to the measured ones. The obtained values were 3×10-21 cm2 and 1 or 3×10-21 cm3/s for the σesa and C, respectively.
• Mathine, D. L., Woo, H. S., He, W., Kim, T. W., Kippelen, B., & Peyghambarian, N. (2000). Heterogeneously integrated organic light-emitting diodes with complementary metal-oxide-silicon circuitry. Applied Physics Letters, 76(26), 3849-3851.
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  Abstract: Top-emitting arrays of organic light-emitting diodes (OLEDs) have been fabricated and demonstrated on complementary metal-oxide-silicon (CMOS) circuitry. The 8 × 8 array of OLEDs is composed of 90 μm micropixels with a 55 μm separation. The OLEDs are based on an emitting layer of tris-(8-hydroxyquinoline)aluminum (Alq3) doped with coumarin 6 to provide green light emission. A layer of N,N′-diphenyl-N, N′-bis(3-methylphenyl)1-1′-biphenyl 1-4, 4′-diamine (TPD) was used as a hole transport layer and poly(ethylenedioxythiophene) doped with polystyrenesulfonate was used as a buffer layer between the TPD and the CMOS anode metal. Bright light was emitted through a semitransparent Mg:Ag cathode when the micropixel was driven by an individual current source. © 2000 American Institute of Physics.
• Pardo, D. A., Jabbour, G. E., & Peyghambarian, N. (2000). Application of screen printing in the fabrication of organic light-emitting devices. Advanced Materials, 12(17), 1249-1252.
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  Abstract: Screen printing (SP) is a simple, versatile, fast, and cost-effective method of fabricating organic light-emitting devices, allowing the deposition of organic layers with less than 100 nm film thickness. SP can be a valuable tool in the fabrication of logos and low information-content displays.
• Porque, J., Jiang, S., Hwang, B., Fuflyigin, V., Salley, E., Zhao, J., & Peyghambarian, N. (2000). Fluorescence properties of erbium doped germanate glasses. Proceedings of SPIE - The International Society for Optical Engineering, 3942, 60-67.
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  Abstract: Two erbium doped germanate glass samples prepared by sol-gel process and melting and casting method, respectively, have been characterized. A fluorescence lifetime of 2.5 ms at the 4I13/2 level and a very broad bandwidth (FWHM: 53.7 nm) around 1.55 μm have been observed for the sol-gel sample. The fluorescence lifetime and the spectrum bandwidth for 1.535 μm transition for the sample fabricated by the melting and casting technique were measured to be 10 ms, and 19 nm (FWHM). The cooperative up-conversion coefficient is measured to be 1.3×1018 cm3/s for the sample with an erbium concentration of 2.69×1020 ions/cm3.
• Ramos-Ortiz, G., Spiegelberg, C., Peyghambarian, N., & Kippelen, B. (2000). Temperature dependence of the laser emission threshold in organic semiconductor lasers. Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest, 112-113.
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  Abstract: The temperature dependence of whispering gallery mode microring lasers using the conjugated polymer BEH:PPV as a gain medium was studied. In this case the threshold for laser emission is controlled by the gain coefficient. Based on the four level system, lowering the temperature in the gain medium should increase the population inversion, increase the gain and decrease the laser emission threshold. The laser structure were obtained by etching optical fibers with hydrofluoric acid and dipping them in xylene solution.
• Ramos-Ortiz, G., Spiegelberg, C., Peyghambarian, N., & Kippelen, B. (2000). Temperature dependence of the threshold for laser emission in polymer microlasers. Applied Physics Letters, 77(18), 2783-2785.
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  Abstract: We studied the temperature dependence of the laser emission threshold in microring polymer lasers. For microring lasers with diameters between 16 and 120 μm, a weak temperature dependence was observed when the temperature was varied between 300 and 10 K. These experimental results are explained within a four-level model. Our results suggest that a significant reduction of threshold can be achieved at low temperatures if the quality factor Q of the microcavities is improved. © 2000 American Institute of Physics.
• Ramponi, R., Osellame, R., Marangoni, M., Sorbello, G., Laporta, P., Jiang, S., Hu, Y., & Peyghambarian, N. (2000). New Er-doped phosphate glass for ion-exchange active waveguides: accurate determination of the refractive index. Optical Materials, 14(4), 291-296.
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  Abstract: The optical properties of a new Er-doped glass for ion-exchange active waveguides have been characterized, including fluorescence lifetime, Ag-Na diffusion coefficient, and refractive index. In particular, the Sellmeier curve was determined from the visible to the near infrared by means of a non-conventional method based on the measurement of the output angle of radiation modes propagating within the substrate. An accuracy of about 1 × 10-4 for the determination of the refractive index is obtained.
• Sorbello, G., Taccheo, S., Marangoni, M., Osellame, R., Ramponi, R., Laporta, P., Svelto, O., Jiang, S., Hu, Y., Seneschal, K., Peyghambarian, N., Fusari, F., Brioschi, L., Ungaro, G., Chiaretti, G., & Lenzi, M. (2000). Buried-channel active waveguide array on Er:Yb:phosphate glass by field-assisted ion-exchange technique. Conference on Lasers and Electro-Optics Europe - Technical Digest, 314-.
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  Abstract: The fabrication procedures and optical characterization of an active buried-channel waveguide array fabricated on a special erbium-ytterbium doped phosphate glass are presented by the ion-exchange technique. A new glass composition optimized for Ag-Na exchange with custom Er and Yb concentrations chosen on the basis of the results of a numerical code. The waveguides are fabricated by means of a double-step Ag-Na ion exchange process.
• Wundke, K., Pötting, S., Auxier, J., Schülzgen, A., Peyghambarian, N., & Borrelli, N. F. (2000). PbS quantum-dot-doped glasses for ultrashort-pulse generation. Applied Physics Letters, 76(1), 10-12.
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  Abstract: We investigate the use of PbS quantum-dot-doped glasses as saturable absorbers for ultrashort-pulse lasers by means of absorption bleaching experiments and numerical analysis of the pulse shaping process using the Haus' master equation. We explain the mode-locking mechanism and the limitations of these absorbers. The generation of transform-limited fs pulses is predicted by soliton mode locking initiated by the absorption saturation of higher excited states of the quantum-dot saturable absorber. © 2000 American Institute of Physics.
• Ayras, P., Conti, G., Honkanen, S., & Peyghambarian, N. (1999). Birefringence control for ion-exchanged channel waveguides at 1.55 μm wavelength. Proceedings of SPIE - The International Society for Optical Engineering, 3620, 233-239.
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  Abstract: We show at 1.55 μm wavelength that the waveguide birefringence of ion-exchanged channel waveguides in glass can be broadly tuned by a potassium and silver double-ion-exchange. Two different potassium and silver double-ion-exchange processes are used to make surface waveguides with negligible waveguide birefringence. This is of crucial importance in making devices for dense wavelength division multiplexing (DWDM) systems. The dependence of the waveguide birefringence on the channel width is also reported.
• Ayras, P., Geraghty, D. F., Honkanen, S., Grace, K. M., Swanson, B., Shrouf, K., Yang, X., Katila, P., Leppihalme, M., Tervonen, A., & Peyghambarian, N. (1999). Thin film waveguide sensors for chemical detection. Proceedings of SPIE - The International Society for Optical Engineering, 3537, 310-316.
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  Abstract: Chemical sensor scheme based on selective sensing surfaces and highly sensitive integrated optical transduction is presented. Self-assembly techniques are used to covalently attach species selective films onto the surface of silicon nitride waveguides. Exposure to targeted analytes results in selective absorption of these molecules onto the waveguide surface causing a change in the effective refractive index of the guided modes. These relative changes in effective refractive indices of TM and TE modes are using Zeeman interferometry. The measurements demonstrate reversible, real-time sensing of volatile organic compounds at ppm level. Improvements in the waveguide design are proposed to further increase the sensor performance.
• Bellmann, E., Shaheen, S. E., Grubbs, R. H., Marder, S. R., Kippelen, B., & Peyghambarian, N. (1999). Organic two-layer light-emitting diodes based on high-T_g hole-transporting polymers with different redox potentials. Chemistry of Materials, 11(2), 399-407.
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  Abstract: A series of soluble arylamine-based hole-transporting polymers with glass transition temperatures in the range of 130-150°C have been synthesized. The synthetic methodology allows facile substitution of the aryl groups on the amine with electron-withdrawing and electron-donating moieties, which permits tuning of the redox potential of the polymer. These polymers have been used as hole-transport layers (HTLs) in two-layer light-emitting diodes ITO/HTL/Alq/Mg [ITO = indium tin oxide, Alq = tris(8-quinolinato)aluminum]. The maximum external quantum efficiency of the device increases if the redox potential of the HTL is increased to facilitate reduction of the positive charge carriers at the HTL/Alq interface. A fluorinated hole-transport polymer with a relatively large redox potential (390 mV vs ferrocenium/ferrocene) yielded the device with the highest external quantum efficiency of 1.25% photons/e-. The device stability, however, follows the opposite trend. The device with the most electron-rich HTL exhibited the best performance after prolonged usage. © 1999 American Chemical Society.
• Conti, G., Ayras, P., Cavaliere, C., Hwang, B. C., Luo, T., Rantala, J. T., Jiang, S., Honkanen, S., & Peyghambarian, N. (1999). Strip-loaded structure for ion-exchanged Er³⁺-doped glass waveguide amplifiers. Proceedings of SPIE - The International Society for Optical Engineering, 3622, 122-128.
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  Abstract: A new strip-loaded structure for ion-exchanged waveguide amplifiers in Er3+-doped glass is suggested. The fabrication of these waveguides lacks steps such as mask deposition and burial process that can be critical for some glasses. A simple numerical modeling shows that similar, or even higher, gain values as in ion-exchanged buried waveguides can be achieved. Preliminary experimental data for the fabrication of the strip-loaded structure are also reported.
• Ding, Y., Jiang, S., Luo, T., Hu, H., Miura, Y., & Peyghambarian, N. (1999). Lithium disilicate crystalline slab waveguides from surface crystallised glass. Electronics Letters, 35(6), 504-505.
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  Abstract: Crystalline slab waveguides of lithium disilicate (Li2Si2O5) were prepared by surface crystallisation of a lithium disilicate glass after heat treatment. By controlling the depth of the waveguides with varying heat treatment temperatures and times, singlemode and multimode waveguides were obtained. The refractive index and optical propagation loss of the slab waveguides were characterised.
• Geraghty, D. F., Provenzano, D., Marshall, W. K., Honkanen, S., Yariv, A., & Peyghambarian, N. (1999). Gratings photowritten in ion-exchanged glass channel waveguides. Electronics Letters, 35(7), 585-587.
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  Abstract: Gratings photowritten in commercial ion exchanged glass channel waveguides are demonstrated. The transmission of the waveguides is analyzed, the polarization dependence characterized, and avenues for future improvements are discussed. The method allow for low-loss, polarization insensitive gratings to be written in either surface or buried ion-exchanged glass channel waveguides.
• Giessen, H., Butty, J., Woggon, U., Fluegel, B., Mohs, G., Hu, Y. Z., Koch, S. W., & Peyghambarian, N. (1999). Ultrafast nonlinear gain dynamics in semiconductor nanocrystals. Phase Transitions, 68(1), 59-94.
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  Abstract: II-VI semiconductor (CdS, CdSe) nanocrystals with an average size of approximately one bulk exciton Bohr radius are embedded in a glass matrix. Due to the quantum confinement effect, they act as a quasi zero-dimensional system (quantum dots). Under strong nanosecond and femtosecond optical excitation, these quantum dots exhibit optical amplification (gain). We investigate the ultrashort gain dynamics of the strongly confined CdSe quantum dots by femtosecond pump-probe spectroscopy. From multiple-beam pump-probe measurements, we conclude that the gain mechanism is governed by biexciton to exciton transitions. Femtosecond dephasing measurements reveal a constant scattering rate across the gain region and confirm the two-electron-hole pair gain model. Nanosecond pump-probe measurements on CdS quantum dots in sol-gel glasses show optical gain up to room temperature. In all cases, the gain region is broad and stretches below the fundamental absorption of the nanocrystals. The reason is the multitude of transitions involved in the gain formation. No phonon bottleneck did prevent any quick relaxation or any fast scattering that would replenish the spectral holes in the gain region. The relaxation rates are on the order of 10 ps. The luminescence decay time is nonexponential with a 40-100 ps component for the stimulated emission.
• Hendrickx, E., Guenther, B. D., Zhang, Y., Wang, J. F., Staub, K., Zhang, Q., Marder, S. R., Kippelen, B., & Peyghambarian, N. (1999). Ellipsometric determination of the electric-field-induced birefringence of photorefractive dyes in a liquid carbazole derivative. Chemical Physics, 245(1-3), 407-415.
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  Abstract: We have used ellipsometric measurements on solutions of 2-dihexylamino-7-dicyanomethylidene-3,4,4a,5,6-pentahydronaphthalene and related polyenes in liquid 9-(2′-ethylhexyl)carbazole to measure the electric-field-induced birefringence at wavelengths of 690 nm and 830 nm. This electric-field-induced birefringence is related to the product of dipole moment squared and the polarizability anisotropy, μ2Δα, and to a large extent determines the dye's photorefractive figure-of-merit (FOM). We show that μ2Δα increases with the conjugation length and report one of the highest μ2Δα values observed so far.
• Herlocker, J. A., Ferrio, K. B., Hendrickx, E., Guenther, B. D., Mery, S., Kippelen, B., & Peyghambarian, N. (1999). Direct observation of orientation limit in a fast photorefractive polymer composite. Applied Physics Letters, 74(16), 2253-2255.
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  Abstract: The photorefractivity and chromophore orientation in polymer composites were studied. The composites were made from poly-N-vinylcarbazole, N-ethylcarbazole, and (2,4,7-trinitro-9-fluorenylidene)malonodinitrile with a fluorinated cyano-tolane chromophore. The transient photorefractive response in four-wave mixing (FWM) and two-beam coupling (TBC) was measured. Transient FWM revealed a photorefractive response dominated by a fast time constant of 4 ms, while transient ellipsometry revealed an orientational response of only 490 μs.
• Herlocker, J. A., Ferrio, K. B., Hendrickx, E., Guenther, B. D., Mery, S., Kippelen, B., & Peyghambarian, N. (1999). Observation of 4-ms response-time in a photorefractive polymer. Proceedings of SPIE - The International Society for Optical Engineering, 3623, 168-174.
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  Abstract: Efficient photorefractive polymers hold great potential for optical data processing and storage and so have been a topic of intense investigations in recent years. Materials with nearly 100% diffraction efficiencies have been developed, but these have been generally characterized by much slower responses than their less efficient inorganic counterparts. In this report, we describe a 4-ms initial rise-time using a visible-transparent chromophore in a PVK-based polymer of Tg = 39°C for 48-V/μm bias projected along the grating vector and 250-m W/cm2 writing beams. This fast component consistently accounts for 90% of the steady-state response and is analyzed as a function of bias field. We also present transient ellipsometry measurements of an orientational response significantly faster than the grating development, suggesting that chromophore alignment speed does not limit transient grating formation. We describe the role of such underlying property measurements in understanding photorefractive transient behavior, and prospects for further improvements.
• Herman, G. S., Barnes, N. P., & Peyghambarian, N. (1999). Narrow-band and wide-band coherent terahertz source generation using 3 wave difference frequency mixing and Cross-Reststrahlen-band dispersion compensation in ultra-high purity III-V semiconductor crystals. Proceedings of SPIE - The International Society for Optical Engineering, 3617, 112-123.
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  Abstract: We discuss the Cross-Reststrahlen band phasematching technique for narrow-band three-wave interactions. In GaP, assuming a maximum practical crystal length of 100 millimeters, the calculations predict that with a source wavelength of 0.965 micrometers, a tuning range of greater than 50 GHz is possible around the perfectly phasematched 3.0 THz center frequency. When GaP is pumped with a source wavelength of 1.000 micrometers, the coherence length is at least 100 mm for a frequency range of greater than 600 GHz around the perfectly phasematched 630 GHz center frequency. High Resistivity GaP is available in cylindrical boules that are larger than 50 millimeters in diameter and 75 millimeters in length. GaP has a bandgap cutoff wavelength in the Visible at 0.55 micrometers and a simple phonon absorption spectrum with a single fundamental absorption at approximately 27 micrometers (11 THz), which indicates a potential for high transmission in both the NIR and FIR. Any remaining FIR absorption can be attributed to free electron absorption and two phonon absorption processes. In this paper, we report new measurements of GaP regarding FIR absorption, optical damage threshold and optical quality. These measurements indicate that undoped, high-resistivity GaP single crystal can be used to generate THz waves.
• Hwang, B. C., Jiang, S., Luo, T., Watson, J., Honkanen, S., Hu, Y., Smektala, F., Lucas, J., & Peyghambarian, N. (1999). Erbium-doped phosphate glass fibre amplifiers with gain per unit length of 2.1 dB/cm. Electronics Letters, 35(12), 1007-1009.
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  Abstract: Singlemode high erbium-doped phosphate glass fibres have been designed and fabricated. Gain measurements in a 2.15 cm fibre with an Er3+ concentration of 3.7×1020 cm-3 were performed. A net gain of 2.1 dB/cm at 1537 nm was demonstrated with a pump diode power of 110 mW at 980 nm.
• Hwang, B., Jiang, S., Luo, T., Neindre, L. L., Watson, J., & Peyghambarian, N. (1999). Characterization of cooperative upconversion and energy transfer of Er³⁺ and Yb³⁺/Er³⁺ doped phosphate glasses. Proceedings of SPIE - The International Society for Optical Engineering, 3622, 10-18.
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  Abstract: Cooperative upconversion and Yb3+-Er3+ energy transfer in newly developed phosphate glasses were studied in this paper. The cooperative upconversion coefficients of 4I13/2 level for different Er3+ concentrations were deduced from the pump intensity-dependent luminescence decay curves. Yb3+-Er3+ energy transfer efficiencies for different Yb3+ concentrations codoped with Er3+ (approximately 2×1020 ions/cm3) were estimated from the lifetime measurements of 2F5/2 level of Yb3+ ions. The small cooperative upconversion coefficients and high Yb3+-E3+ energy transfer efficiencies indicate these newly developed Er3+ and Yb3+/Er3+ doped phosphate glasses are excellent for amplifier and laser applications.
• Jabbour, G. E., Wang, J., Kippelen, B., & Peyghambarian, N. (1999). Sharp red organic light-emitting devices with enhanced efficiency. Japanese Journal of Applied Physics, Part 2: Letters, 38(12 B), L1553-L1555.
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  Abstract: The fabrication of efficient and bright red light-emitting organic electroluminescent devices based on Eu-complex, having narrow spectral width, is achieved by enhancing the electron injection process through the use of LiF/Mg cathode. Devices with external quantum efficiency exceeding 1% and light output higher than 320 cd/m2 are presented. While the external quantum efficiency at 100 cd/m2 is comparable, the luminous efficiency is 2.6 times higher than that of the recent state-of-the-art devices based on the phosphorescent dye PtOEP.
• Kelly, D., Grace, K. M., Song, X., Swanson, B. I., Frayer, D., Mendes, S. B., & Peyghambarian, N. (1999). Integrated optical biosensor for detection of multivalent proteins. Optics Letters, 24(23), 1723-1725.
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  PMID: 18079915;Abstract: We have developed a simple, highly sensitive and specific optical waveguide sensor for the detection of multivalent proteins. The optical biosensor is based on optically tagged glycolipid receptors embedded within a fluid phospholipid bilayer membrane formed upon the surface of a planar optical waveguide. Binding of multivalent cholera toxin triggers a fluorescence resonance energy transfer that results in a two-color optical change that is monitored by measurement of emitted luminescence above the waveguide surface. The sensor approach is highly sensitive and specific and requires no additional reagents and washing steps. Demonstration of protein-receptor recognition by use of planar optical waveguides provides a path forward for the development of fieldable miniaturized biosensor arrays. © 1999 Optical Society of America.
• Kippelen, B., Golemme, A., Hendrickx, E., Wang, J. F., Marder, S. R., & Peyghambarian, N. (1999). Photorefractive polymers and polymer-dispersed liquid crystals. ACS Symposium Series, 726, 204-225.
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  Abstract: Photorefractive (PR) polymers are multifunctional field-responsive materials that combine photoconducting and electro-optic properties. In this chapter, we will review the basics of photorefractivity in polymers and liquid crystals and describe recent advances that have led to highly efficient materials. These advances in material development enable a variety of photonic applications including optical correlators for security verification.
• Luo, T., Jiang, S., Yongdan, H. u., Conti, G. N., Honkanen, S., Mendes, S. B., & Peyghambarian, N. (1999). Germanate glass channel waveguides for infrared waveguide lasers. IQEC, International Quantum Electronics Conference Proceedings, 266-.
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  Abstract: A germanate glass channel waveguide was designed and fabricated for infrared waveguide lasers. The germanate glass contained GeO2, Al2O3Na2O3, BaO and rare-earth ions and was developed into waveguide by the molten salt ion-exchange technique. The germanate glass is a major step forward to realize 2 μm integrated waveguide lasers.
• Mathine, D. L., Woo, H. S., He, W., Kim, T. W., Kippelen, B., & Peyghambarian, N. (1999). Organic LEDs heterogeneously integrated with CMOS circuitry. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 1, 216-217.
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  Abstract: The integration of organic light-emitting diodes (OLED) with custom CMOS circuitry for active display applications was investigated. Initial development is the integration of OLEDs on CMOS circuitry was performed on metallized silicon substrates. The CMOS integration proceeded with a custom design that was fabricated through the MOSIS service in a 0.8 μm technology. The integrated OLEDs were measured by driving the input to the modified current mirror. The input voltage corresponds to the input voltage of the modified current mirror.
• Murray, J. T., Austin, W. L., Powell, R. C., & Peyghambarian, N. (1999). Theory of Raman gain spectrum transformations. Optical Materials, 11(4), 373-382.
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  Abstract: A theory describing the spectral characteristics of Raman lasers is presented. The foundation of the theory is anchored in the probabilistic nature of light-matter interactions. The Raman gain spectrum is predicted for the cases when the pump laser is oscillating in both a single longitudinal mode and multi-longitudinal mode configuration. The gain profile predicted in the two previous cases are shown to be equivalent to homogeneously and inhomogeneously broadened laser transitions, respectively. This theory is necessary to predict the behavior of Raman lasers when injection-seeding, mode-locking, or multi-frequency operation is desired. Detailed calculations are performed for the case where the pump laser medium in Nd:YAG and the Raman medium is Ba(NO3)2. © 1999 Elsevier Science B.V. All rights reserved.
• Neindre, L. L., Jiang, S., Hwang, B., Luo, T., Watson, J., & Peyghambarian, N. (1999). Effect of relative alkali content on absorption linewidth in erbium-doped tellurite glasses. Journal of Non-Crystalline Solids, 255(1), 97-102.
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  Abstract: Er3+ doped tellurite glasses with various Na2O/Li2O, Na2O/K2O and K2O/Li2O ratios (0-4.5) were prepared at 850°C using a platinum crucible. The effect of relative alkali content on absorption linewidth in erbium-doped tellurite glasses was investigated. The highest effective linewidth was obtained from glass samples with mixed alkali molar ratio of Na2O/Li2O = 1, Na2O/K2O = 1 and K2O/Li2O = 1. Glass transition temperature, crystallization temperature, density, refractive index, Judd-Ofelt parameters and emission cross-section of Er3+ doped tellurite glasses are also reported.
• Neindre, L. L., Luo, T., Hwang, B., Watson, J., Jiang, S., & Peyghambarian, N. (1999). Erbium-doped tellurite glasses for 1.5 μm broadband amplification. Proceedings of SPIE - The International Society for Optical Engineering, 3622, 58-65.
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  Abstract: Er3+ doped tellurite glasses with various Na2O/Li2O, Na2O/K2O and K2O/Li2O ratios were prepared. Absorption and emission spectra, glass transition temperatures, crystallization temperatures, densities, and refractive index of these glass samples were characterized. For all studied glass samples, the highest effective linewidth was obtained with mixed alkali molar ratio of Na2O/Li2O = 1, Na2O/K2O = 1 and K2O/Li2O = 1. The studied glasses have a (Tx-Tg) exceeding 100 °C, indicating these glass samples are stable against devitrification. In addition, Judd-Ofelt analysis of several glasses was also performed.
• Peyghambarian, N., Ferrio, K. B., Herlocker, J. A., Hendrickx, E., Guenther, B. D., Kippelen, B., & Mery, S. (1999). Photorefractive polymers with video-rate performance. Proceedings of SPIE - The International Society for Optical Engineering, 3749, 336-337.
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  Abstract: The introduction of birefringent chromophores with ground-state dipole moments into a photoconductive polymer host has provided the design flexibility to improve both dynamic range and speed. From the diffraction efficiency and Kogelnik's theory of thick gratings, it exhibits a dominant response time of approximately 2 ms for the underlying index-modulation with an additional slow component of approximately 1 ms and may support applications requiring video-rates. The orientational mobility of the chromophores is not limiting the response of the composite and kiloherts-regime responses may be achievable with improved photoconductivity.
• Peyghambarian, N., Ferrio, K. B., Herlocker, J. A., Hendrickx, E., Guenther, B. D., Mery, S., Zhang, Y., & Kippelen, B. (1999). Photorefractive polymers with high speed. Materials Research Society Symposium - Proceedings, 561, 131-139.
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  Abstract: Rapid progress in photorefractive polymers includes new materials with improved response rates. We briefly review recent developments in this rapidly evolving area and report grating formation with a 2-millisecond time-constant, the fastest reported to date in any photorefractive polymer.
• Peyghambarian, N., Skrdla, P. J., Saavedra, S. S., Armstrong, N. R., Mendes, S. B., & Peyghambarian, N. N. (1999). Sol-gel-based, planar waveguide sensor for water vapor. Analytical chemistry, 71(7).
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  A water vapor sensor based on a combination of sol-gel processing and planar optical waveguide technologies has been developed. The indicator erythrosin B was entrapped in a thin sol-gel film (thickness ∼100 nm) prepared from methyltriethoxysilane, dimethyldiethoxysilane, and tetraethoxysilane. This dye exhibits an increase in absorbance in the presence of liquid or gaseous water. The sol-gel layer containing the dye was deposited onto a sol-gel-derived, single-mode planar waveguide. Outcoupled light intensity measurements (at 514.5 nm) over a range of water vapor concentrations (in a nitrogen gas stream) yielded a response over a wide range of relative humidity (
• Provenzano, D., Marshall, W. K., Yariv, A., Geraghty, D. F., Honkanen, S., & Peyghambarian, N. (1999). Grating formation in BGG31 glass by UV exposure. Electronics Letters, 35(16), 1332-1334.
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  Abstract: A three-dimensional index variation grating in bulk BGG31 glass written using neither hydrogen loading nor germanium doping is demonstrated. This material is useful for fabricating ion-exchanged waveguides, and its photosensitivity to ultraviolet (UV) radiation at 248nm has not been previously explored. Intensity measurements of the Bragg diffracted spots indicated a maximum index variation (Δn) of approx. 4 × 10-5.
• Rantala, J. T., Ayras, P., Levy, R., Descour, M. R., Honkanen, S., & Peyghambarian, N. (1999). Fabrication of hybrid sol-gel glass diffractive elements. Proceedings of SPIE - The International Society for Optical Engineering, 3620, 212-218.
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  Abstract: Organically modified photosensitive hybrid glasses are synthesized and used for the fabrication of diffractive optical elements. The material synthesis is based on a sol-gel process. The materials are spin-deposited onto glass substrates that also have a significant role in the component assembly. The synthesised material has a negative tone property under UV-radiation and they can be patterned by a conventional UV-lithography process. Binary diffractive lenses are photoimprinted through an amplitude contact mask. Optical properties and surface roughness of the materials and elements are evaluated. Diffraction efficiencies of the elements are also measured. The process and material optimization for the reliable fabrication of integrated optics devices is carried out.
• Rantala, J. T., Honkanen, S., & Peyghambarian, N. (1999). Potential and challenges of sol-gel materials for erbium-doped amplifiers. Proceedings of SPIE - The International Society for Optical Engineering, 3622, 52-57.
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  Abstract: Sol-gel materials have been widely used for the fabrication of micro-optical devices during the last decade. Motivation for the sol-gel processing has been the low cost and a large variety of fabrication techniques and material properties. One of the interesting possibilities has been to use sol-gel glasses as an erbium host for integrated optics amplifiers. Several research results have been published, but sol-gel processing has not yet proven its potential for efficient devices in this important and rapidly advancing field. There are still some problems to be solved, such as the removal of residual water from sol-gel matrices and the process reliability and reproducibility. In this paper, we review the present status of the sol-gel materials and discuss their potential and challenges for the erbium-doped waveguide amplifiers.
• Spiegelberg, C., Peyghambarian, N., & Kippelen, B. (1999). Temperature dependence of the stimulated emission in a conjugated polymer. Applied Physics Letters, 75(6), 748-750.
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  Abstract: Photoluminescence and stimulated emission measurements on poly(2,5-bis(2′-ethylhexyloxy)-1,4-phenylenevinylene) show only a slight thermal-dependence on the threshold for spectral line narrowing. Done between 15 and 300 K, the measurements showed a decrease in threshold intensity at lower temperatures, which can be mainly attributed to an increase in quantum efficiency. This deviation from the expected behavior for a four-level system is assigned to the dominant inhomogeneous broadening.
• Wang, Q., Weijin, L. i., Jabbour, G. E., Cui, J., Marks, T. J., Kippelen, B., & Peyghambarian, N. (1999). Micro-contact printing approaches to organic light-emitting diode pixels. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 40(2), 1248-1249.
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  Abstract: A new method to organic light emitting diodes (OLED) pixel fabrication using micro-contact printing is reported. The current-voltage and brightness-voltage for the octadecyltrichlorosilane (OTS) covered areas turn on at 12 V and 16.75 V, respectively. These pixels have an average brightness, which is sufficient for display applications. This procedure is essentially compatible with all of the methods to make OLEDs such as thermal evaporation, spin coating, and self assembly.
• Wundke, K., Auxier, J., Schülzgen, A., Peyghambarian, N., & Borrelli, N. F. (1999). Room-temperature gain at 1.3 μm in PbS-doped glasses. Applied Physics Letters, 75(20), 3060-3062.
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  Abstract: We report on room-temperature optical gain at the ground exciton transition of PbS quantum-dot-doped glasses while optical pumping into the next-higher exciton resonance. The material gain in the quantum dots is as large as 80 cm-1. The dot-size selective excitation provides tunability of the optical gain. This is demonstrated by tuning the gain from 1317 to 1352 nm by changing the pump wavelength from 900 to 980 nm. © 1999 American Institute of Physics.
• Äyräs, P., Rantala, J. T., Honkanen, S., Mendes, S. B., & Peyghambarian, N. (1999). Diffraction gratings in sol-gel films by direct contact printing using a UV-mercury lamp. Optics Communications, 162(4), 215-218.
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  Abstract: We report on the fabrication of diffraction gratings in photosensitive sol-gel thin films by direct contact printing using a UV-mercury lamp. Titanium amplitude masks were used to replicate diffraction gratings into photosensitive sol-gel films by contact printing with an incoherent UV-light source. Gratings with 1-μm period were fabricated in sol-gel films. The diffraction efficiencies of each diffracted order were measured and compared to theoretical values. The demonstrated process of contact printing using a regular UV-light source in the optically compatible sol-gel material has potential for large-scale fabrication of submicrometer gratings at very low cost.
• Äyräs, P., Rantala, J. T., Levy, R., Descour, M. R., Honkanen, S., & Peyghambarian, N. (1999). Multilevel structures in sol-gel thin films with a single UV-exposure using a gray-scale mask. Thin Solid Films, 352(1-2), 9-12.
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  Abstract: Multilevel structures in sol-gel thin films with a single step process are demonstrated. A negative-tone hybrid sol-gel material is UV-exposed through a gray-scale calibration mask. Test strips of different depths and a continuous test profile are demonstrated. A maximum depth difference exceeding 1.5 μm is obtained, which permits the fabrication of multilevel diffractive elements for use in visible light. This method of using sol-gel material with a gray-scale mask has the potential for low-cost fabrication of complex multilevel micro-optical structures. © 1999 Elsevier Science S.A. All rights reserved.
• Bellmann, E., Shaheen, S. E., Marder, S. R., Kippelen, B., Grubbs, R. H., & Peyghambarian, N. (1998). Synthesis of high-T_g hole-transporting polymers with different redox potentials and their performance in organic two-layer LEDs. Proceedings of SPIE - The International Society for Optical Engineering, 3476, 322-331.
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  Abstract: Organic hole transport materials are used in organic LEDs, where they substantially improve device performance if placed as a hole transport layer (HTL) between the anode and the electroluminescent layer (EL). Soluble polymeric hole transport materials with high glass transition temperatures are of particular interest, because they allow for efficient device fabrication through spin casting of the HTL, and high glass transition temperatures have been found to improve thermal and long-term stability of the device. The redox potential of the hole transport material determines the facility of charge injection at the anode/HTL and the HTL/EL interfaces, thus affecting the overall device efficiency. We have synthesized a series of soluble hole-transporting polymers with glass transition temperatures in the range of 130 °C to 150 °C. The synthetic method allows facile substitution of the hole transport functionality with electron-withdrawing and electron-donating groups, which permits tuning of the redox potential of the polymer. These polymers have been used as HTL in two-layer devices ITO/HTL/Alq/Mg. The maximum external quantum efficiency increases, if the redox potential is changed to facilitate reduction of the hole transport material at the HTL/EL interface. Electron-deficient derivatives show higher external quantum efficiencies. The device stability, however, follows the opposite trend.
• Bellmann, E., Shaheen, S. E., Thayumanavan, S., Barlow, S., Grubbs, R. H., Marder, S. R., Kippelen, B., & Peyghambarian, N. (1998). New Triarylamine-Containing Polymers as Hole Transport Materials in Organic Light-Emitting Diodes: Effect of Polymer Structure and Cross-Linking on Device Characteristics. Chemistry of Materials, 10(6), 1668-1676.
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  Abstract: A series of poly(norbornenes) with pendant triarylamine (TPA) groups has been synthesized by ring-opening metathesis polymerization and investigated as hole transport materials in organic two-layer light-emitting diodes (LEDs). Efficient device fabrication through spin casting of the hole transport layer (HTL) was possible, since the polymers exhibited excellent film formation properties. LEDs of the form ITO/poly(norbornene)-TPA/Alq3/Mg (ITO = indium tin oxide, Alq3 = tris(8-quinolinato)aluminum) showed bright green emission with external quantum efficiencies of up to 0.77% (1.30 lm/W) for 20 nm thick HTL films. The length and polarity of the linker between the triarylamine functionality and the polymer backbone were varied systematically. The device performance was found to depend strongly on these structural differences. Substitution of ester groups by less polar ether functionalities greatly enhances external quantum efficiencies, lowers the operating voltage, and improves the stability of the device. Further improvement of the device characteristics is achieved by reducing the length of the alkyl linker. The HTL can be conveniently cross-linked by UV irradiation. Cross-linking was found to decrease device performance. A maximum external quantum efficiency of 0.37% was achieved for an Alq3-LED with cross-linked HTL.
• Giessen, H., Linden, S., Kuhl, J., Knorr, A., Koch, S. W., Gindele, F., Hetterich, M., Grun, M., Petillon, S., Klingshirn, C., & Peyghambarian, N. (1998). Coherent high-intensity pulse propagation on a free exciton resonance in a semiconductor. Physica Status Solidi (B) Basic Research, 206(1), 27-36.
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  Abstract: We present an experimental and theoretical study of high-intensity femtosecond pulse propagation on the free exciton resonance in CdSe. The results include pulse reshaping, pulse break-up, high transmission rates and a dip in the velocity dispersion for pulses tuned to the vicinity of the A-exciton. This corroborates evidence for nonlinear coherent on-resonance long-distance propagation in semiconductors.
• Golemme, A., Kippelen, B., & Peyghambarian, N. (1998). Highly efficient photorefractive polymer-dispersed liquid crystals. Applied Physics Letters, 73(17), 2408-2410.
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  Abstract: We report on high-resolution photorefractive polymer-dispersed liquid crystals that lead to high diffraction efficiency at lower applied fields compared with photorefractive polymers. The diffraction efficiency reaches 100% internally for 105-μm-thick samples at a field of 8 V/μm. Net optical gain and diffraction efficiencies of 56% are demonstrated in 53-μm-thick devices. Subsecond response times have also been obtained using polymeric matrices with good transport properties. © 1998 American Institute of Physics.
• Grace, K. M., Shrouf, K., Honkanen, S., Äyräs, P., Katila, P., Leppihalme, M., Johnston, R. G., Yang, X., Swanson, B. I., & Peyghambarian, N. (1998). Real time chemical detection using species selective thin films and waveguide zeeman interferometry. Proceedings of SPIE - The International Society for Optical Engineering, 3383, 27-32.
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  Abstract: We present a chemical sensor scheme based on selective sensing surfaces and highly sensitive integrated optical transduction methods. Using self-assembly techniques, species selective thin-films are covalently attached to the surface of Si3N4 channel waveguides to produce robust sensor elements. Exposure to targeted analyses results in the selective absorption of these molecules onto the waveguide surface causing a change in the effective refractive index of the guided modes. These relative changes in effective refractive index between TE and TM modes are precisely measured using Zeeman interferometry. Our measurements demonstrate reversible, real time sensing of volatile organic compounds at ppm levels.
• Hendrickx, E., Herlocker, J., Maldonado, J. L., Guillemet, G., Röckel, H., Erskine, L., Marder, S. R., Kippelen, B., & Peyghambarian, N. (1998). High-gain photorefractive polymers. Proceedings of SPIE - The International Society for Optical Engineering, 3281, 268-276.
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  Abstract: We report on the photorefractive properties of polymer composites based on the dye 2, N, Ndihexylamino-7-dicyanomethylidenyl-3, 4, 5, 6, 10-pentahydronaphthalene (DHADC-MPN). At 633 nm and with 2,4,7-trinitrofluorenone as a sensitizer, the polyvinylcarbazole-based composites show complete internal diffraction at applied electric fields as low as Eπ/2 = 30 V/μm. The sensitivity of the composite could be extended into the infrared by using (2,4,7-trinitro-9-fluorenylidene)malonitrile as a sensitizer, and at 830 nm complete internal diffraction occurred at an applied field of Eπ/2 = 59 V/μm. Finally, by using DHADC-MPN as a trifunctional dopant in an inert matrix, we have achieved a dynamic range of Δn = 0.0085 and a net two-beam coupling gain of Γ = 202 cm-1 at an applied field of 50 V/μm and at 633 nm. The composites are thermally stable or have shelf lifetimes of at least several years at room temperature.
• Hendrickx, E., Herlocker, J., Maldonado, J. L., Marder, S. R., Kippelen, B., Persoons, A., & Peyghambarian, N. (1998). Thermally stable high-gain photorefractive polymer composites based on a tri-functional chromophore. Applied Physics Letters, 72(14), 1679-1681.
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  Abstract: We report on the photorefractive properties of thermally stable polymer composites based on the dye 2, N, N-dihexylamino-7-dicyanomethylidenyl-3,4,5,6,10-pentahydronaphthalene. At an applied field of 50 V/μm, we have achieved a dynamic range of Δn=8.5×10-3 and a net two-beam coupling gain of 202cm-1. The diffraction efficiency peaks at an applied field of 28 V/μm, giving an external diffraction efficiency of 71%. © 1998 American Institute of Physics.
• Higuchi, H., Takahashi, M., Kawamoto, Y., Kadono, K., Ohtsuki, T., Peyghambarian, N., & Kitamura, N. (1998). Optical transitions and frequency upconversion emission of Er³⁺ ions in Ga₂S₃-GeS₂-La₂S₃ glasses. Journal of Applied Physics, 83(1), 19-27.
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  Abstract: Spectroscopic properties of Er3+ in Ga2S3-GeS2-La2S3 glasses are investigated on the basis of the spontaneous emission probabilities calculated by the use of the Judd-Ofelt theory and lifetime data. Frequency upconversion spectra are also measured with excitation at 800 and 980 nm. The spontaneous emission probabilities are much larger than those of the other glass systems such as oxides and fluorides. This is mainly attributed to the large refractive indices of the sulfide glasses. The quantum efficiencies of 4I11/2 and 4F9/2 levels are comparable or larger than the typical values of Er3+ in a fluoride glass. This is a consequence of the large spontaneous emission probabilities and low phonon energies of the sulfide glasses. However, the quantum efficiency of the 4S3/2 level is less than one-half of the value in the fluoride glass. The nonradiative transition probability of the 4S3/2 level is much larger than the value which is evaluated from the multiphonon relaxation theory. This suggests the presence of the other nonradiative relaxation process in addition to the multiphonon relaxation. This process is considered to be the energy transfer from the excited Er3+ to the band-gap excitation of the matrix glass. In upconversion spectra, the 497 nm emission from the 4F7/2 level is observed in addition to the red (665 nm) and the green (533 and 552 nm) emission bands. © 1998 American Institute of Physics.
• Jiang, S., Honkanen, S., Luo, T., Hwang, B., Nunzi-Conti, G., Myers, M., Rhonehouse, D., & Peyghambarian, N. (1998). Development and characterization of a new Er³⁺ doped phosphate glass for planar waveguide lasers and amplifiers. Proceedings of SPIE - The International Society for Optical Engineering, 3280, 40-45.
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  Abstract: A new Er3+ doped phosphate glass exhibiting an excellent durability in both boiling water and NaNO3 molten salt was developed. Ion-exchange process of this glass was investigated by treating glass samples in a variety of salt bathes with various exposure times. Planar waveguide with one mode at 1.54 μm and three modes at 632.8nm was demonstrated. Spectral properties of Er3+ in this glass were characterized by measuring absorption and emission spectra, and fluorescence lifetimes. Emission cross section of Er3+ in this glass was calculated to be 0.76×10-20 cm2 using McCumber theory. Our preliminary experimental results indicate this new Er3+ doped glass is an excellent material for ion-exchanged waveguide lasers and amplifiers.
• Jiang, S., Luo, T., Hwang, B., Nunzi-Conti, G., Myers, M., Rhonehouse, D., Honkanen, S., & Peyghambarian, N. (1998). New Er ³⁺-doped phosphate glass for ion-exchanged waveguide amplifiers. Optical Engineering, 37(12), 3282-3286.
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  Abstract: A new Er 3+doped phosphate glass exhibiting an excellent durability in both boiling water and NaNO 3 molten salt is developed. The ion-exchange process of this glass is investigated by treating glass samples in a variety of salt baths with various exposure times. A planar waveguide with one mode at 1.54 μm and three modes at 632.8 nm is demonstrated. The spectral properties of Er 3+ in this glass are characterized by measuring absorption and emission spectra and fluorescence lifetimes. The emission cross section of Er 3+ in this glass is calculated to be 0.76x 10 20 cm 2 using McCumber theory. ©1998 Society of Photo-Optical Instrumentation Engineers.
• Jiang, S., Luo, T., Myers, M., Myers, J., Lucas, J., & Peyghambarian, N. (1998). Phosphate glasses for high average power lasers. Proceedings of SPIE - The International Society for Optical Engineering, 3280, 2-13.
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  Abstract: Three phosphate glasses Nd3+ doped QX/Nd, Er3+ doped QX/Er and Yb3+ doped QX/Yb were developed for high average power lasers. It was shown that all three phosphate laser glasses exhibited high strength, low thermal expansion coefficient and optical athermal behavior. Enhancement of thermal loading capabilities of the glasses were achived by ion-exhcange chemical strengthening processes. Experiments indicated that problems regarding thermal loading and resulting stress induced birefriengence for QX/Yb were comparable for Yb:YAG crystals.
• Jiang, S., Myers, M., & Peyghambarian, N. (1998). Er³⁺ doped phosphate glasses and lasers. Journal of Non-Crystalline Solids, 239(1-3), 143-148.
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  Abstract: Phosphate glass samples with various Cr2C3, Yb2O3, and Er2O3 contents based upon 67P2O5·14Al2O 3·14Li2O·1K2O·4(Yb 2O3 + Er2O3) were prepared. The effect of changing concentrations of Er3+ ions (0.1-1.5 × 1019 ions cm-3) and sensitizers Cr3+ ion and Yb3+ ion (2-16 × 1018 ions cm-3 and 1.35-2.3 × 1021 ions cm-3 respectively) on laser performance were investigated. The thermal shock resistance of this glass was doubled after an ion-exchange chemical strengthening process in a KNO3/NaNO3 molten salt bath. Lasers with repetition rates of 20 Hz at free-running and 15 Hz at Q-switched single mode were demonstrated by utilizing chemically strengthened laser glass rods. © 1998 Elsevier Science B.V. All rights reserved.
• Kawabe, Y., Morrell, M. M., Jabbour, G. E., Shaheen, S. E., Kippelen, B., & Peyghambarian, N. (1998). A numerical study of operational characteristics of organic light-emitting diodes. Journal of Applied Physics, 84(9), 5306-5314.
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  Abstract: We propose a simple model for the device characteristics of organic single layer molecular or polymeric light-emitting diodes. The model is based on Poisson's equation and the conservation law of charges. A bimolecular recombination process is incorporated phenomenologically, and boundary conditions are given by carrier injection functions. Equations for the electric field and carrier concentrations are formulated for single-carrier and double-carrier injection cases. The equations are solved for different parameters including carrier mobility and energy barrier height at the electrodes. Current-voltage characteristics, relative quantum efficiency, and emission distribution are obtained. The results show that (1) at least one barrier height should be low for device operation at low voltage (2) high mobility is essential for devices with high brightness, (3) low electron mobility confines the emission region near the cathode and should be avoided to prevent electrode quenching. We also discuss the effects from persistent charged traps. The calculation was compared with experimental results obtained by single layer conjugated polymer and dye-doped polymer devices. Fairly good agreement between experiments and calculations on the current-voltage characteristics and relative quantum efficiency were obtained using reasonable physical parameters. © 1998 American Institute of Physics.
• Kippelen, B., Golemme, A., Madonado, J. L., & Peyghambarian, N. (1998). Efficient photorefractive polymer dispersed liquid crystals. Conference on Lasers and Electro-Optics Europe - Technical Digest, 33-.
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  Abstract: The photorefractive polymer dispersed liquid crystals (PDLCs) doped with the liquid crystal TL202 is studied. In samples with composition PMMA:TL202:ECZ:TNFDM, an external diffraction efficiency of 55% at 633 nm in 53-μm-thick samples at an applied field of 20 V/μm for a grating spacing of 3 μm is achieved. In 105-μm-thick samples of the same mixture, the diffraction efficiency exhibits a first maximum at an applied field of 8 V/μm and for a grating spacing of 3 μm. At an applied field of 8 V/μm, these new materials have a dynamic range that is >50 times higher than in DMNPAA:PVK:ECZ:TNF polymers.
• Kippelen, B., Golemme, A., Maldonado, J. L., & Peyghambarian, N. (1998). Photorefractive polymer dispersed liquid crystals. Proceedings of SPIE - The International Society for Optical Engineering, 3297, 28-36.
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  Abstract: Organic photorefractive materials have received increasing attention for photonic applications due to their high performance level and their ease of processing. Here, we present functionalized polymer dispersed liquid crystals that exhibit strong photorefractive properties. Their properties are investigated by wave-mixing experiments and their performance compared with photorefractivc polymers and photorefractive liquid crystals.
• Kippelen, B., Hendrickx, E., Herlocker, J., Maldonado, J. L., Marder, S. R., & Peyghambarian, N. (1998). Thermally stable high-gain photorefractive polymers based on a trifunctional chromophore. Conference on Lasers and Electro-Optics Europe - Technical Digest, 30-.
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  Abstract: A stable polymer composite that was prepared by mixing the dye DHADC-MPN with an inert polymer-plasticer matrix has been developed. An unprecendented polymer composite with two-beam coupling gain coefficient of 225 cm-1 at 50 V/μm, and an external diffraction efficiency of 71% was achieved at an external field of 28 V/μm for 633-nm operation. The addition of 0.18 wt.% of TNFDM greatly reduces the buildup time and slightly improves the photorefractive response.
• Kippelen, B., Herlocker, J., Maldonado, J. L., Ferrio, K., Hendrickx, E., Mery, S., Golemme, A., Marder, S. R., & Peyghambarian, N. (1998). Progress in organic photorefractive material development. Proceedings of SPIE - The International Society for Optical Engineering, 3471, 22-28.
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  Abstract: The refractive index modulation in photorefractive polymers with a low glass transition temperature is dominated by orientation birefringence effects. To take advantage of these effects we developed several photorefractive polymers that contain: (i) chromophores designed to have simultaneously a large dipole moment and a high linear polarizability anisotropy, (ii) nematic phase liquid crystal droplets, (iii) transparent molecules generally used for liquid crystal applications. We discuss recent advances in these three different classes of materials and emphasize their merits and trade-off.
• Kippelen, B., Marder, S. R., Hendrickx, E., Maldonado, J. L., Guillemet, G., Volodin, B. L., Steele, D. D., Enami, Y., Sandalphon, ., Yao, Y. J., Wang, J. F., Röckel, H., Erskine, L., & Peyghambarian, N. (1998). Infrared photorefractive polymers and their applications for imaging. Science, 279(5347), 54-57.
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  PMID: 9417020;Abstract: Photorefractive polymers with high diffraction efficiency in the visible and near-infrared regions of the electromagnetic spectrum have been developed. These polymers, which have a large dynamic range because of their high orientational birefringence, incorporate a dye designed to have a large dipole moment and a high linear polarizability anisotropy. Such polymers have enabled demonstrations of imaging through scattering media, using a holographic time-gating technique at a wavelength that is comparable with the transparency of biological tissues and with the emission of low-cost semiconductor laser diodes.
• Kippelen, B., Peyghambarian, N., & Marder, S. R. (1998). Photorefractive polymers for biomedical imaging. Optics and Photonics News, 9(12), 16-17.
• Laine, J. -., Honkanen, S., Tervonen, A., & Peyghambarian, N. (1998). Modeling of planar ion-exchanged Er ³⁺-doped glass waveguide amplifiers. Optical Engineering, 37(4), 1182-1187.
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  Abstract: Modeling results for Er 3+-doped waveguide amplifiers fabricated by various ion-exchange processes are presented. The gain performance of these devices for 0.98- and 1.48-μm pump wavelengths are compared. Measured spectroscopic properties of a phosphate glass with Er 3+ concentration of 3.7×10 20 cm -3 are used throughout the modeling, and waveguide propagation loss of 0.1 to 0.6 dB/cm is used. It is shown that gain coefficients exceeding 5 dB/cm are feasible utilizing optimized ion-exchanged waveguides in this glass. The modeling is performed for glasses doped with erbium only, excluding possible ytterbium codoping. © 1998 Society of Photo-Optical Instrumentation Engineers.
• Luo, T., Jiang, S., Conti, G. N., Honkanen, S., Mendes, S. B., & Peyghambarian, N. (1998). Ag⁺-Na⁺ exchanged channel waveguides in germanate glass. Electronics Letters, 34(23), 2239-2240.
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  Abstract: Singlemode and multimode Ag+-Na+ exchanged channel waveguides have been formed in germanate glass. The mode profiles and propagation losses of these channel waveguides at 1.55μm have been measured. The measured propagation loss is < 2dB/cm in channel waveguides.
• Mathine, D. L., Jabbour, G. E., Morrell, M. M., Shaheen, S. E., Kawabe, Y., Kippelen, B., & Peyghambarian, N. (1998). Fabrication of micropixel arrays of bright organic electroluminescent devices. Conference on Lasers and Electro-Optics Europe - Technical Digest, 7-.
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  Abstract: A simple method for the microfabrication vacuum-deposited organic light-emitting diodes has been developed to form micropixel arrays of light-emitting devices. These arrays have applications in high-definition displays. The properties of the resulting device are presented.
• Nordman, O., Nordman, N., & Peyghambarian, N. (1998). Electron beam induced changes in the refractive index and film thickness of amorphous As_xS_100-x and As_xSe_100-x films. Journal of Applied Physics, 84(11), 6055-6058.
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  Abstract: In this article, electron beam induced changes in the refractive index and film thickness of time relaxed amorphous AsxS100-x (with x = 30-45) and AsxSe100-x (with x = 40-70) are studied. The largest index change (∼0.08) in AsxS100-x films is found when x = 40. The corresponding value (∼0.06) for AsxSe100-x films is met when x = 55. The difference in the best compositions is attributed to the different relaxation processes of As-S and As-Se films. Electron beam irradiation causes surface shrinkage of the films. In AsxSe100-x films contactions are deepest (∼75 nm) when x = 55. © 1998 American Institute of Physics.
• Peyghambarian, N., Kippelen, B., Marder, S. R., Hendrickx, E., Maldonado, J. L., Guillemet, G., Volodin, B. L., Steele, D. D., Enami, Y., Sandalphon, ., Yao, Y. J., Wang, J. F., Röckel, H., Erskine, L., & Peyghambarian, N. N. (1998). Infrared photorefractive polymers and their applications for imaging. Science (New York, N.Y.), 279(5347).
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  Photorefractive polymers with high diffraction efficiency in the visible and near-infrared regions of the electromagnetic spectrum have been developed. These polymers, which have a large dynamic range because of their high orientational birefringence, incorporate a dye designed to have a large dipole moment and a high linear polarizability anisotropy. Such polymers have enabled demonstrations of imaging through scattering media, using a holographic time-gating technique at a wavelength that is compatible with the transparency of biological tissues and with the emission of low-cost semiconductor laser diodes.
• Rantala, J. T., Nordman, N., Nordman, O., Vähäkangas, J., Honkanen, S., & Peyghambarian, N. (1998). Sol-gel hybrid glass diffractive elements by direct electron-beam exposure. Electronics Letters, 34(5), 455-456.
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  Abstract: The authors propose and demonstrate direct electron-beam writing of surface relief diffractive elements into hybrid inorganic/ organic sol-gel glass films. The etch depth and phase delay can be controlled by the electron dose. The potential applications include multi-phase-level diffractive elements and apodised planar waveguide gratings.
• Rantala, J. T., Äyräs, P., Levy, R., Honkanen, S., Descour, M. R., & Peyghambarian, N. (1998). Binary-phase zone-plate arrays based on hybrid solgel glass. Optics Letters, 23(24), 1939-1941.
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  PMID: 18091962;Abstract: An organically modified silane zirconate-based solgel material is used for the fabrication of binary-phase zone-plate arrays. The synthesized hybrid solgel material has a negative tone under UV exposure and can be patterned by a UV-lithography process. The transmittance of the material is nearly 100%, and the refractive index is 1.52. Two different diffractive lens arrays with focal lengths of 5 and 42 cm have been fabricated. The average roughness of the zone surface is less than 20 nm. The diffraction efficiencies of the lens arrays are measured as a function of modulation depth and exposure dose. A diffraction efficiency of 30% is achieved. © 1998 Optical Society of America.
• Rantala, J., Jabbour, G. E., Vähäkangas, J., Honkanen, S., Kippelen, B., & Peyghambarian, N. (1998). Hybrid sol-gel micro-patterning of organic electroluminescent devices. Japanese Journal of Applied Physics, Part 2: Letters, 37(10 PART A), L1098-L1100.
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  Abstract: We demonstrate a novel technique of fabricating organic light-emitting devices. Each device consists of 1480 micro-pixels, with a pixel dimension of 45×45μm2. The pixels were obtained by using a single-step UV patternable sol-gel hybrid glass thin film. Due to higher fields, micro-pixels based devices show forward light output at lower voltage than conventional dvices. More than 1% in external quantum efficiency and green light exceeding 27,000 cd/m2 are demonstrated.
• Schülzgen, A., & Peyghambarian, N. (1998). Excitation front propagation in a semiconductor induced by high-intensity femtosecond laser pulses. Proceedings of SPIE - The International Society for Optical Engineering, 3283, 740-747.
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  Abstract: We report on the excitation and propagation of an exciton density front inside a semiconductor that is characterized by high absorption and large optical nonlinearity. Femtosecond optical pulses are used for both the excitation of the density front and the probe of the front propagation. We analyze in detail the spectra of reflected probe pulses that carry information about the propagating density front due to partial internal reflection of light at the boundary between regions of high and low excitation density. Time resolved data show that the Doppler shift of the internal reflection is limited to the duration of the pump pulse indicating the highly transient character of the exciton front propagation. ©2003 Copyright SPIE - The International Society for Optical Engineering.
• Schülzgen, A., Peyghambarian, N., & Hughes, S. (1998). Doppler-shifted self-reflection from a semiconductor. Physica Status Solidi (B) Basic Research, 206(1), 125-130.
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  Abstract: We report the experimental observation of a self-reflected wave inside a dense saturable absorber. A femtosecond pulse saturates the absorption and causes a density front to penetrate into the semiconductor. The dielectric constant change across the boundary between areas of low and high densities results in internal reflection. Due to the front propagation the self-reflected light is shifted by the Doppler effect. The Doppler shift makes it possible to distinguish between surface reflection and self-reflection and is used to experimentally verify the dynamic nonlinear skin effect. The measurements are in agreement with our theory which is within the framework of the reduced semiconductor Maxwell-Bloch equations.
• Scifres, D., Weiner, A., Corkum, P., & Peyghambarian, N. (1998). Lasers in Earth and planetary exploration. Technical Digest - European Quantum Electronics Conference, 24-25.
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  Abstract: Laser have been a tool of the space programs of the world for accomplishing a variety of engineering and scientific objectives. Mars Orbiter Laser Altimeter (MOLA) and NEAR spacecraft, which carries a laser ranger (NLR) represent a new class of active remote sensing instruments for conducting science in the solar system. These instruments determine the formation, dynamics and evolution of the planets, and even the solar system itself.
• Spiegelberg, C., Schulzgen, A., Kawabe, Y., Honkanen, S., Kippelen, B., Allemand, P. M., Kuwata-Gonokami, M., Takeda, K., & Peyghambarian, N. (1998). Whispering-gallery modes in microring lasers made from conjugated polymers. Conference on Lasers and Electro-Optics Europe - Technical Digest, 486-487.
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  Abstract: A study was conducted to demonstrate threshold behavior of laser modes in two different microring configurations under optical excitation. The first microring studied was formed by coating the conjugated polymer BEH-PPV on an etched fiber with a typical diameter of 50-100 μm and a polymer film thickness of 0.3 nm.
• Spiegelberg, C., Schülzgen, A., Allemand, P. M., Kippelen, B., & Peyghambarian, N. (1998). Gain dynamics in conjugated polymers at room temperature. Physica Status Solidi (B) Basic Research, 206(1), 131-138.
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  Abstract: We report on stimulated emission and optical gain in BEH-PPV polymer films at room temperature. Performing femtosecond pump-probe experiments we find very fast (≤100 fs) relaxation of excitons within a ladder of vibronic states. From spectra taken at very early times after photoexcitation we identify several vibronic transitions with a linewidth of about 8 nm. Strong coupling of excitons to these vibrations leads to stimulated emission and large optical gain of up to 104 cm-1. For a pump-probe delay of 200 fs the different tiansitions are no longer distinguishable due to broadening through spectral diffusion and exciton migration. The lifetime of the optical gain corresponds to the exciton lifetime. Population depletion by stimulated emission leads to a density dependent decay within a few hundred fs up to about 2 ps.
• Steele, D. D., Volodin, B. L., Savina, O., Kippelen, B., Peyghambarian, N., Röckel, H., & Marder, S. R. (1998). Transillumination imaging through scattering media by use of photorefractive polymers. Optics Letters, 23(3), 153-155.
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  PMID: 18084443;Abstract: We demonstrate the use of a near-infrared-sensitive photorefractive polymer with high efficiency for imaging through scattering media, using an all-optical holographic time gate. Imaging through nine scattering mean free paths is performed at 800 nm with a mode-locked continuous-wave Ti:sapphire laser. © 1998 Optical Society of America.
• Stenger-Smith, J., Zarras, P., Merwin, L. H., Shaheen, S. E., Kippelen, B., & Peyghambarian, N. (1998). Synthesis and characterization of poly(2,5-bis(n-methyl-n-hexylamino)phenylene vinylene), a conjugated polymer for light-emitting diodes. Macromolecules, 31(21), 7566-7569.
• Talanina, I., Burak, D., Binder, R., Giessen, H., & Peyghambarian, N. (1998). Theoretical study of solitonlike propagation of picosecond light pulses interacting with Wannier excitons. Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, 58(1), 1074-1080.
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  Abstract: An analytical and numerical study of light pulse propagation in semiconductors, with pulses spectrally centered at the lowest exciton resonance, is presented. It is shown that, in the limit of negligible phase-space blocking effects, the equation for the excitonic polarization is equivalent to a modified version of the nonlinear Schrödinger equation, for which soliton solutions have been derived by Mihalache et al. [D. Mihalache et al., Phys. Rev. A 47, 3190 (1993)]. The numerical study demonstrates the solitonlike propagation of experimentally relevant input pulses in CdSe crystal and assesses the influence of phase-space blocking effects and dephasing processes.
• Äyräs, P., Conti, G. N., Honkanen, S., & Peyghambarian, N. (1998). Birefringence control for ion-exchanged channel glass waveguides. Applied Optics, 37(36), 8400-8405.
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  PMID: 18301666;Abstract: We show that at 1.55-μm wavelength the waveguide birefringence of ion-exchanged channel waveguides in glass can be broadly tuned by a potassium and silver double-ion exchange. Two different potassium and silver double-ion-exchange processes are used to make surface waveguides with negligible waveguide birefringence. This process is crucially important in the manufacture of devices for dense wavelength-division multiplexing systems. The dependence of the waveguide birefringence on the channel width is also reported. © 1998 Optical Society of America.
• Äyräs, P., Honkanen, S., Grace, K. M., Shrouf, K., Katila, P., Leppihalme, M., Tervonen, A., Yang, X., Swanson, B., & Peyghambarian, N. (1998). Thin-film chemical sensors with waveguide Zeeman interferometry. Pure and Applied Optics (Print edition) (United Kingdom), 7(6), 1261-1271.
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  Abstract: We describe a highly sensitive chemical sensor scheme using a Si3N4 channel waveguide with a selective surface coating based on polarimetric Zeeman interferometry. The sensing is based on measurement of the phase difference between TE and TM modes propagating in the anisotropic waveguide structure under exposure to toluene vapour. A real-time and reversible response at low ppm level is observed. Modelling results of the sensor structure to further increase its sensitivity are presented. © 1998 IOP Publishing Ltd.
• Golemme, A., Volodin, B. L., Kippelen, B., & Peyghambarian, N. (1997). Photorefractive polymer-dispersed liquid crystals. Optics Letters, 22(16), 1226-1228.
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  PMID: 18185802;Abstract: We report observation of the photorefractive effect in functionalized polymer-dispersed liquid crystals. The photoconductive properties are provided by the polymer matrix, and the field-dependent refractive-index changes are generated by the dispersed nematic liquid-crystal droplets. A high diffraction efficiency (8%) and a high refractive-index modulation amplitude (Δn = 2 × 10-3) are obtained in 53-μm-thick samples with an applied field of 22 V/μm. © 1997 Optical Society of America.
• Grace, K. M., Shrouf, K., Honkanen, S., Äyräs, P., Katila, P., Leppihalme, M., Johnston, R. G., Yang, X., Swanson, B., & Peyghambarian, N. (1997). Waveguide Zeeman interferometry for thin-film chemical sensors. Electronics Letters, 33(19), 1651-1653.
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  Abstract: The authors demonstrate a highly sensitive chemical sensor scheme based on Si3N4 channel waveguides, species-selective surface coatings and Zeeman interferometry. The relative phase change between the TE and TM modes under exposure to toluene vapour is measured. The measurements demonstrate the real-time and reversible response with good sensitivity at low concentrations.
• Guerreiro, P. T., Ten, S., Borrelli, N. F., Butty, J., Jabbour, G. E., & Peyghambarian, N. (1997). PbS quantum-dot doped glasses as saturable absorbers for mode locking of a Cr:forsterite laser. Applied Physics Letters, 71(12), 1595-1597.
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  Abstract: Quantum confined nanocrystals of PbS in glass were used as intracavity saturable absorbers to obtain passive continuous-wave mode locking in a Cr:forsterite laser. We obtained near transformed-limited 4.6 ps laser pulses at 110 MHz repetition rate, and a wide tunability range of 1207-1307 nm. The absorption saturation intensity of the quantum-dot PbS doped glasses was measured to be 0.2 MW/cm2. © 1997 American Institute of Physics.
• Guerreiro, P. T., Ten, S., Slobodchikov, E., Kim, Y. M., Woo, J. C., & Peyghambarian, N. (1997). Self-starting mode-locked Cr:Forsterite laser with semiconductor saturable Bragg reflector. Optics Communications, 136(1-2), 27-30.
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  Abstract: We report the self-starting passively mode-locked operation of a chromium-doped forsterite laser using a semiconductor saturable Bragg reflector. Self-starting mode-locking was the only operational mode of the laser and could be achieved with and without intracavity dispersion compensation. We obtained 110 fs transformed limited pulses using a prism pair for dispersion compensation, 4 ps pulses without prisms, and pulse energies of up to 2.3 nJ at 90 MHz repetition rate.
• Guerreiro, P. T., Ten, S., Slobodchikov, E., Kim, Y. M., Woo, J. C., & Peyghambarian, N. (1997). Self-starting modelocked Cr:forsterite laser with semiconductor saturable Bragg reflector. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 11, 123-.
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  Abstract: Self-starting modelocked operation of a chromium-doped forsterite laser using saturable Bragg reflectors (SBRs) is demonstrated. A typical intensity autocorrelation and spectrum of the laser output transmitted through the SBR were seen. A train of chirped pulses with average output power of 210 mW corresponding to pulse energies of 2.3 nJ were obtained by replacing the flat high reflector by a 4.5% output coupler. Chirped picosecond pulses were also obtained when laser is operated without the prism pair.
• Hendrickx, E., Volodin, B. L., Steele, D. D., Maldonado, J. L., Wang, J. F., Kippelen, B., & Peyghambarian, N. (1997). Phase stability of guest/host photorefractive polymers studied by light scattering experiments. Applied Physics Letters, 71(9), 1159-1161.
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  Abstract: We report on light scattering measurements in guest/host photorefractive polymers doped with different polar dyes as a function of temperature and sample composition. Crystallization processes of the polar dye are found to follow a nucleation and growth mechanism. The structure and melting point of the polar dye, the storage temperature, and the amount of plasticizer are shown to exert a major influence on the shelf lifetime of the samples. New composites with high efficiency and long shelf lifetime are presented. © 1997 American Institute of Physics.
• Honkanen, S., Laine, J., Ohtsuki, T., Tervonen, A., & Peyghambarian, N. (1997). Modeling of Er-doped ion-exchanged glass waveguide amplifiers. Proceedings of SPIE - The International Society for Optical Engineering, 2996, 103-108.
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  Abstract: Modeling results for Er3+-doped waveguide amplifiers fabricated by various ion-exchange processes are presented. The gain performance of these devices for 977 nm and 1.48 micrometers pump wavelengths are compared. Measured spectroscopic properties of a phosphate glass with Er3+ concentration of 3.7 X 1020 cm-3 are used throughout the modeling, and waveguide propagation loss of 0.1 dB/cm is used. It is shown that gain coefficients exceeding 5 dB/cm are feasible utilizing optimized ion- exchanged waveguides in this glass. The modeling is performed for glasses doped with erbium only, excluding possible ytterbium codoping. ©2004 Copyright SPIE - The International Society for Optical Engineering.
• Honkanen, S., Ohtsuki, T., Jiang, S., Najafi, S. I., & Peyghambarian, N. (1997). High Er concentration phosphate glasses for planar waveguide amplifiers. Proceedings of SPIE - The International Society for Optical Engineering, 2996, 32-40.
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  Abstract: Cooperative upconversion processes and Yb-Er energy transfer efficiencies in high Er concentration phosphate glasses were studied. The cooperative upconversion coefficients were deduced from the pump intensity dependence of luminescence decay curves. Cooperative upconversion coefficients of 4I13/2 level, for Er3+ concentrations higher than 1 X 1020 cm-3, are one order of magnitude smaller than the ones reported for silica glass. The increase in the cooperative upconversion coefficient with the increase in Er3+ concentration was found to be small and Er3+ concentrations as high as 3.7 X 10 20 cm3+ in this glass are feasible. Yb-Er energy transfer efficiency in Yb/Er co-doped phosphate glasses, with Er concentrations as high as 1.9 X 1020 cm-3 and 2.4 X 1020 cm -3, were measured with a pump and probe technique and also estimated from lifetime measurements. The energy transfer efficiencies exceed 95 percent, although the ratio of the concentrations, Yb/Er, is only about 1.2 and 2 in the samples studied.This confirms that efficient pumping of high Er3+ concentration phosphate glass, required in waveguide amplifiers, can be achieved utilizing Yb/Er co-doping. ©2004 Copyright SPIE - The International Society for Optical Engineering.
• Jabbour, G. E., Kawabe, Y., Shaheen, S. E., Wang, J. F., Morrell, M. M., Kippelen, B., & Peyghambarian, N. (1997). Highly efficient and bright organic electroluminescent devices with an aluminum cathode. Applied Physics Letters, 71(13), 1762-1764.
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  Abstract: The electron injection process, which limits the electroluminescent performance of organic devices, has been enhanced tremendously by inserting a layer of LiF with appropriate thickness between the cathode and a quinacridone doped organic layer. Devices with an Al/LiF cathode demonstrated a luminance in excess of 20 000 cd/m2 and an external quantum efficiency of 3%, which is comparable to devices with a Mg/LiF cathode. These devices show maximum luminance of 45 000 cd/m2 prior to failure in continuous bias operation. For the same LiF thickness, the operating voltage for devices with Al/LiF was lower than the corresponding operating voltage for devices with Mg/LiF or Mg alone. Tunneling theory is used to explain this enhancement. © 1997 American Institute of Physics.
• Jabbour, G. E., Mathine, D. L., Kippelen, B., & Peyghambarian, N. (1997). Micro-pixel arrays of bright organic electroluminescent devices for high definition displays. Electronics Letters, 33(24), 2070-2071.
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  Abstract: Arrays of 600 micro-pixels of organic light emitting devices were fabricated by vacuum deposition of organic molecules. Pixels with dimensions as small as 20 X 20μm2 were easily achieved. Individual pixels showed bright green light in excess of 28,500cd/ m2 in CW mode.
• Jabbour, G. E., Shaheen, S. E., Kawabe, Y., Morrell, M. M., Cho, S. J., Wang, J. F., Kippelen, B., & Peyghambarian, N. (1997). Novel techniques in fabricating more efficient and brighter organic electroluminescent devices. Proceedings of SPIE - The International Society for Optical Engineering, 3148, 2-13.
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  Abstract: In this paper, we present two techniques for fabricating efficient and bright organic light emitting devices. The first technique allows for an enhancement in the electron injection process. This is accomplished through inserting a layer of LiF with appropriate thickness between the cathode and a quinacridone doped organic layer. Devices with an Al/LiF cathode demonstrated a luminance in excess of 20,000 cd/m2 and an external quantum efficiency of 3%, which is comparable to devices with a Mg/LiF cathode. These devices show maximum luminance of 45,000 cd/m2 prior to failure in continuous bias operation. In the second technique, partially ionized beam deposition was utilized in the fabrication process of organic electroluminescent devices. Preliminary results indicate that devices fabricated with this technique are more efficient and brighter than similar devices fabricated with the traditional thermal evaporation process.
• Kadono, K., Takahashi, M., Higuchi, H., Shojiya, M., Ohtsuki, T., Kawamoto, Y., & Peyghambarian, N. (1997). Frequency upconversion of Er³⁺ in Ga₂S ₃-GeS₂-La₂S₃ glasses. Proceedings of SPIE - The International Society for Optical Engineering, 2996, 25-31.
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  Abstract: Glasses containing Er3+ ions of 0.3 to 7 cation mol percent were prepared in the system of Ga2S3-GeS2-LaS 3. Frequency upconversion spectra of Er3+ in the glasses were measured under the excitation at 800 nm and 980 nm. Green emissions at 533 nm (2H11/2yields4I15/2) and 552 nm (4S3/2yields4I15/2), and red emission at 665 nm (4F9/2yields4I 15/2) were observed.In addition to these emission bands, 497 nm emission assigned to the 4F7/2yields4I 15/2 transition was observed. The spectral properties are analyzed from the view points of low phonon energy property and high refractive index. ©2004 Copyright SPIE - The International Society for Optical Engineering.
• Kanner, G. S., Strouse, G. F., Swanson, B. I., Sinclair, M., Jiang, J. P., & Peyghambarian, N. (1997). Subpicosecond dynamics of excitons and photoexcited intrinsic polarons in the quasi-one-dimensional solid PtCl. Physical Review B - Condensed Matter and Materials Physics, 56(5), 2501-2509.
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  Abstract: Subpicosecond transient absorption (TA) spectroscopy was used to identify excited states, and to measure their relaxation kinetics as a function of excitation wavelength in the halogen-bridged transition-metal (MX) compound PtCl. For pump photon energies Epump between 1.3 and 1.8 eV, below the threshold for exciton formation, intrinsic polarons are photoexcited and decay within 1-3 ps. Excitation into the exciton absorption tail (2.0-2.3 eV) yields singlet excitons that rapidly decay into an even-parity state, which has a lifetime (∼100 ps) varying with the intial photon energy. Excitation (3.1 eV) well above the exciton threshold appears to generate more slowly decaying excitons, as well as polarons that are formed upon exciton dissociation. The TA spectra also indicate that relaxation of excitons for Epump >2 eV is mediated by large-amplitude vibrations perpendicular to the chains. Using third-harmonic generation spectroscopy in addition to TA, we develop an energy-level diagram for the excited states, including polaron levels, and the lowest odd- and even-parity excitons.
• Kawabe, Y., Jabbour, G. E., Shaheen, S. E., Kippelen, B., & Peyghambarian, N. (1997). A model for the current-voltage characteristics and the quantum efficiency of single-layer organic light emitting diodes. Applied Physics Letters, 71(10), 1290-1292.
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  Abstract: A model for the current-voltage characteristics and the quantum efficiency of single-layer organic light emitting diodes is presented. With variables such as the electric field, the hole, and electron carrier densities, a set of coupled nonlinear differential equations is derived by using classical electrostatics and by assuming Fowler-Nordheim injection. Numerical calculations for different carrier mobility and barrier height conditions show that low barrier height at both electrodes leads to higher efficiency and higher carrier mobility leads to higher brightness. We find that for applications that require high current injection such as lasers, materials with high mobility are desired to reduce space charge effects. © 1997 American Institute of Physics.
• Kippelen, B., Golemme, A., Volodin, B. L., & Peyghambarian, N. (1997). Photorefractivity in polymer dispersed liquid crystals. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 11, 334-.
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  Abstract: Polymer dispersed liquid crystals (PDLC) combine the high resolution of photorefractive polymers and the high refractive index changes associated with field-induced reorientation of nematic liquid crystals. The materials are prepared by dispersing liquid crystal droplets of almost spherical shape in a photoconducting solid organic polymer matrix. The sensitizing, photoconducting and trapping properties necessary for the buildup of space-charge field are provided by the polymer matrix and the refractive index changes are due to the field-induced reorientation of the liquid crystal droplets. Polymethylmethacrylate doped with ethylcarbazole was used in the experiment.
• Kippelen, B., Meyers, F., Peyghambarian, N., & Marder, S. R. (1997). Chromophore design for photorefractive applications. Journal of the American Chemical Society, 119(19), 4559-4560.
• Kippelen, B., Sandalphon, ., Volodin, B. L., Meerholz, K., & Peyghambarian, N. (1997). Organic Polymers for Photorefractive Applications. ACS Symposium Series, 672, 218-235.
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  Abstract: We review the physics of highly efficient low glass transition temperature photorefractive polymers. Different design approaches to photorefractivity in organic polymers are discussed. Frequency-dependent ellipsometry and dielectric experiments are presented in poly(N-vinylcarbazole)-based materials. Orientational enhancement effects that lead to high efficiencies are clearly identified. Observation of non-Bragg diffraction orders is reported and their properties including phase-conjugation and phase-doubling are demonstrated.
• Kippelen, B., Volodin, B. L., Savina, O., Sandalphon, ., Rockel, H., Erskine, L., Marder, S. R., & Peyghambarian, N. (1997). Photorefractive polymers with improved efficiency. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 11, 335-.
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  Abstract: A new photorefractive polymer composite based on a polyvinylcarbazole matrix and doped with the new chromophore HR-2-54 with a strong orientational efficiency was developed. The photorefractive properties of the new composites were studied by four-wave mixing and two-beam coupling experiments. The structure of the molecule was carefully designed to prevent photoisomerization and to ensure good solubility in the photoconducting matrix and to prevent crystallization. The nonlinear response of the chromophore was measured with the frequency-dependent ellipsometry technique. The results of the study for photorefractive polymer composites are presented.
• Kippelen, B., Volodin, B. L., Steele, D. D., Hendrickx, E., Sandalphon, N., Enami, Y., Maldonado, J., Wang, J. F., Golemme, A., Röckel, H., Marder, S. R., Javidi, B., & Peyghambarian, N. (1997). New advances in organic photorefractive material development. Proceedings of SPIE - The International Society for Optical Engineering, 3144, 176-184.
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  Abstract: The rapid improvement of the performance of photorefractive polymers over the past few years has generated a strong technological interest for these new materials. The areas of application include holographic storage, image processing, optical correlation, and phase conjugation. This paper reviews some of our recent advances in the field of organic photorefractive materials. We will first present several new polymeric composites that combine high efficiency and long shelf lifetimes. Then we will discuss the performance of a new class of organic photorefractive materials: photorefractive polymer dispersed liquid crystals. Finally, we will present two examples of applications based on photorefractive polymers: (i) optical correlators for security verification, and (ii) imaging through scattering media in the near infra-red. ©2005 Copyright SPIE - The International Society for Optical Engineering.
• Kippelen, B., Volodin, B. L., Steele, D., Sandalphon, ., Marder, S. R., & Peyghambarian, N. (1997). High-efficiency photorefractive polymers based on new design strategies. Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest, 74-75.
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  Abstract: A new chromopore, named HR-2-54, was designed as a doping agent for developing new photorefractive polymer composites. As observed by frequency-dependent ellipsometry, the chromopore has a strong polarizability anisotropy that can lead to high efficiency in low Ts polymers. Four wave mixing experiments on a HR-2-54:PVK:ECZ:TNF samples demonstrated a four-fold improvement in refractive index modulation compared with previous polymers, while asymmetric two-beam coupling experiments confirm the photorefractive nature of these highly efficient gratings. Samples with 40% chromopore loading showed excellent stability. Maximum diffraction could be observed at 830 nm in 105 μm-thick samples of HR-2-54:PVK:ECZ:TNFDM at an applied field of 50 V/μM.
• Li, C., Fuflyigin, V., Zhao, J., Chen, X., Honkanen, S., & Peyghambarian, N. (1997). Er-doped fluoride glass films by MOCVD for waveguide devices. Proceedings of SPIE - The International Society for Optical Engineering, 2996, 68-73.
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  Abstract: We report on the growth of erbium doped ZrF4-LaF3- BaF2 glass films by metalorganic chemical vapor deposition (MOCVD) for the construction of planar waveguide devices. Our process provides the growth of high quality, uniform in thickness, and continuous films on a wide variety of common substrates. A protective layer of MgF2 was deposited in-situ onto the Er-doped glass films under the same CVD deposition conditions. The luminescence of Er around 1.55 micrometers was observed in films on all the substrates used. The emission line shapes are the same as those observed from Er-doped fluorozirconate glass. MOCVD proved to be a feasible technology to grow rare-earth doped fluoride films for planar waveguide devices. ©2004 Copyright SPIE - The International Society for Optical Engineering.
• Marder, S. R., Kippelen, B., Jen, A. K., & Peyghambarian, N. (1997). Design and synthesis of chromophores and polymers for electro-optic and photorefractive applications. Nature, 388(6645), 845-851.
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  Abstract: The ability of nonlinear optical materials to transmit, process and store information forms the basis of emerging optoelectronic and photonic technologies. Organic chromophore-containing polymers, in which the refractive index can be controlled by light or an electric field, are expected to play an important role.
• Meerholz, K., Bittner, R., Nardin, Y. D., Bräuchle, C., Hendrickx, E., Volodin, B. L., Kippelen, B., & Peyghambarian, N. (1997). Stability improvement of high-performance photorefractive polymers containing eutectic mixtures of electro-optic chromophores. Advanced Materials, 9(13), 1043-1046.
• Ohtsuki, T., Honkanen, S., Najafi, S. I., & Peyghambarian, N. (1997). Cooperative upconversion effects on the performance of Er³⁺-doped phosphate glass waveguide amplifiers. Journal of the Optical Society of America B: Optical Physics, 14(7), 1838-1845.
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  Abstract: The cooperative upconversion processes of erbium ions in silver film ion-exchanged waveguides in a phosphate glass were studied from the pump intensity dependence of luminescence decay curves. Cooperative upconversion coefficients of the 4I13/2 level, 7.7 ± 0.7 × 10-19 and 9.3 ± 0.7 × 10-19 cm3/s, were obtained for an Er3+ concentration of 1 × 1020 cm-3 in bulk and waveguide samples, respectively. These values are 1 order of magnitude smaller than the ones reported for silica glass. The increase in the cooperative upconversion coefficient with the increase in Er3+ concentration was found to be small. The effects of cooperative upconversion on the gain performance were analyzed for different Er3+ concentrations by a theoretical model based on experimentally measured gain with a 1.48-μm pump wavelength. Given the small cooperative upconversion coefficients in this glass, Er3+ concentrations potentially as high as 3.7 × 1020 cm-3 were shown to be feasible. Such high concentrations would result in a 12-dB gain at 150-mW pump power with a 4-cm-long waveguide. © 1997 Optical Society of America.
• Peyghambarian, N., & Kippelen, B. (1997). Advanced photorefractive and light-emitting organic materials. Materials Research Society Symposium - Proceedings, 488, 39-50.
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  Abstract: The tailoring of organic molecules and polymers has enabled the recent development of multifunctional materials such as photorefractive polymers and organic electroluminescent materials. This paper presents recent advances in both areas.
• Peyghambarian, N., & Kippelen, B. (1997). Photorefractive Polymers and Applications. Macromolecular Symposia, 116, 143-146.
• Sandalphon, ., Wang, J. F., Kippelen, B., & Peyghambarian, N. (1997). Optical dispersion of the refractive index modulation in low Tg photorefractive polymers. Applied Physics Letters, 71(7), 873-875.
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  Abstract: We measure at different wavelengths the linear and nonlinear optical properties of a new chromophore for photorefractive applications by means of frequency-dependent ellipsometry experiments. We show that the optical dispersion of the refractive index modulation responsible for the high diffraction efficiency in low Tg polymers can be described by a two-level model. © 1997 American Institute of Physics.
• Schuelzgen, A., Hughes, S., & Peyghambarian, N. (1997). Doppler-shifted self-reflected wave from a semiconductor. Proceedings of SPIE - The International Society for Optical Engineering, 2994, 393-399.
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  Abstract: We report the first experimental observation of a self- reflected wave inside a very dense saturable absorber. An intense femtosecond pulse saturates the absorption and causes a density front moving into the semiconductor sample. Due to the motion of the boundary between saturated and unsaturated areas of the sample the light reflected at this boundary is red-shifted by the Doppler effect. The spectrally shifted reflection makes it possible to distinguish between surface reflection and self-reflection and is used to proof the concept of the dynamic nonlinear skin effect experimentally. Quite well agreement with model calculations is found.
• Schulzgen, A., Hughes, S., & Peyghambarian, N. (1997). Observation of the dynamic nonlinear optical skin effect in a semiconductor. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 12, 219-220.
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  Abstract: A Doppler-shifted self-reflected wave is demonstrated through single beam reflection experiments and degenerated pump-probe reflection measurements. Using 150-fs pulses from the second harmonic of a modelocked Ti:sapphire laser, ZnSe is excited to resonant ground state exciton transition at 77 K. At low intensities the pronounced ground state exciton feature can be observed. The excitonic resonance disappears with increasing irradiance. However, the reflected pulse spectrum never resembles that of the incident pulse as it is expected for only stationary changes of the dielectric constant.
• Spiegelberg, C., Schulzgen, A., Morrell, M. M., Allemand, P. M., Kippelen, B., & Peyghambarian, N. (1997). Giant optical gain in conjugated polymers studied by femtosecond spectroscopy. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 11, 459-460.
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  Abstract: Advancement in the development of electroluminescent devices utilizes conjugated polymers as lasing materials. A polymer with stimulated emission and large optical gain was investigated. The photoluminescence was measured using a streak camera after passing through a monochromator. Pump-probe experiments with femtosecond pulses was conducted to study the dynamics of the absorption changes and the optical gain. The spectral shape of the time-integrated photoluminescence as a function of excitation intensity is presented. Doubling the excitation intensity results in an increase of the integrated emission by more than two orders of magnitude.
• Takahashi, M., Shojiya, M., Kanno, R., Kawamoto, Y., Kadono, K., Ohtsuki, T., & Peyghambarian, N. (1997). Nonradiative decay processes and mechanisms of frequency upconversion of Er³⁺ in ZrF₄-BaF₂-LaF₃ glass. Journal of Applied Physics, 81(7), 2940-2945.
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  Abstract: We have investigated the decay processes of the Er:4S3/2 and 4F9/2 states and the mechanisms of frequency upconversion under 800 nm excitation of Er3+ in ternary ZrF4-BaF2-LaF3 glasses. The decay processes of the Er:4S3/2 and 4F9/2 states are discussed on the basis of the Er concentration dependence of the fluorescence lifetime. The quantum efficiencies of emission of the 4S3/2 and 4F9/2 states are 73% and 25%, respectively. The difference in the quantum efficiencies between these states can be explained from the difference in the multiphonon decay rates: the multiphonon decay rate of the 4S3/2 state is much smaller than that of the 4F9/2 state. The multiphonon relaxation is a dominant nonradiative decay process of the 4F9/2 state. A dominant nonradiative decay process of the 4S3/2 state is self-quenching at high Er concentrations. The upconversion mechanisms under 800 nm excitation are also investigated from the dependence of upconversion luminescence on excitation wavelengths (800 and 980 nm). excitation laser power, and Er concentration. The mechanism of upconversion from 800 to 660 nm is mainly due to the energy transfer between the 4I9/2→4I13/2 and 4F9/2←4I11/2 transitions. We also show that the upconversion from 800 to 550 nm is due to excited-state absorption. © 1997 American Institute of Physics.
• Talanina, I., Binder, R., Burak, D., Peyghambarian, N., & Giessen, H. (1997). Soliton model for propagation of subpicosecond light pulses interacting with Wannier excitons. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 12, 192-.
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  Abstract: Light pulse propagation with excitonic nonlinearities was investigated, analytically and numerically and compared with two related phenomena: self-induced transparency in atomic systems and femtosecond soliton propagation in Kerr media. For resonant excitation at the s-exciton resonance, the light-matter interaction can be described by reduced semiconductor Maxwell-Bloch equations for the electric field of light and induced excitonic polarization. The model assumes a large exciton binding energy thus allowing higher exciton and continuum states to be neglected. For femtosecond light pulses with moderate intensities, the observed effect justifies the neglect of the screening.
• Vacar, D., Heeger, A. J., Volodin, B., Kippelen, B., & Peyghambarian, N. (1997). Compact, low power polymer-based optical correlator. Review of Scientific Instruments, 68(2), 1119-1129.
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  Abstract: A low cost, low power compact optical correlator is demonstrated. It operates interchangeably in the matched-filter or joint-transform configurations. The active medium is a high diffraction efficiency photorefractive host-guest polymer system. Successful image correlation has been achieved. © 1997 American Institute of Physics.
• Volodin, B. L., Steele, D. D., Kippelen, B., & Peyghambarian, N. (1997). Imaging through scattering media with used of photorefractive polymers. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 11, 184-185.
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  Abstract: Imaging through a scattering medium via a holographic time gating is demonstrated using a photorefractive polymer. In this method a hologram is formed by the temporal overlap of the reference and the first arriving light from the stretched image-bearing pulse in the photorefractive polymer. The filtering is thus achieved in real time without any need for digital processing. The image carried by the ballistic light can then be reconstructed in real time via diffraction of a probe beam.
• Wang, J. F., Nabor, M. F., Kawabe, Y., Shaheen, S. E., Morrell, M. M., Kippelen, B., & Peyghambarian, N. (1997). High-brightness organic LEDs based on a new electron transporting material and a dopant in emission layer. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 11, 174-175.
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  Abstract: A quinoxaline derivative with good performance is developed as an electron transporter in blue and green high-brightness organic light emitting diode (LED) devices. These compounds may yield higher performance by optimizing their combination with emission layer. The performance of the organic LED based on a newly developed quinoxaline derivative with electron transport ability and a quinacridone derivative doped in AlQ3 are discussed.
• Yuhuan, X. u., Kao, Y., Chia, C., Mackenzie, J. D., Honkanen, S., & Peyghambarian, N. (1997). Optical waveguide based on CdS quantum dot-doped sodium borosilicate glass fabricated by the sol-gel technique. Proceedings of SPIE - The International Society for Optical Engineering, 3136, 326-336.
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  Abstract: Semiconductor CdS quantum dot-doped sodium borosilicate glasses were successfully fabricated by the sol-gel technique. The dot size and concentration of CdS are controlled by chemistry and processing conditions. Optical absorption spectra were measured for these quantum dot-doped glasses, and absorption shoulder due to the exciton effect was observed. Nonlinear optical properties of high third-order susceptibility, χ(3), and room-temperature optical gain were observed. Potassium ion exchange was performed on the glass, and channel waveguides were successfully fabricated in the CdS-doped glass. The wavegide was tested with single mode laser pulses, and single mode output was demonstrated. Spectral broadening of the output pulses was observed.
• Araujo, R. J., Butty, J., & Peyghambarian, N. (1996). Optical properties of glasses containing copper oxide particles. Applied Physics Letters, 68(5), 584-586.
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  Abstract: Particles of cuprous oxide with 20 nm sizes have been precipitated from borosilicate glasses. The absorption spectra show distinct changes in glasses given different heat treatments. Only very weak nonlinear effects are observed. © 1996 American Institute of Physics.
• Ashley, P., Jen, A., Lindsay, G., Miller, R., Peyghambarian, N., Steier, W., & Lytel, R. (1996). Electro-optic polymers [2]. Chemical and Engineering News, 74(32), 2+37+47.
• Butty, J., Jabbour, G. E., Mohs, G., Fluegel, B. D., Peyghambarian, N., Kao, Y. H., & Mackenzie, J. D. (1996). Optical gain and radiative decay dynamics in sol-gel-derived CdS quantum dots. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 474-475.
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  Abstract: Optical gain measurements in quantum dots (QDs) with nanosecond nonresonant excitation are carried out using the variable-stripe-length method. In particular, the photoluminescence (PL) decay dynamics is investigated using femtosecond excitation at 310 nm and streak camera detection. The emission displays two bands as it is usually observed in the semiconductor-doped glasses.
• Butty, J., Jabbour, G. E., Tajalli, H., Peyghambarian, N., & Borrelli, N. F. (1996). Absorption saturation in PbS-quantum dots. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 475-.
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  Abstract: PbS is an attractive semiconductor for the fabrication of quantum dots (QDs) because of its large bulk Borh exciton radius (18 nm). The features of PbS are confirmed by conducting absorption saturation measurements in different PbS-doped glasses at room temperature. With a modest energy and fast response time, large absorption change emerged. This result is encouraging for possible applications of PbS QDs as passive Q-switch or optical modulator.
• Butty, J., Peyghambarian, N., Kao, Y. H., & Mackenzie, J. D. (1996). Room temperature optical gain in sol-gel derived CdS quantum dots. Applied Physics Letters, 69(21), 3224-3226.
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  Abstract: Under strong nanosecond excitation, we demonstrate that II-VI semiconductor quantum dots exhibit optical gain up to room temperature. The CdS nanocrystallites, fabricated by sol-gel process, are embedded in a sodium borosilicate glass matrix. The gain is spectrally broad and the crossing between absorption and gain is well above the bulk absorption band edge energy, since our nanocrystallites are in the intermediate quantum confinement regime. The gain has a long tail extending to the low energy side of the absorption edge. This tail was shown theoretically to originate from the multiple excited states involved in the recombination between two and one electron-hole pairs. © 1996 American Institute of Physics.
• Coudray, P., Chisham, J., Malek-Tabrizi, A., Li, C. -., Andrews, M. P., Peyghambarian, N., & Najafi, S. I. (1996). Ultraviolet light imprinted sol-gel silica glass waveguide devices on silicon. Optics Communications, 128(1-3), 19-22.
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  Abstract: We describe a new simplified process for inexpensive fabrication of low-loss (0.1 dB/cm) glass waveguides on silicon by ultraviolet light imprinting in photosensitive, organically modified sol-gel silica glass films prepared by one-step dip-coating process. The fabrication process is appealing because the buffer layer between waveguide and substrate is eliminated, and waveguides can be made in a few steps using low-cost equipment. Also, a 1 × 8 power splitter is produced by this process. The splitter exhibits relatively uniform output and a configuration loss of 0.9 dB at 1.55 μm wavelength.
• Giessen, H., Fluegel, B., Mohs, G., Hu, Y. Z., Peyghambarian, N., Woggon, U., Klingshirn, C., Thomas, P., & Koch, S. W. (1996). Dephasing in the gain region of II-VI semiconductor nanocrystals. Journal of the Optical Society of America B: Optical Physics, 13(5), 1039-1044.
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  Abstract: We investigate the dephasing times in highly excited CdSe and CdS0.3Se0.7 nanocrystals by spectral hole burning throughout the gain region. The energy dependence of the dephasing time T2 is compared between quantum dots in the strong-confinement regime and bulklike microcrystals. T2 in strongly confined quantum dots remains rather constant, whereas the bulklike sample shows a continuous increase of T2 toward the transparency point. This observation is attributed to the different gain mechanisms in the strong and the weak quantum-confinement regimes. © 1996 Optical Society of America.
• Giessen, H., Fluegel, B., Mohs, G., Peyghambarian, N., Sprague, J. R., Micic, O. I., & Nozik, A. J. (1996). Observation of the quantum confined ground state in InP quantum dots at 300 K. Applied Physics Letters, 68(3), 304-306.
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  Abstract: Colloidal suspensions of InP quantum dots (diameters 25 and 35 Å) show steplike absorption spectra which are blue-shifted by about 1 eV with respect to bulk material. Time resolved femtosecond spectroscopy at room temperature identifies the first quantum confined state. The nonlinear bleaching signal rises within 300 fs and persists longer than 200 ps. © 1996 American Institute of Physics.
• Giessen, H., Woggon, U., Fluegel, B., Mohs, G., Hu, Y. Z., Koch, S. W., & Peyghambarian, N. (1996). Femtosecond optical gain in strongly confined quantum dots. Optics Letters, 21(14), 1043-1045.
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  PMID: 19876246;Abstract: Optical gain was found in strongly confined CdSe quantum dots. As a result of a multitude of one- and two-electron-hole pair transitions, the gain region is broad and quasi-continuous and stretches below the absorption edge. We present a model for gain in a quasi-zero-dimensional quantum confined semiconductor system that agrees well with the femtosecond experiments. © 1996 Optical Society of America.
• Giessen, H., Woggon, U., Fluegel, B., Mohs, G., Hu, Y. Z., Koch, S. W., & Peyghambarian, N. (1996). Quantum dots in the strong confinement regime: A model system for gain in quasi zero-dimensional semiconductors. Chemical Physics, 210(1-2 SPEC. ISS.), 71-78.
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  Abstract: We present a model for gain in a quasi zero-dimensional quantum confined semiconductor system. Due to a combination of a multitude of one-electron-hole pair and two-electron-hole pair transitions and inhomogeneous broadening, the gain region is broad, quasi-continuous and stretches below the absorption edge. Femtosecond experiments in the gain region of strongly confined CdSe quantum dots confirm our theoretical predictions.
• Giessen, H., Woggon, U., Fluegel, B., Mohs, G., Hu, Y. Z., Koch, S. W., & Peyghambarian, N. (1996). Quantum dots in the strong confinement regime: a model system for gain in quasi-zero-dimensional semiconductors. Proceedings of SPIE - The International Society for Optical Engineering, 2693, 233-237.
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  Abstract: We present a model for gain in a quasi zero-dimensional quantum confined semiconductor system. Due to a multitude of one-electron-hole pair and two-electron-hole pair transitions, the gain region is broad, quasi-continuous and stretches below the absorption edge. Femtosecond experiments in the gain region of strongly confined CdSe quantum dots confirm our theoretical predictions.
• Hu, Y. Z., Gießen, H., Peyghambarian, N., & Koch, S. W. (1996). Microscopic theory of optical gain in small semiconductor quantum dots. Physical Review B - Condensed Matter and Materials Physics, 53(8), 4814-4822.
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  Abstract: A microscopic theory is used to analyze optical gain in small semiconductor quantum dots. Based on a numerical matrix diagonalization method and subsequent solution of the optical Bloch equations, it is found that the quantum-dot gain is dominated by the stimulated transitions between biexciton and exciton states. The calculation shows that Coulomb interaction and valence-band mixing effects significantly influence the spectral and dynamic gain properties in strongly confined quantum dots.
• Hu, Y. Z., Koch, S. W., & Peyghambarian, N. (1996). Strongly confined semiconductor quantum dots: Pair excitations and optical properties. Journal of Luminescence, 70(1-6 SPEC. ISS.), 185-202.
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  Abstract: This paper reviews a microscopic model of basic electron hole pair excitation processes in strongly confined semiconductor quantum dots (QD) and their influence on the optical QD properties. The effects of valence band mixing, Coulomb interaction, and surface polarization are taken into account. The exciton and biexciton wave functions and energies are obtained using a numerical diagonalization method. The computed optical spectra, such as absorption, gain, pump-probe, and two-photon absorption, agree well with experiments.
• Javidi, B., Kippelen, B., & Peyghambarian, N. (1996). Optical processing system can foil counterfeiters. Laser Focus World, 32(10), 75-81.
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  Abstract: Phase/amplitude patterns read by an optical correlator promise a virtually foolproof credit-card security verification system.
• Jiang, S., Myers, M., & Peyghambarian, N. (1996). Section 3. Laser and amplifier glasses and glass-ceramics: Er³⁺ doped phosphate glasses and lasers. Journal of Alloys and Compounds, 239(1), 143-148.
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  Abstract: Phosphate glass samples with various Cr2O3, Yb2O3, and Er2O3 contents based upon 67P2O5·14Al2O 3·14Li2O·1K2O·4(Yb 2O3 + Er2O3) were prepared. The effect of changing concentrations of Er3+ ions (0.1-1.5 × 1019 ions cm-3) and sensitizers Cr3+ ion and Yb3+ ion (2-16 × 1018 ions cm-3 and 1.35-2.3 × 1021 ions cm-3 respectively) on laser performance were investigated. The thermal shock resistance of this glass was doubled after an ion-exchange chemical strengthening process in a KNO3/NaNO3 molten salt bath. Lasers with repetition rates of 20 Hz at free-running and 15 Hz at Q-switched single mode were demonstrated by utilizing chemically strengthened laser glass rods. © 1998 Elsevier Science B.V. All rights reserved.
• Kippelen, B., Meerholz, K., Sandalphon, ., Volodin, B. L., & Peyghambarian, N. (1996). Photorefractive polymers and their applications. Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals, 283, 109-114.
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  Abstract: We review the basic properties of photorefractive polymer composites and discuss the performance of low glass-transition guest/host type polymers. Examples of applications using these new materials are presented.
• Kippelen, B., Sandalphon, ., Meerholz, K., & Peyghambarian, N. (1996). Birefringence, Pockels, and Kerr effects in photorefractive polymers. Applied Physics Letters, 68(13), 1748-1750.
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  Abstract: A simple frequency-dependent ellipsometric technique for measuring the birefringence, the Pockels and Kerr properties of low glass-transition temperature photorefractive polymers is proposed. The technique is applied to the characterization of highly efficient DMNPAA:PVK:ECZ:TNF photorefractive polymers and the determination of the microscopic properties of the DMNPAA molecule. © 1996 American Institute of Physics.
• Kippelen, B., Shaheen, S. E., Morrell, M. M., Guerreiro, P. T., Peyghambarian, N., & Allemand, P. M. (1996). Electroluminescence in an organic polymer channel waveguide. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 88-.
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  Abstract: This paper demonstrates the fabrication of a channel-waveguide structure with an organic electroluminescent thin film. It shows electroluminescence in layers that are thick enough to support confined waveguide modes by applying somewhat higher voltages (20-30 V) compared with thin-film surface-emitting devices (
• Kippelen, S. B., Meerholz, K., & Peyghambarian, N. (1996). Ellipsometric measurements of poling birefringence, the Pockels effect, and the Kerr effect in high-performance photorefractive polymer composites. Applied Optics, 35(14), 2346-2354.
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  Abstract: Using a simple ellipsometric technique, we measure the total refractive-index modulation as a function of the frequency of the applied electric field in low glass-transition-temperature photorefractive polymer composites. From these measurements we deduce the relative contributions of the poling birefringence and the Pockels and Kerr effects. By applying the oriented gas model we determine the microscopic properties of the nonlinear optical chromophore, including the anisotropic polarizability, and the first and the second hyperpolarizabilities. In the search for new high-performance materials, the technique provides a measure of the linear and the second- and third-order nonlinear optical properties simultaneously. © 1996 Optical Society of America.
• Kippelen, S. B., Meerholz, K., & Peyghambarian, N. (1996). Simultaneous determination of first-, second-, and third-order nonlinear optical properties of photorefractive polymers. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 16-.
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  Abstract: Using the variable-frequency ellipsometric technique. This paper measures the total refractive index modulation as a function of the frequency of the applied electric field. From these measurements. It deduces the relative contributions of the poling birefringence, the Pockels, and the Kerr effects. By applying the oriented gas model, it determines the microscopic properties of the nonlinear optical chromophore, including the anisotropic polarizability, and the first and second hyperpolarizabilities.
• Meerholz, K., Bittner, R., Brauchle, C., Volodin, B. L., Sandalphon, ., Kippelen, B., & Peyghambarian, N. (1996). Improved long-term stability of high-performance photorefractive polymer devices. Proceedings of SPIE - The International Society for Optical Engineering, 2850, 100-107.
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  Abstract: We report on novel high-performance photorefractive polymer composites based on poly(N-vinylcarbazole) using mixtures of two isomeric electro-optically active chromophores. We demonstrate that the shelf life time of devices using the eutectic mixture is considerably improved compared with devices containing just one isomer.
• Meerholz, K., Volodin, S. B., Kippelen, B., & Peyghambarian, N. (1996). Improved stability of photorefractive polymer composites by use of eutectic mixture of EO chromophores. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 477-478.
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  Abstract: A new unique way is proposed to improve the shelf-life time of current PR (organic photorefractive) polymer devices using mixtures of two isomeric electro-optically (EO) active chromophores. Because 2,5DMNPAA has proven to exhibit excellent PR performance, the isomer with 3,5-dimethyl substitution is additionally chosen.
• Mohs, G., Binder, R. H., Fluegel, B., Giessen, H., & Peyghambarian, N. (1996). Observation of spectral hole sidebands in the gain region of an inverted semiconductor. Proceedings of SPIE - The International Society for Optical Engineering, 2693, 274-281.
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  Abstract: We have performed ultrafast three-pulse experiments in order to investigate the relaxation of charge carriers from a non-equilibrium distribution in inverted GaAs multiple quantum wells. The first pulse, used to create optical gain, was followed by a conventional pump-probe study. The pump-induced spectral hole inside the optical gain was accompanied by sidebands which occurred about 39 meV above the original spectral hole. These sidebands can be explained in terms of LO-phonon scattering of the charge carriers into the vacancies of the spectral hole.
• Mohs, G., Binder, R., Fluegel, B., Giessen, H., & Peyghambarian, N. (1996). Phonon emission by nonequilibrium carriers in the gain region of an inverted semiconductor. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 9, 158-159.
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  Abstract: Carrier relaxation dynamics in the gain region of semiconductors are of interest not only from a fundamental point of view but also with respect to the basic limits of semiconductor lasers and optical amplifiers. Of particular importance are relaxation effects resulting from carrier-phonon scattering. This paper focus on the emission of LO-phonons by charge-carriers in a nonequilibrium distribution. The nonequilibrium distribution is generated in a cool electron hole plasma by spectral hole burning.
• Mohs, G., Binder, R., Fluegel, B., Gießen, H., & Peyghambarian, N. (1996). Phonon-induced spectral holes in the gain region of an inverted semiconductor. Journal of the Optical Society of America B: Optical Physics, 13(6), 1298-1301.
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  Abstract: Spectral-hole-burning experiments are performed in the gain region of an inverted semiconductor multiple quantum well. We find not only a spectral hole at the pump-pulse frequency but also replicas at higher frequencies. These replicas are qualitatively explained in terms of carrier-phonon interactions in which high-energy carriers relax into the optically induced spectral hole by LO-phonon emission. © 1996 Optical Society of America.
• Murray, J. T., Bonilla, S., Jiang, J. P., Tajalli, H., Powell, R. C., & Peyghambarian, N. (1996). Determination of nonlinear susceptibilities by transforming random variables. Journal of Applied Physics, 79(9), 6735-6740.
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  Abstract: High-peak-power lasers are typically used as pump sources in nonlinear optical measurements. Intrinsic to these sources are pulse-to-pulse output energy instabilities. We report on how pump instabilities affect the measurement of nonlinear susceptabilites and develop theory which relates statistical parameters of a general, arbitrary pump energy probability distribution to those of its corresponding mth harmonic output. The relation leads to a simple method of data analysis whereby pump instabilities can be used as a tool in determining the nonlinear susceptibility of a material. © 1996 American Institute of Physics.
• Murray, J. T., Powell, R. C., Peyghambarian, N., & Austin, W. L. (1996). Solid-state Raman lasers. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 316-317.
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  Abstract: Over the past few years there has been actively significant effects of novel intracavity solid-state Raman lasers high brightness sources to be utilized by the remote sensing and adaptive optics communities. Intracavity solid state Raman lasers offer an elegant means of efficiently generating high average power near diffraction limited pulse compressed emission in useful spectral regions. This review focuses on spatial, temporal and spectral characteristics of high average power intracavity solid-state Raman lasers as well as recently developed design and modelling techniques. Experimental results of Raman lasers as well as recently developed design and modelling techniques. Experimental results of Raman lasers are presented.
• Najafi, S., Li, C. -., Chisham, J. E., Andrews, M. P., Coudray, P., Malek-Tabrizi, A., & Peyghambarian, N. (1996). Ultraviolet-light-imprinted sol-gel silica glass channel waveguides on silicon. Proceedings of SPIE - The International Society for Optical Engineering, 2695, 38-41.
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  Abstract: We describe a new simplified process for inexpensive fabrication of low-loss (0.1 dB/cm) glass waveguides on silicon by ultraviolet light imprinting in photosensitive, organically modified sol-gel silica glass films prepared by one-step dip-coating process. The fabrication process is appealing because the buffer layer between waveguide and substrate is eliminated, and waveguides can be made in a few steps using low-cost equipment.
• Ohtsuki, T., Honkanen, S., Ingenhoff, J., Heyden, J., Fabricius, N., Najafi, S. I., & Peyghambarian, N. (1996). Polarization-insensitive planar glass waveguide amplifiers by silver ion exchange. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 462-463.
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  Abstract: This research focuses on waveguide amplifiers suitable for a number of applications. A silver-ion-exchange technique in waveguide fabrication is used which results in low birefringent waveguides. Two different erbium-doped glasses, a commercial phosphate laser glass developed for silver ion exchange are used as substrates. Finally, the small signal gain of these waveguides is measured by a pump and probe technique using a pump wavelength of 1.48 μm from a Cr:YAG laser.
• Ohtsuki, T., Honkanen, S., Peyghambarian, N., Takahashi, M., Kawamoto, Y., Ingenhoff, J., Tervonen, A., & Kadono, K. (1996). Evanescent-field amplification in Nd³⁺-doped fluoride planar waveguide. Applied Physics Letters, 69(14), 2012-2014.
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  Abstract: Planar channel waveguides of rare-earth doped fluoride glass are demonstrated with single mode excitation and propagation losses below 3 dB/cm. The waveguide core was fabricated by Ag+-Na+ molten salt ion exchange process in a borosilicate glass (BGG31), and a Nd3+-doped ZBLAN glass was used as a cladding. A 0.45 dB signal amplification at 1.064 μm was observed in the fabricated 1 cm long waveguide, and a 0.9 dB amplification is expected at the emission peak (1.049 μm). Modeling results show 2.5 dB/cm potential gain with the improvement in surface flatness of ZBLAN glass. © 1996 American Institute of Physics.
• Park, S. S., Mackenzie, J. D., Li, C. Y., Guerreiro, P., & Peyghambarian, N. (1996). Fiber optic sensing of cyanides in solutions. Materials Research Society Symposium - Proceedings, 435, 667-672.
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  Abstract: A novel sol-gel technique was used to immobilize malachite green ions (MG+) in stable, optically transparent, porous silica gel films. A simple and sensitive method was developed for the detection of cyanides in solutions using spectrophotometry to measure changes caused by cyanide ions (CN-) in the absorption spectra of the green-colored silica gel films. After reaction with cyanide ions, the absorption spectra of the films changed with a typical decrease in absorbance at 620 nm. On the basis of the absorption spectra of the films, a portable and easy to use fiber optic cyanide film sensor was fabricated. Decolorization undergone by the green-colored gel films, as they were exposed to cyanide ions, was detected through a fiber. Preliminary results indicate concentrations on the order of a few ppm are detected using the fiber optic sensor.
• Peyghambarian, N., & Kippelen, B. (1996). New stack system for records. Nature, 383(6600), 481-.
• Takada, T., Mackenzie, J. D., Yamane, M., Kang, K., Peyghambarian, N., Reeves, R. J., Knobbe, E. T., & Powell, R. C. (1996). Preparation and non-linear optical properties of CdS quantum dots in Na₂O-B₂O₃-SiO₂ glasses by the sol-gel technique. Journal of Materials Science, 31(2), 423-430.
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  Abstract: Non-linear optical properties of CdS quantum dots embedded in the sol-gel derived Na2O-B2O3-SiO2 glass matrix have been studied using nanosecond degenerate four-wave mixing (DFWM), pump-probe experiments, and time-resolved subpicosecond DFWM measurements. The concentration of CdS microcrystallites was varied from 1.4 to 10.2 wt% while the particle size was controlled to be in the range of 36 nm in diameter so that the confinement effects can be realized. The third-order susceptibility, χ(3), was determined to be of the order of 10-7-10-6 e.s.u. near the resonant wavelength between 450 and 470 nm by the nanosecond DFWM and pump-probe experiments, and of the order of 10-11-10-10 e.s.u. at the off-resonant wavelength, 580 nm, by a time-resolved DFWM measurement with 400 fs laser pulse. The decay time changed from 0.5 to 50 picoseconds as a function of the size, size distribution and number density of CdS microcrystallites in the glasses. Photodarkerting reduced the optical non-linearity of the melt-quenched samples by a factor of ≈ 20, while it had no appreciable effect on that of the sol-gel derived samples. © 1996 Chapman & Hall.
• Ten, S. Y., Henneberger, F., Rabe, M., & Peyghambarian, N. (1996). Exciton tunneling in wide-bandgap semiconductors. Proceedings of SPIE - The International Society for Optical Engineering, 2693, 315-321.
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  Abstract: We have studied exciton tunneling in (Zn,Cd)Se/ZnSe asymmetric double quantum wells using femtosecond time resolved transmission, photoluminescence and time-resolved photoluminescence measurements. The strong Coulomb correlation as well as Frohlich electron LO-phonon interaction in II-VI semiconductors make the tunneling process significantly different from that in III-VI structures. We observe fast (1 ps) exciton tunneling out of the narrow well, although LO-phonon scattering is forbidden for holes in a single- particle picture. However, our theoretical analysis shows that tunneling of the exciton as a whole entity with the emission of only one LO-phonon is very slow. Instead, the exciton tunnels via an indirect state in a two-step process whose efficiency is dramatically enhanced by Coulomb effects.
• Ten, S., Henneberger, F., Rabe, M., & Peyghambarian, N. (1996). Exciton tunneling in (Zn, Cd)Se/ZnSe asymmetric double quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 9, 1pp.
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  Abstract: Presented is an investigation of exciton tunneling in a (Zn, Cd)Se/ZnSe asymmetric double quantum wells (ADQW) structure. The five period (Zn, Cd)Se/ZnSe ADQW sample was grown by molecular beam epitaxy on an undoped GaAs substrate. A single ADQW consists of a Zn0.82Cd0.18Se 13-angstrom narrow well (NW) and 25-angstrom wide well (WW) separated by a 42-angstrom ZnSe barrier. The time-resolved transmission setup utilized frequency doubled optical pulses generated by a self-modelocked femtosecond Ti:sapphire laser. Pump and probe were tuned to the NW heavy-hole exciton resonance and differential transmission was recorded.
• Ten, S., Henneberger, F., Rabe, M., & Peyghambarian, N. (1996). Femtosecond study of exciton tunneling in (Zn,Cd)Se/ZnSe asymmetric double quantum wells. Physical Review B - Condensed Matter and Materials Physics, 53(19), 12637-12640.
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  Abstract: We have studied, both experimentally and theoretically, exciton tunneling in a (Zn,Cd)Se/ZnSe asymmetric double quantum-well structure. The large exciton binding energy of these structures allows us to elucidate the role of the electron-hole interaction. Subsequent to resonant femtosecond pulse excitation, we observe fast (1 ps) exciton tunneling out of the narrow well, although LO-phonon scattering is forbidden for holes in a single-particle picture. Our theoretical analysis shows, however, that tunneling of the exciton as a whole entity with the emission of only one LO phonon is very slow. Instead, the exciton tunnels via an indirect state in a two-step process whose efficiency is dramatically enhanced by Coulomb effects.
• Ten, S., Krol, M. F., Guerreiro, P. T., & Peyghambarian, N. (1996). Ultrafast electron and hole tunneling in (Ga,In)As/(Al,In)As asymmetric double quantum wells. Applied Physics Letters, 69(22), 3387-3389.
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  Abstract: We present unambiguous experimental evidence for the dramatic dependence of hole tunneling rates on in-plane momentum in (Ga,In)As/(Al,In)As asymmetric double quantum wells. Holes generated near the band edge tunnel on hundred picosecond time scales, whereas holes excited with large excess energy tunnel on subpicosecond time scales. The mechanism responsible for this increase of more than three orders of magnitude in the hole tunneling rate is nonresonant delocalization of hole wave functions by band mixing in the valence band. © 1996 American Institute of Physics.
• Volodin, B. L., Kippelen, B., Meerholz, K., Javidi, B., & Peyghambarian, N. (1996). A polymeric optical pattern-recognition system for security verification. Nature, 383(6595), 58-60.
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  Abstract: Polymers that exhibit the photorefractive effect - a light-induced modulation of refractive index-are emerging as attractive materials for optical devices and processing systems. Here we demonstrate one such application using our recently developed high-efficiency photorefractive polymer. The polymer provides a nonlinear medium in which real-time all- optical image correlation, and hence pattern recognition, can be accomplished. This forms the basis of an optical security system, whereby documents are encoded with practically invisible phase masks (such masks are difficult to forge), which may then be rapidly screened to verify the authenticity of the documents. The wavelengths at which our optical system operates are compatible with commercial low-power semiconductor loser diodes, and the system can be integrated into a compact device at low cost.
• Volodin, B. L., Kippelen, B., Meerholz, K., Kukhtarev, N. V., Caulfield, H. J., & Peyghambarian, N. (1996). Non-Bragg orders in dynamic self-diffraction on thick phase gratings in a photorefractive polymer. Optics Letters, 21(7), 519-521.
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  PMID: 19865458;Abstract: We demonstrate that recording thick holographic phase gratings in photorefractive polymers can lead not only to very efficient Bragg diffraction but also to rather strong diffraction into non-Bragg orders. We show that this effect has features drastically different from those of Raman-Nath diffraction on thin gratings. We compare the experimental results with a model based on the theory of dynamic self-diffraction in a photorefractive medium. Applications of this effect in devices for optical image processing are proposed. © 1996 Optical Society of America.
• Volodin, B. L., Kippelen, B., Meerholz, K., Peyghambarian, N., Kukhtarev, N. V., & Caulfield, H. J. (1996). Non-Bragg diffraction orders in highly efficient photorefractive polymers. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 257-.
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  Abstract: This report presents the first observation of strong non-Bragg diffraction orders in photorefractive polymers. It is shown that these non-Bragg diffraction orders offer new opportunities to implement wavefront transformations on interacting beams in a photorefractive polymer in a two-beam geometry as opposed to the standard four-wave mixing geometry.
• Volodin, B. L., Kippelen, B., Meerholz, K., Peyghambarian, N., Kukhtarev, N. V., & Caulfield, H. J. (1996). Study of non-Bragg orders in dynamic self-diffraction in a photorefractive polymer: Experiment, theory, and applications. Journal of the Optical Society of America B: Optical Physics, 13(10), 2261-2267.
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  Abstract: We present a consistent experimental and theoretical study of non-Bragg orders observed in dynamic selfdiffraction on thick phase holograms in a photorefractive polymer that showed a strong refractive-index modulation amplitude. We demonstrate experimentally how the diffraction into non-Bragg orders can be used for image processing and as an independent evaluation method for the optical-photorefractive properties of the polymers. © 1996 Optical Society of America.
• Volodin, B. L., Kippelen, B., Peyghambarian, N., & Javidi, B. (1996). Optical correlator using photorefractive polymers for credit card validation. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 166-167.
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  Abstract: Using optical phase masks is a promising solution for validation of a credit cards and other documents authenticity. These masks placed on a document are invisible to the eye and, as such, are impossible to reproduce by any photographic process. They can be manufactured of transparent durable plastics and identified by an optical correlator using efficient photorefractive polymers as nonlinear material, as demonstrated in this paper. The entire system employs plastics and laser diodes for its operation and thus can be very compact and inexpensive to implement. The experimental demonstration using this method is presented and discussed.
• Woggon, U., Giessen, H., Gindele, F., Wind, O., Fluegel, B., & Peyghambarian, N. (1996). Ultrafast energy relaxation in quantum dots. Physical Review B-Condensed Matter, 54(24), 17681-17690.
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  Abstract: By use of femtosecond differential absorption spectroscopy the electron-hole pair relaxation times have been determined in CdSe quantum dots with excited state energies larger than the LO-phonon energy. The fast energy relaxation within 500 fs is independent of the relation between level spacing and LO-phonon energy and shows no bottleneck effect. The population dynamics is mainly governed by the hole relaxation process. With increasing intensity, the formation of two-pair states (biexcitons) of various energies dominates the population dynamics due to the strong influence of Coulomb interaction in quantum dots even in the strong confinement. At high pair densities, the created two-pair states mediate a new relaxation path due to their stimulated decay into one photon and one electron-hole pair with lower energy. © 1996 The American Physical Society.
• Araujo, R. J., Butty, J., & Peyghambarian, N. (1995). Optical properties of glasses containing copper oxide particles. Applied Physics Letters, 584-.
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  Abstract: Particles of cuprous oxide with 20 nm sizes have been precipitated from borosilicate glasses. The absorption spectra show distinct changes in glasses given different heat treatments. Only very weak nonlinear effects are observed. © 1996 American Institute of Physics.
• Butty, J., Hu, Y. Z., Peyghambarian, N., Kao, Y. H., & Mackenzie, J. D. (1995). Quasicontinuous gain in sol-gel derived CdS quantum dots. Applied Physics Letters, 67, 2672-.
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  Abstract: We report evidence for quasicontinuous optical gain in CdS quantum dots fabricated by the sol-gel process and embedded in glass. The gain spectra are obtained using the pump and probe technique and nanosecond (quasiresonant) excitation at 11 K. The dots are in the intermediate quantum confinement regime and the concentration of CdS is relatively high. The gain, which is spectrally broad, develops on the low energy side of the absorption band edge. The reason why the gain region is broad is not only the size distribution of the dots, but also the nature of the gain, which originates from the recombination of several excited levels between two and one electron-hole pairs states (i.e., biexciton to exciton). The maximum measured gain reaches 200cm-1 at 11 K and 17cm-1 at 170 K.© 1995 American Institute of Physics.
• Eliseev, P. G., Osinski, M., Phillips, B., Chiu, P., Mohs, G., Fluegel, B., Giessen, H., & Peyghambarian, N. (1995). Impurity-related photoluminescence from InGaN led material. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 2, 104-105.
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  Abstract: This paper explains the quantitative nature of the major emission band in Nichia's LEDs, namely InGaN/AlGaN/GaN high-brightness blue LEDs which represent a major breakthrough in short-wavelength visible light sources. The experimental low-temperature and room-temperature spectra are obtained by photoluminescence. A broad impurity-related PL band, with an undulated envelope centered at approx.465 nm, is observed at both temperatures when the pump beam illuminates the active region. In contrast, when the pump beam illuminates the GaN region under the n-side contact, only a weak yellow emission, centered at approx.560 n is observed. The room temperature blue spectral band is very similar to the electroluminescence spectrum. Concludingly, it is emitted from the active region of the diode, intentionally doped with Zn acceptors and heavily doped with Si donors. The active region may also contain some native donor-type defects usually present in group-III nitrides. In the interpretation of the blue emission band, all of these impurity levels are invoked.
• Francois, V., Ohtsuki, T., Peyghambarian, N., & Najafi, S. (1995). Fabrication and characterization of ion-exchanged neodymium-doped glass waveguide lasers. Proceedings of SPIE - The International Society for Optical Engineering, 2401, 176-181.
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  Abstract: We report on fabrication and characterization of channel waveguide lasers, operating near 1.06 μm and made in a commercial neodymium-doped glass using thermal silver ion exchange. The slope efficiency and threshold are measured as a function of waveguide width. The waveguide structure with a 7.5 μm width shows the best laser characteristics in terms of threshold and slope efficiency. The emitted wavelength, while close to the peak emission wavelength of the bulk glass at 1.059 μm, varies with the waveguide width. This behavior is interpreted in terms of the birefringence and the dichroism of the waveguides.
• Francois, V., Ohtsuki, T., Peyghambarian, N., & Najafi, S. (1995). Length optimization of single-mode rare-earth doped waveguides using saturated absorption. IEEE Photonics Technology Letters, 7(8), 872-874.
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  Abstract: Absorption saturation was demonstrated to provide a high, uniform population inversion over a length of waveguide longer than the material absorption length. The small signal gain was measured experimentally in single-mode waveguides, made by silver ion exchange, on a commercially available neodymium doped glass. The ratio of the excited states was calculated as a function of waveguide length and was shown to be a convenient criteria to determine the optimum device length.
• François, V., Ohtsuki, T., Peyghambarian, N., & Najafi, S. (1995). Thermally silver ion exchanged integrated-optic lasers in neodymium-doped silicate glass. Optics Communications, 119(1-2), 104-108.
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  Abstract: Continuous-wave integrated-optic channel waveguide lasers operating near 1.06 μm have been fabricated by thermal silver ion exchange in a commercial neodymium-doped glass. The laser slope efficiency and threshold as a function of waveguide width are measured. The laser output wavelength is also shown to display a dependence on the waveguide width. Optimum laser condition is obtained for waveguide structures with 7.5 μm widths. © 1995.
• Halvorson, C., Kraabel, B., Heeger, A. J., Volodin, B. L., Meerholz, K., & Peyghambarian, N. (1995). Optical computing by use of photorefractive polymers. Optics Letters, 20(1), 76-78.
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  Abstract: Demonstrated is the use of a photorefractive (PR) polymer with very high diffraction efficiency in a matched-filter optical correlator. The device is capable of comparing 5000-pixel test images with a reference image, with a rate limited by only the configuration time of the spatial light modulators (SLMs) and the response time of the detection system. The low cost and the good processability of the PR polymers make them especially attractive for applications.
• Kippelen, B., Meerholz, K., Sandalphon, ., Volodin, B., & Peyghambarian, N. (1995). Nonlinear photorefractive polymers. Optical Materials, 4(2-3), 354-357.
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  Abstract: We discuss the photorefractive properties of polymer composites. Recent developments in the description of the photorefractive effect in these new materials are described and their properties are compared to existing inorganic crystals. High diffraction efficiencies (86%) and high net two-beam coupling gain (200 cm-1) are demonstrated. © 1995.
• Kippelen, B., Meerholz, K., Volodin, B., & Peyghambarian, N. (1995). Recent advances in photorefractive polymer composites. Molecular Crystals and Liquid Crystals Science and Technology Section B: Nonlinear Optics, 11(1-4), 263-275.
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  Abstract: Highly efficient photorefractive polymer composites based on the photoconductor poly(N-vinylcarbazole) and azo dyes as second-order nonlinear optical chromophores, are presented. The photorefractive properties are studied by means of four-wave mixing and two-beam coupling experiments. The photoconducting and electro-optic properties are investigated independently and compared to existing models. The moderate electro-optic properties indicate that other contributions such as birefringence are responsible for the high diffraction efficiencies measured in these samples.
• Kippelen, B., Sandalphon, ., Meerholz, K., & Peyghambarian, N. (1995). Birefringence, Pockels, and Kerr effects in photorefractive polymers. Applied Physics Letters, 1748-.
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  Abstract: A simple frequency-dependent ellipsometric technique for measuring the birefringence, the Pockels and Kerr properties of low glass-transition temperature photorefractive polymers is proposed. The technique is applied to the characterization of highly efficient DMNPAA:PVK:ECZ:TNF photorefractive polymers and the determination of the microscopic properties of the DMNPAA molecule. © 1996 American Institute of Physics.
• Krol, M. F., Leavitt, R. P., Pham, J. T., McGinnis, B. P., & Peyghambarian, N. (1995). Enhanced electroabsorption in selectively doped (Ga,In)As/(Al,In)As asymmetric double quantum wells. Applied Physics Letters, 66(22), 3045-3047.
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  Abstract: A novel electroabsorption mechanism based on selective doping of (Ga,In)As/(Al,In)As asymmetric double quantum wells (ADQWs) was demonstrated. The modulator applied real space transfer of excess electrons to provide effective absorption modulation. The results were compared to absorption changes in an undoped ADQW structures that employed quantum confined stark effect.
• Li, C. -., Chisham, J., Andrews, M., Najafi, S. I., Mackenzie, J. D., & Peyghambarian, N. (1995). Sol-gel integrated optical coupler by ultraviolet light imprinting. Electronics Letters, 31(4), 271-272.
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  Abstract: The authors describe a simple low temperature method for fabricating a low-loss singlemode integrated optical directional coupler in a photosensitive, hybrid, organically modified sol-gel silica glass. The fabrication process is appealing for its simplicity, entailing few steps and using elementary photodefinition to give robust, mechanically rigid devices.
• Li, C. -., Ingenhoff, J., Najafi, S., Chisham, J., MacLachlan, M., Andrews, M. P., Kao, Y., Mackenzie, J. D., Ohtsuki, T., & Peyghambarian, N. (1995). Er-doped sol-gel glasses for integrated optics. Proceedings of SPIE - The International Society for Optical Engineering, 2397, 430-444.
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  Abstract: Erbium-doped glasses are of great interest for optical fiber telecommunications at 1.5 μm. The sol-gel process offers many advantages for synthesizing materials for integrated optical devices. Some of these advantages include high-purity, low- temperature synthesis, and excellent control and flexibility over composition and design. In this paper, we report the first Er- doped sol-gel waveguides. We examined several approaches for alleviating the OH- quenching problem associated with conventional sol-gel processes. We prepared the first ion exchangeable Er-doped glasses which can be fabricated into integrated optical devices. The concept of molecular docking of Er as a coordinate complex in gel matrices to improve the luminescence properties has been applied. We also exploited the concept of using the evanescence field to couple energy into an Er-doped sol-gel layer on top of a glass optical device. New progresses in modifying the properties of gel matrices for integrated optical device applications are presented.
• Meerholz, K., Volodin, B. L., Kippelen, B., & Peyghambarian, N. (1995). High-performance PVK-based photorefractive polymers. Proceedings of SPIE - The International Society for Optical Engineering, 2526, 122-129.
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  Abstract: Photorefractive materials have many potential photonic applications, including dynamic holographic storage and image processing. Recently, the new class of photorefractive polymers has emerged, offering wide structural flexibility, easy processability, and low cost. Progress in this field has led to nearly 100% diffraction efficiency for the readout of a hologram stored in the material and to extremely large net gain coefficients of more than 200 cm-1. These excellent properties result from refractive index modulations as large as Δn ≈ 10-2 which could be generated in these materials with low- power lasers, such as HeNe laser or laser diodes.
• Micic, O. I., Sprague, J. R., Curtis, C. J., Jones, K. M., Machol, J. L., Nozik, A. J., Giessen, H., Fluegel, B., Mohs, G., & Peyghambarian, N. (1995). Synthesis and characterization of InP, GaP, and GaInP₂ quantum dots. Journal of physical chemistry, 99(19), 7754-7759.
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  Abstract: Quantum dots (QDs) of InP, GaP, and GaInP2 with diameters ranging from 20 to 65 A were synthesized as well-crystallized nanoparticles with bulk zinc blende structure. The synthesis of InP, GaP, and GaInP2 QDs was achieved by heating appropriate organometallic precursors with stabilizers in high boiling solvents for several days to produce QDs which can be dissolved in nonpolar organic solvents, forming transparent colloidal QD dispersions. The high sample quality of the InP and GaP QDs results in excitonic features in the absorption spectra. Ternary QDs of GaInP2 were synthesized with a well-crystallized zinc blende structure and lattice spacing between InP and GaP. The QDs were characterized by TEM, powder x-ray diffraction, steady state optical absorption and photoluminescence spectroscopy, transient photoluminescence spectroscopy, and fs to ps pump-probe absorption (i.e., hole-burning) spectroscopy.
• Moerner, W. E., & Peyghambarian, N. (1995). Advances in photorefractive polymers. Optics and Photonics News, 6(3), 24-29.
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  Abstract: This is a review of the recent advances in photorefractive polymers. These advances have made photorefractive polymers worthy of considerations for fundamental reasons as well as for possible technological applications such as optical processing and storage.
• Mohs, G., Fluegel, B., Giessen, H., Tajalli, H., Peyghambarian, N., Chiu, P., Phillips, B., & Osinski, M. (1995). Photoluminescence decay dynamics in an InGaN/AlGaN/GaN double-heterostructure blue-light-emitting diode. Applied Physics Letters, 67(11), 1515-1517.
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  Abstract: Time-resolved investigations of photoluminescence (PL) in an InGaN/AlGaN/GaN double-heterostructure blue-light-emitting diode were carried out. Using an ultrafast laser, the photoluminescence was excited above the bandgap of the layers of interest, then spectrally and temporally measured. By varying the intensity and wavelength of the excitation, as well as studying different parts of the structure, the details of the PL were elucidated. A complicated, two-component behavior of the impurity-related PL was found and is explained by a simple saturable three-level model. Measurements at the band edge indicate stimulated emission as the dominant recombination process for high carrier densities.
• Murray, J. T., Powell, R. C., & Peyghambarian, N. (1995). Properties of stimulated Raman scattering in crystals. Journal of Luminescence, 66-67(1-6), 89-93.
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  Abstract: This paper summarizes our current research on the development of solid-state Raman lasers based on new materials and novel cavity designs. Criteria for selecting good materials for stimulated Raman scattering are reviewed and a theoretical model is presented to demonstrate the origin of Raman beam cleanup.
• Najafi, S., Li, C. -., Andrews, M. P., Chisham, J., Lefebvre, P., Mackenzie, J. D., & Peyghambarian, N. (1995). Integrated optics devices by ultraviolet light imprinting in sol-gel silica glass. Proceedings of SPIE - The International Society for Optical Engineering, 2401, 110-115.
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  Abstract: We describe a simple low temperature method to produce integrated optics devices in a photosensitive, hybrid, organically modified sol-gel silica glass. In particular, we report on fabrication and characterization of slab and channel waveguides, waveguides with grating and a directional coupler. The fabrication process is appealing for its simplicity, entailing few steps and utilizing elementary photodefinition to give robust, mechanically rigid devices.
• Ohtsuki, T., Honkanen, S., Li, C. -., Najafi, S., Powell, R. C., & Peyghambarian, N. (1995). Gain characteristics of a high-concentration Er3+ doped phosphate glass waveguide. Proceedings of SPIE - The International Society for Optical Engineering, 2401, 95-102.
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  Abstract: A channel waveguide on an erbium doped phosphate laser glass (Kigre Q89) was fabricated by a dry silver-film ion exchange technique, and its gain properties were studied experimentally. The propagation loss of the fabricated waveguide was 0.6 dB/cm at 1.3 μm. Er3+ concentration of 1 × 1020 ions/cm3 was chosen so that no concentration quenching occurred. This was confirmed by measuring a fluorescence lifetime of 1.54 μm (8.4 ms). Gain of the fabricated waveguide was measured by using a Ti:sapphire laser at a wavelength of 977 nm and a laser diode of 1.530 μm producing pump and signal beams respectively. The signal wavelength used for the experiments was shorter than the emission peak, and the measured gain of the 1.8 cm waveguide was comparable to the total loss. However, the model which adopted experimental conditions showed that lasing is expected at the emission peak with a 3.6 cm long waveguide fabricated by current method. Calculations results showed that the 6.5 dB gain can be realized at 300 mW pump power with a 5.4 cm long waveguide, provided that mode overlap can be increased by 25% and propagation loss can be reduced by 50%. No significant upconversion effect was observed up to 1.1 × 106 W/cm2 pump intensity.
• Ohtsuki, T., Peyghambarian, N., Honkanen, S., & Najafi, S. I. (1995). Gain characteristics of a high concentration Er³⁺-doped phosphate glass waveguide. Journal of Applied Physics, 78(6), 3617-3621.
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  Abstract: A channel waveguide on an erbium-doped phosphate laser glass was fabricated by a dry silver-film ion exchange technique, and its gain properties were studied experimentally. The propagation loss of the fabricated waveguide was 0.63 dB/cm at 1.3 μm. Er3+ concentration of 1×10 20 ions/cm3 was chosen so that no concentration quenching occurred. This was confirmed by measuring a fluorescence lifetime of 8.4 ms at 1.54 μm. Gain of the fabricated waveguide was measured by using a Ti:sapphire laser at a wavelength of 980 nm and a laser diode of 1.532 μm producing pump and signal beams, respectively. The signal wavelength used for the experiments was shorter than the emission peak, and the measured gain of the 1.8 cm waveguide was comparable to the total loss. However, the model showed that lasing is expected at the emission peak with a 3.6 cm long waveguide fabricated in a similar manner. Calculation results showed that the potential gain of 8.8 dB can be realized with 250 mW pump power, and a 7.2 cm long waveguide provided that mode overlap can be increased by 20% and propagation loss can be reduced by 50%. No significant upconversion effect was observed up to 1.1×10 6 W/cm2 pump intensity. © 1995 American Institute of Physics.
• Peyghambarian, N. (1995). Thanks for the memory. Nature, 378(6555), 339-340.
• Sandalphon, ., Volodin, B. L., Kippelen, B., & Peyghambarian, N. (1995). New photorefractive polymers for optical systems. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 2, 259-.
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  Abstract: We review the physics and performance of recently developed photorefractive polymers that exhibit refractive index modulation amplitudes of 0.007 and net gain coefficients in excess of 200 cm-1. Several examples of applications based on these materials are presented. Future trends in materials and related optical system developments are discussed.
• Volodin, B. L., Meerholz, K., Kippelen, B., Kukhtarev, N. V., & Peyghambarian, N. (1995). Highly efficient photorefractive polymers for dynamic holography. Optical Engineering, 34(8), 2213-2223.
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  Abstract: The performance of recently developed by highly efficient photorefractive polymers based on the photoconducting polymer host poly-(N-vinylcarbazole) is investigated, and the use of these materials as recording media in dynamic holography and other applications is evaluated. A diffraction efficiency η ≈ 86% (limited only by absorption and reflection losses), a two-beam coupling net gain coefficient Γ = 200 cm-1 and light-induced refractive index modulations as high as Δn = 7 × 10-3 are demonstrated. Hologram growth rates of the order of 500 ms are observed with recording light intensities < 10 mW/cm2, using either low-power laser diodes (675 nm) or a HeNe laser (633 nm). The materials show good sensitivity in this part of the spectrum. Applications such as dynamic time-average interferometry are demonstrated.
• Volodin, B. L., Meerholz, K., Sandalphon, S., Kippelen, B., & Peyghambarian, N. (1995). Performance evaluation of a highly efficient photorefractive polymer. Proceedings of SPIE - The International Society for Optical Engineering, 2405, 143-147.
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  Abstract: The performance of photorefractive polymers has improved considerably over the last few years, leading to the recent observation of 86% diffraction efficiency and a net two-beam coupling gain of more than 200 cm-1 in a poly(N-vinylcarbazole)-based polymer doped with the azo dye 2,5-dimethyl-4-(p-nitrophenylazo)anisole. This performance by far surpasses the other organic PR materials reported to date. We report experimental results that evaluate the suitability of this polymer composite for dynamic holography and other applications.
• Woggon, U., Wind, O., Klingshirn, C., Giessen, H., Fluegel, B., Mohs, G., & Peyghambarian, N. (1995). Nonlinear absorption and gain in CdSe and CdSSe quantum dots. Materials Science Forum, 182-184, 93-98.
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  Abstract: Using nanosecond and femtosecond pump-and-probe experiments, we identify the dipole-allowed optical transitions and investigate the temporal development of the nonlinear absorption and gain spectra, their dependence on the size, and the relaxation processes of the excited electron-hole-pair states in CdSe and CdSSe quantum dots.
• Basmaji, P., Surdutovich, G., Vitlina, R., Kolenda, J., Bagnato, V. S., Mohajeri-Moghaddam, H., & Peyghambarian, N. (1994). Anisotropy investigations and photoluminescence properties of porous silicon. Solid State Communications, 91(8), 649-653.
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  Abstract: Porous silicon layers have been investigated using reflectance and photoluminescence techniques at room and liquid nitrogen temperatures. We observe a noticeable anisotropy of porous silicon samples. The measured parallel and normal components of the refractive index for samples with moderate porosity were 1.25 and 1.30, respectively. Possible mechanisms for the origin of the photoluminescence are discussed. © 1994.
• Bescher, E. P., Mackenzie, J. D., Ohtsuki, T., & Peyghambarian, N. (1994). Rare earth/organic dye nanocomposites by the sol-gel method. Materials Research Society Symposium - Proceedings, 351, 135-139.
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  Abstract: This paper describes the processing of rare-earth/organic dye composites fabricated via three different sol-gel routes. In the first approach, low hydroxyl ormosil matrices were fabricated via reaction of a methyl-modified silicon halide with tertiary alcohol and subsequently doped with erbium iodide and a near-infrared dye. In the second approach, gels were made from tetramethoxysilane and doped with erbium complexes and dyes. In the third approach, a hybrid siloxane method was used. No Er3+ luminescence at 1.55 mm was observed in any of the three cases, mainly due to the strong absorption of the matrices centered around 1.4 mm. Fluorescence of Er3+ in the visible was observed in the first matrice, but no dye luminescence was detected. Dye luminescence was observed in the second type matrix, along with some reabsorption of the dye luminescence by Er3+. In the third approach, neodymium exhibited optical activity in the near infrared, as well as the dye.
• Giessen, H., Fluegel, B., Mohs, G., Peyghambarian, N., Sprague, J. R., Micic, O. I., & Nozik, A. J. (1994). Observation of the quantum confined ground state in InP quantum dots at 300 K. Applied Physics Letters, 304-.
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  Abstract: Colloidal suspensions of InP quantum dots (diameters 25 and 35 Å) show steplike absorption spectra which are blue-shifted by about 1 eV with respect to bulk material. Time resolved femtosecond spectroscopy at room temperature identifies the first quantum confined state. The nonlinear bleaching signal rises within 300 fs and persists longer than 200 ps. © 1996 American Institute of Physics. [S0003-6951(96)04503-6].
• Kang, K., Kepner, A. D., Hu, Y. Z., Koch, S. W., Peyghambarian, N., Li, C. -., Takada, T., Kao, Y., & Mackenzie, J. D. (1994). Room temperature spectral hole burning and elimination of photodarkening in sol-gel derived CdS quantum dots. Applied Physics Letters, 64(12), 1487-1489.
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  Abstract: The paper reports on the observed room temperature spectral hole burning in three CdS quantum dot samples with identical particle sizes prepared by the sol-gel process and the conventional glass fusion technique. Room temperature spectral hole burning was utilized as a method to characterize the nonlinearity of the different samples and to understand the origin of the photodarkening effect. It was observed that the difference in the photodarkening mechanism of the three samples is attributed to the different media surrounding the quantum dots. Photodarkening is reduced considerably in the sol-gel samples with high silica content resulting in an approximately 20 times larger nonlinearity compared with the melt-quenched samples. The luminescence efficiency was also observed to be larger in the sol-gel samples.
• Kepner, A. D., Kang, K. I., Hu, Y. Z., Gaponenko, S. V., Koch, S. W., & Peyghambarian, N. (1994). Direct observation of the biexciton ground state in semiconductor quantum dots. Proceedings of the International Quantum Electronics Conference (IQEC'94), 135-136.
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  Abstract: The usual pump-probe experimental approach was modified by adding a third laser beam called the 'saturator' beam. The role of the saturator, with an intensity much larger than that of the pump, was to constantly saturate the lowest-energy exciton transition of the larger dots in the samples. Thus the bleaching of the lowest-energy exciton transition in the larger dots did not hide the induced absorption due to biexciton formation in the smaller dots.
• Kippelen, B., Sandalphon, ., Meerholz, K., Volodin, B., Lyon, S. R., Padias, A. B., Hall Jr., H. K., & Peyghambarian, N. (1994). Photorefractivity and photoisomerization in azo-dye-doped polymers. Materials Research Society Symposium Proceedings, 328, 577-582.
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  Abstract: The photorefractive properties of photoconducting polymers doped with nonlinear azo dyes are investigated by means of polarization and field-dependent four-wave mixing experiments. The nonlocal response of the photorefractive effect is shown by two-beam coupling experiments. High diffraction efficiencies (>5%) and net coupling gain (6 cm-1) are demonstrated at low power with a semiconductor laser diode in 105 μm films. Under some conditions, gratings due to photoisomerization of the azo dye molecules are also present and their properties are discussed.
• Lee, S. G., Kang, K. I., Guerreiro, P., Peyghambarian, N., Najafi, S. I., Zhang, G., Kao, Y. H., Li, C. Y., Takada, T., & Mackenzie, J. (1994). Femtosecond pulse propagation in a cadmium sulfide semiconductor quantum dot waveguide. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting, 8, 85-86.
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  Abstract: Quantum dot waveguides were constructed in order to examine femtosecond pulse propagation behavior in them. Pulse break up were noted in these CdS quantum dot waveguides. The waveguides may be utilized in the manufacture of novel integrated optical devices, for instance lasers and low threshold all-optical switches.
• Meerholz, K., Volodin, B., Kippelen, B., & Peyghambarian, N. (1994). Demonstration of high diffraction efficiency and two-beam-coupling net gain in a photorefractive polymer composite. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting, 8.
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  Abstract: Presented in this paper is a systemic study which includes the dependence of the diffraction efficiency in four-wave-mixing (FWM) experiments on the power density of the writing beams. A significant improvement in diffraction efficiency is obtained.
• Meissner, K., Fluegel, B., Giessen, H., Mohs, G., Binder, R., Koch, S. W., & Peyghambarian, N. (1994). Carrier dephasing in the gain region of an inverted semiconductor. Physical Review B, 50(23), 17647-17650.
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  Abstract: The polarization dephasing time has been measured across the gain region, at the transparency point, and into the absorption region of an optically excited GaAs multiple-quantum-well sample using spectral hole burning and degenerate four-wave mixing techniques. We observe strongly energy-dependent dephasing rates with a minimum at the crossover from gain to absorption. Numerical results for the microscopically calculated carrier-carrier scattering rates for a two-component electron-hole plasma in quantum wells show fair agreement with the experimental findings. © 1994 The American Physical Society.
• Meissner, K., Fluegel, B., Giessen, H., Mohs, G., Binder, R., Koch, S. W., & Peyghambarian, N. (1994). Frequency-dependent dephasing in an inverted semiconductor. Proceedings of the International Quantum Electronics Conference (IQEC'94), 197-.
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  Abstract: Recent theoretical calculations have shown a strong k dependence of the dephasing time across the gain region at the transparency point and in the absorption region of an inverted semiconductor. In the presence of a dense plasma, it is predicted that the dephasing rate approaches zero at the transparency point and increases in both the gain and absorption regions. We have obtained the first complete experimental verification of this phenomenon by using femtosecond-DFWM and spectral-hole-burning measurements in an optically excited semiconductor. In this study we prepared a low-temperature semiconductor in a state of optical gain and then measured the dephasing time at, below, and above the Fermi edge.
• Murray, J. T., Peyghambarian, N., & Powell, R. C. (1994). Near infrared optical parametric oscillators. Optical Materials, 4(1), 55-60.
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  Abstract: Optical parametric oscillators are becoming important sources of tunable coherent radiation in the near infrared spectral region. This paper summarizes some of the basic concepts of infrared optical parametric oscillators and presents the results of calculated performance parameters of devices based on arsenate crystals. © 1994.
• Murray, J. T., Peyghambarian, N., Powell, R. C., Stolzenberger, R. A., Jie, S., & Jassemnejad, B. (1994). Phase-matching techniques and frequency-conversion efficiency in optically active crystals. Physical Review A, 49(5), 4066-4076.
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  Abstract: Many materials of potential interest for nonlinear optical applications exhibit optical activity and this is generally not taken into account in the standard theoretical treatments of nonlinear optical effects. In this paper we examine the conditions under which optical activity significantly alters the nonlinear optical properties of a material and show how this mechanism might be used in designing a nonlinear optical device. First, an algorithm is developed to calculate the exact optimum phase-matching angles and conversion efficiency for three-wave interactions in optically active biaxial crystals. Corrections to the standard theoretical expressions for birefringent phase-matching angles and conversion efficiency are obtained for application to biaxial crystals with large natural birefringence. Second, a generalized quasi-phase-matching scheme based on the presence of optical activity is formulated for three-wave interactions in second-order nonlinear crystals. It is shown that quasi-phase-matching via optical activity can be achieved by way of an effective harmonic modulation of deff, the effective second-order nonlinear coefficient. For both these effects, it is found that optical activity makes a negligible change in the nonlinear optical properties of a material such as KTiOPO4, but they may become important for liquid crystals or polymers with high optical rotation and small birefringence. © 1994 The American Physical Society.
• Peyghambarian, N. (1994). Femtosecond pulse propagation in the gain region of laser amplifiers and applications to subpicosecond switching. IEEE LEOS Annual Meeting - Proceedings, 2, p 75.
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  Abstract: Experiments were performed to investigate the femtosecond laser pulses with high-enough intensity tune inside the gain region of laser amplifiers. Transmission and cross-correlation measurements were performed using 135-fs FWHM pulses propagating through a semiconductor laser diode amplifier prepared with anti-reflection coated facets. A self-modelocked Ti:sapphire laser operating at 90 MHz was tuned across the bandedge of a laser diode with 30 mA of injection current. The laser was tuned to the peak of the gain, and the transmission of the laser diode as a function of input pulse energy was measured. The laser diode initially exhibited gain saturation as the input pulse energy continued to decrease as the pulse underwent induced absorption.
• Kang, K. I., Kepner, A. D., Gaponenko, S. V., Koch, S. W., Hu, Y. Z., & Peyghambarian, N. (1993). Confinement-enhanced biexciton binding energy in semiconductor quantum dots. Physical Review B, 48(20), 15449-15452.
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  Abstract: Experimental observation of the ground-state biexciton transition in CdSxSe1-x quantum dots in glass is presented in a three-beam experiment, involving a probe, a pump, and a saturating laser pulse. The observed quantum-dot biexciton ground state has a strongly enhanced binding energy compared to the bulk as theoretically predicted. The biexciton binding energy is measured as a function of quantum-dot size and the results are compared with calculations. © 1993 The American Physical Society.
• Kippelen, B., Sandalphon, ., Peyghambarian, N., Lyon, S. R., Padias, A. B., & Hall Jr., H. K. (1993). New highly efficient photorefractive polymer composite for optical-storage and image-processing applications. Electronics Letters, 29(21), 1873-1874.
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  Abstract: Reversible holographic storage and beam amplification has been achieved in a new polymer composite using a low-power semiconductor visible laser diode emitting at 674 nm. This material shows substantially better performance than the existing photorefractive polymeric materials. A diffraction efficiency of 5%, a gain coefficient of 30 cm-1 and a net gain of 6 cm-1 have been measured in 105 μm-thick samples with an applied field of 40 V/μm.
• Kippelen, B., Tamura, K., Peyghambarian, N., Padias, A. B., & Hall Jr., H. K. (1993). Photorefractive effect in a poled polymer containing the tricyanovinylcarbazole group. Journal of Applied Physics, 74(5), 3617-3619.
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  Abstract: The photorefractive properties of a poled polymer containing the tricyanovinylcarbazole group with an alkylene spacer are investigated by four-wave mixing experiments and Mach-Zehnder type electro-optic measurements. The photorefractive effect is demonstrated in a polymer that shows both the photoconductivity and the electro-optic effect intrinsically.
• Kippelen, B., Tamura, K., Peyghambarian, N., Padias, A. B., & Hall Jr., H. K. (1993). Photorefractivity in a functional side-chain polymer. Physical Review B, 48(15), 10710-10718.
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  Abstract: An experimental study of the photorefractive effect in a polymeric material containing carbazole and the second-order tricyanovinylcarbazole moieties as a side chain is presented. This polymeric system exhibits intrinsically both photoconductivity and the electro-optic effect. Absorptive and photorefractive gratings have been evidenced by four-wave-mixing experiments and electro-optic measurements. The properties of the photorefractive gratings are studied by investigating the electric-field dependence of the diffraction efficiency. The dynamics of the erase-write behavior of the gratings, as well as permanent photobleaching of the polymer, are described. © 1993 The American Physical Society.
• Meissner, K., Fluegel, B., Giessen, H., McGinnis, B. P., Paul, A., Binder, R., Koch, S. W., Peyghambarian, N., Grün, M., & Klingshirn, C. (1993). Spectral hole burning in the gain region of an inverted semiconductor. Physical Review B, 48(20), 15472-15475.
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  Abstract: We report on the observation and numerical calculations of femtosecond gain dynamics in an optically excited, CdSe epitaxial sample at low temperature. Spectral hole burning is clearly observed around the pump as it is tuned through the gain region. The pump-probe experiments agree well with our theory that involves numerical evaluation of the semiconductor Bloch equations in the presence of carrier-carrier and carrierLO-phonon scattering. © 1993 The American Physical Society.
• Yumoto, J., Lee, S. G., Kippelen, B., Peyghambarian, N., Aitken, B. G., & Borrelli, N. F. (1993). Enhancement of optical nonlinearity of heavy-metal oxide glasses by replacing lead and bismuth with thallium. Applied Physics Letters, 63(19), 2630-2632.
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  Abstract: We report on the results of degenerate four-wave mixing experiments at a wavelength of 1.06 μm on a number of heavy-metal gallate glasses. The replacement of lead (Pb) and/or bismuth (Bi) by thallium (Tl) leads to an enhancement of the optical nonlinearity, resulting in the largest nonresonant electronic nonlinearity yet reported for an oxide glass. χ(3) is proportional to the concentration of Tl; samples with more than 25 cation % Tl have χ(3) larger than that of carbon disulfide (CS2). The optical nonlinearity has an off-resonant electronic origin, which is confirmed by measurements of the diagonal and off-diagonal components of the χ(3) tensor.
• Fluegel, B. D., Paul, A., Meissner, K., Binder, R., Koch, S. W., Peyghambarian, N., Sasaki, F., Mishina, T., & Masumoto, Y. (1992). Experimental and theoretical investigation of femtosecond carrier relaxation in CdSe. Solid State Communications, 83(1), 17-19.
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  Abstract: A femtosecond spectral hole burning technique is employed to study the relaxation of nonequilibrium carriers via carrier-carrier and carrier-LO-phonon scattering. Excitation by 70-fs laser pulses several LO phonon energies above the exciton resonance at 10 K in CdSe results in a transient spectral hole that disappears in less than 100 fs. The experiments are compared with a theory that involves numerical evaluation of the semiconductor Bloch equations in the presence of carrier-carrier and carrier-LO phonon scattering. © 1992.
• Harten, P. A., Lee, S. G., Sokoloff, J. P., Salcedo, J. R., & Peyghambarian, N. (1992). Noise in a dual dye jet hybridly mode-locked near infrared femtosecond laser. Optics Communications, 91(5-6), 465-473.
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  Abstract: The noise properties of a near infrared hybridly mode-locked dye laser system operating in the 100 fs pulse regime are investigated. Two closely spaced cavity length values near the zero mismatch point are identified which produce distinctly different pulses. These pulse trains and the pump laser pulse train are examined in the time and frequency domains for the purpose of determining their usefulness for the study of ultrafast physical processes. The differences in pulse energy fluctuation, pulse width fluctuation, and intensity autocorrelation of the two modes of operation are explained in terms of cavity detuning effects. © 1992.
• Kang, K. I., McGinnis, B. P., Sandalphon, ., Hu, Y. Z., Koch, S. W., Peyghambarian, N., Mysyrowicz, A., Liu, L. C., & Risbud, S. H. (1992). Confinement-induced valence-band mixing in CdS quantum dots observed by two-photon spectroscopy. Physical Review B, 45(7), 3465-3468.
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  Abstract: One- and two-photon absorption spectra of the quantum-confined transitions of CdS quantum dots are reported. The results show significant deviations from calculations based on the parabolic-valence-band approximation. The near-degenerate one- and two-photon transitions observed experimentally, and confirmed theoretically using Luttinger theory and numerical matrix diagonalization, clearly demonstrate the effects of valence-band mixing and Coulomb interaction. © 1992 The American Physical Society.
• Koch, S. W., Hu, Y. Z., Fluegel, B., & Peyghambarian, N. (1992). Coulomb effects and optical properties of semiconductor quantum dots. Journal of Crystal Growth, 117(1-4), 592-597.
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  Abstract: Earlier results of Coulomb effects and optical properties of semiconductor quantum dots are extended to include the confinement induced valence band mixing. The electron-hole-pari energies and wavefunctions are computed combining Luttinger theory with numerical matrix diagonalization techniques. Examples of optical absorption spectra are presented showing significant modification caused by the band mixing. © 1992.
• Masumoto, Y., Fluegel, B., Meissner, K., Koch, S. W., Binder, R., Paul, A., & Peyghambarian, N. (1992). Band-gap renormalization and optical gain formation in highly excited CdSe. Journal of Crystal Growth, 117(1-4), 732-737.
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  Abstract: This paper reports the direct femtosecond observation of the dynamical bandgap renormalization and optical gain formation in a highly excited CdSe crystal. Interband excitation with 60 fs pulses results in broadening of the exciton at 0 fs, exciton bleaching and bandgap renormalization at 80 fs, and development of optical gain below the exciton level after 80 fs with rise time of 100 fs. At 380 fs, the optical gain reaches its maximum value and subsequently decreases slowly. Stimulated plasma luminescence has a peak around the energy where maximum gain is observed. The data are discussed in terms of plasma cooling, screening, state filling, and band-gap renormalization. © 1992.
• Mishina, T., Masumoto, Y., Fluegel, B., Meissner, K., & Peyghambarian, N. (1992). Observation of coherent optical phonons in BiI3. Physical Review B, 46(7), 4229-4232.
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  Abstract: Resonant coherent lattice vibrations in the vicinity of the indirect absorption edge in a BiI3 layered crystal are observed in a femtosecond pump-probe experiment. Coherent optical phonons that are impulsively excited by femtosecond pump pulses modulate the phase of probe pulses, causing oscillation of the probe spectrum in time. This oscillation, which has a period given by the period of the oscillation, continues for more than 100 cycles. We speculate that the coherent phonon-assisted indirect exciton transitions also contribute to the data. © 1992 The American Physical Society.
• Sasaki, F., Mishina, T., Masumoto, Y., Fluegel, B., Meissner, K., & Peyghambarian, N. (1992). Femtosecond optical nonlinearities under resonant excitation of excitons in CdSe. Journal of Crystal Growth, 117(1-4), 768-772.
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  Abstract: Femtosecond pump-and-probe spectroscopy was utilized to study the optical nonlinearities of excitons in CdSe. Under resonant excitation of the A-exciton, a 42 meV energy broadening of the B-exciton structure was observed. This broadening is caused by collisions between the A-exciton and the B-exciton. This is a rather unique observation of the scattering process between different kinds of excitons. Analysis indicates that the A-exciton-B-exciton scattering time is 31 fs. This time is well explained by a simple theory. Under resonant excitation of the B-exciton, a fast recovery of the bleaching was observed at the B-exciton. The recovery time of 0.9 ps is explained as the transformation time of B-excitons into A-excitons emitting LO phonons. The observed time constant agrees with the calculated scattering time based on the Fröhlich interaction within an order of magnitude. © 1992.
• Sasaki, F., Mishina, T., Masumoto, Y., Fluegel, B., Meissner, K., & Peyghambarian, N. (1992). Non-equilibrium distribution of hot carriers in a CdSe thin film. Semiconductor Science and Technology, 7(3 B), B160-B163.
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  Abstract: Femtosecond pump-and-probe spectroscopy was adopted to study the hot carrier distribution in a CdSe thin film. In the experiment, a non-thermalized hot carrier distribution was observed when the pump was turned on. The non-thermalized distribution was observed at the 200 meV broad energy range extending from the pump energy to the low energy side. The low energy tail of the non-thermalized distribution indicates that the carrier-LO phonon scattering competes with the carrier-carrier scattering in the thermalization process. In this sense, this observation is a unique example of the non-thermalized hot carrier distribution in semiconductors. From the ratio of the non-thermalized distribution to the total one, the thermalization time was estimated to be 16-40 fs. In the wake of the thermalization, cooling of photogenerated carriers was observed. With an increase of the excitation density up to 1019 cm-3, the carrier cooling rate was slower. The observed cooling rate was slower than the theoretical calculation, taking account of the screening of the carrier-phonon interaction. This is ascribed to the hot phonon effects of the LO phonon and the TO phonon.
• Tamura, K., Padias, A. B., Hall Jr., H. K., & Peyghambarian, N. (1992). New polymeric material containing the tricyanovinylcarbazole group for photorefractive applications. Applied Physics Letters, 60(15), 1803-1805.
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  Abstract: We report on the synthesis and characterization of a new, completely polymeric material with a large electro-optic coefficient and photoconductivity. A methacrylic ester polymer containing the tricyanovinylcarbazole group with an alkylene spacer was synthesized. With 49 mW laser power, the photoconductivity of the polymer is 9.8×10-10 Ω-1 cm -1 at an applied electric field of 1.4×106 V/cm. Its electro-optic coefficient is 6.1 pm/V. The quantum efficiency of photocarrier generation and the photorefractive figure of merit were calculated. This electro-optic polymer is photoconductive and has photocarrier trap sites without any added sensitizer or photocarrier transport reagent, making it a suitable candidate for photorefractive applications.
• Binder, R., Koch, S. W., Lindberg, M., Peyghambarian, N., & Schäfer, W. (1990). Ultrafast adiabatic following in semiconductors. Physical Review Letters, 65(7), 899-902.
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  Abstract: The full semiconductor Bloch equations are solved to analyze the ultrafast exciton dynamics in semiconductors. Transient adiabatic following is obtained for large detunings and arbitrary intensities, leading to exciton Stark shift, bleaching, and recovery on the time scale of the pump pulse. The many-body Coulomb effects strongly influence the semiconductor response for resonant excitation conditions, almost doubling the effective Rabi frequency of the applied field.
• Binder, R., Lindberg, M., Koch, S. W., & Peyghambarian, N. (1990). Theory of femtosecond transient exciton bleaching and recovery in the optical Stark effect. Proceedings of SPIE - The International Society for Optical Engineering, 1216, 74-80.
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  Abstract: Numerical solutions of the full semiconductor Bloch equations for femtosecond pump-probe excitation are presented. Transient absorption oscillations, optical Stark effect and ultrafast bleaching and recovery of the exciton are reported. A transient population build-up and decay on the time-scale of the pump-pulse is calculated.
• Chuang, C. L., Jin, R., Warren, M., Gibbs, H. M., Sokoloff, J. P., Harten, P. A., Peyghambarian, N., Polky, J. N., & Pubanz, G. A. (1990). Fabrication and performance of GaAs. MQW nonlinear directional coupler. Proceedings of SPIE - The International Society for Optical Engineering, 1216, 13-19.
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  Abstract: Modified fabrication technique has been developed to improve the performance of GaAs/AlGaAs MQW nonlinear directional couplers for all-optical picosecond and subpicosecond switching and modulation. A nonlinear directional coupler (NLDC) capable of switching data streams and demultiplexing signals could be an important component in switching networks. Reliable and reproducible performance depends on the proper technique used to fabricate these devices. Previously, we demonstrated all-optical switching in GaAs/AlGaAs multiple quantum well (MQW) nonlinear directional couplers using 10 ps pulses where the origin of the nonlinearities was due to photo-excited real carriers. The contrast of the ps switching was from 1:3 to 3:1. The contrast of the fs modulation was from 1:2.3 to 1:1.2. Recently, we improved the fabrication procedures. This results in improved performances in both the picosecond and subpicosecond regimes. The MQW waveguide structure was designed to sustain a single planar mode for wavelength close to the absorption edge using a four-layer waveguide model. The effective index method was then used to model the strip-loaded waveguide performance to ensure single mode operation. The sample is grown by molecular beam epitaxy (MBE) and has 1.2 μm thick guiding region which consists of 60 periods of alternating 100 GaAs Wells/100 Al0.28Ga0.72As barriers. The guiding in the direction perpendicular to the MQW is provided by the AlGaAs layers above and below the MQW region whereas the confinement in the horizontal direction is facilitated by the 2 μm wide ridge etched into the top AlGaAs layer.
• Fluegel, B., Joffre, M., Park, S. H., Morgan, R., Hu, Y. Z., Lindberg, M., Koch, S. W., Hulin, D., Migus, A., Antonetti, A., & Peyghambarian, N. (1990). Ultrafast optical nonlinearities in II-VI compounds. Journal of Crystal Growth, 101(1-4), 643-649.
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  Abstract: We review our experimental and theoretical results on the femtosecond laser excited CdS and CdSe bulk and quantum dots. Optical Stark effect in bulk CdS is reported where the electron-hole continuum states in addition to the bound-exciton states are blue shifted. The nonlinear optical properties of CdSe microcrystallites embedded in glass matrices are investigated using femtosecond and nanosecond laser pulses. Spectral hole-buring is observed which is accompanied by an induced absorption feature on the high-energy side. A 25±10 fs dephasing time is obtained from these measurements. It is concluded that Coulomb effects are important in quantum dots. They give rise to a ground state two-pair resonance on the low energy side of the one-pair state and higher energy two-pair resonances which are spectrally located between the one-pair states. Single-beam saturation experiments show that the intensities required for bleaching are larger for smaller crystallites. © 1989.
• Fluegel, B., Koch, S. W., Peyghambarian, N., Hulin, D., Migus, A., Joffre, M., & Antonetti, A. (1990). Femtosecond hole-burning and nonlinear dynamics of quantum confined semiconductor-doped glasses. Proceedings of SPIE - The International Society for Optical Engineering, 1216, 98-104.
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  Abstract: Nonlinear absorption spectra of quantum confined CdSe microcrystallites in glass are measured in a femtosecond pump-probe experiment at low temperatures. Simultaneous bleaching of the transitions, and an induced absorption at higher energy are observed. Spectral hole burning is observed as the pump is tuned through the transition. The system is modelled as spherical crystallites with one or two electron-hole pairs interacting through the Coulomb potential. A numerical matix diagonalization method predicts results essentially similar to the experiment and attributes them to state filling of the one-pair states, and generation of two-pair states.
• Hsu, C. C., Kawabe, Y., Ho, Z. Z., Peyghambarian, N., Polky, J. N., Krug, W., & Miao, E. (1990). Comparison of the χ⁽³⁾ values of crystalline and amorphous thin films of 4-butoxy-carbonyl-methyl-urethane polydiacetylene at 1.06 and 1.3 μm. Journal of Applied Physics, 67(12), 7199-7203.
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  Abstract: The third-order optical nonlinear susceptibilities of single-crystalline and spin-coated amorphous 4-butoxy-carbonyl-methyl-urethane polydiacetylene (red form) thin films were measured by third-harmonic generation. The third-harmonic intensities were calculated as a function of incident angle by solving the propagation equation of the electromagnetic field for a two-layer system with one nonlinear media. From the best fit of the calculated and experimental data, the ( χ(3)) values of the spin-coated amorphous film (χ(3)p) were found to be (9.6±1.0) ×10-12 esu and (2.0±0.2) ×10-11 esu at 1.064 and 1.319 μm, respectively, while the χ(3) values of the crystalline ( χ(3)pc) were (4.9±0.5)×10 -11 esu and (1.0±0.07)×10 -10 esu at 1.064 and 1.319 μm, respectively. A factor of five increase in the χ(3) of the crystalline film is attributed to the orientation effect of the polymer chains. The enhancement of the nonlinearity at 1.319 μm may be due to either three-photon or two-photon resonant effects.
• Hu, Y. Z., Koch, S. W., Lindberg, M., Peyghambarian, N., Pollock, E. L., & Abraham, F. F. (1990). Biexcitons in semiconductor quantum dots. Physical Review Letters, 64(15), 1805-1807.
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  Abstract: Theoretical and experimental results are reported which provide the first evidence for biexciton states in semiconductor quantum dots. The theory predicts an increasing biexciton binding energy with decreasing dot size. Unlike bulk semiconductors, quantum dots have excited biexciton states which are stable. These biexciton states are observed as pronounced induced absorption features on the high-energy side of the bleached exciton resonances in femtosecond and nanosecond pump-probe experiments of quantum dots in glass matrices.
• Hu, Y. Z., Lindberg, M., Koch, S. W., & Peyghambarian, N. (1990). Coulomb effects in optically excited semiconductor quantum dots. Proceedings of SPIE - The International Society for Optical Engineering, 1216, 88-97.
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  Abstract: The linear and nonlinear optical properties of semiconductor microcrystallites are analyzed taking into account the Coulomb interaction between the carriers and the influence of surface charges. A numerical matrix diagonalization method is used to evaluate the energy eigenvalues and the corresponding eigenstates. It is predicted that excited two-pair states lead to a pronounced induced absorption on the high energy side of the one-pair resonance. This prediction is confirmed by femtosecond and nanosecond experiments in CdSe and CdS quantum dots. Additionally, effects of traps or impurities and external dc electric fields are discussed.
• Hulin, D., Joffre, M., Migus, A., Antonetti, A., Peyghambarian, N., Fluegel, B., & Koch, S. W. (1990). Ultrafast optical nonlinearities of CdSe quantum dots. XVII International Conference on Quantum Electronics. Digest of, 178-179.
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  Abstract: Femtosecond differential absorption measurements have been performed on the quantum-confined transitions in CdSe microcrystallites. Spectral hole burning accompanied by increased absorption on the high-energy side is observed. The spectral positions of the induced features depend on the excitation wavelength. For excitation on the low-energy side of the lowest quantum confined transition, a shift of the burned hole with respect to the pump frequency is observed. It is explained in the framework of an inhomogeneous absorption line composed of broad homogeneous lines. A 25 ± 10-fs dephasing time is obtained from the measurements. The results are explained by bleaching of one-pair states and induced absorption caused by the photoexcited two-electron-hole-pair states. It is concluded that Coulomb effects are important even in quantum dots. They give rise to a ground state two-pair resonance on the low-energy side of the one-pair state and to higher-energy two-pair resonances which are spectrally located between the one-pair states.
• Jin, R., Sokoloff, J. P., Harten, P. A., Chuang, C. L., Lee, S. G., Warren, M., Gibbs, H. M., Peyghambarian, N., Polky, J. N., & Pubanz, G. A. (1990). Ultrafast modulation with subpicosecond recovery time in a GaAs/AlGaAs nonlinear directional coupler. Applied Physics Letters, 56(11), 993-995.
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  Abstract: All-optical modulation is observed at room temperature in a GaAs/AlGaAs multiple quantum well nonlinear directional coupler using femtosecond pulses. The origin of the ultrafast (
• Koch, S. W., Hu, Y. Z., Lindberg, M., & Peyghambarian, N. (1990). Coulomb effects in semiconductor quantum dots. XVII International Conference on Quantum Electronics. Digest of, 34-.
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  Abstract: A theoretical analysis of the linear and third-order nonlinear optical properties that includes the one- and two-electron-hole-pair (EHP) states was carried out numerically. The results consistently show that Coulomb effects are important even for the smallest quantum dots. The binding energy of the energetically lowest two-EHP state (loosely referred to as a biexciton), which is a measure of the strength of the Coulomb interaction, is found to increase with decreasing dot radius. It is predicted that energetically higher two-pair states in quantum dots should be quite easily observable as increasing probe absorption on the high-energy side of the one-EHP resonances. Calculations were performed for intrinsic semiconductor quantum dots as well as for quantum dots with trapped charges or impurities. All the investigations show that the predicted features are quite universal and even enhanced in systems with charged impurities or traps. Experiments on quantum dots in a glass matrix clearly show the predicted induced absorption in addition to the bleaching of the inhomogeneously broadened one-EHP resonances.
• Morgan, R. A., Park, S., Koch, S. W., & Peyghambarian, N. (1990). Experimental studies of the non-linear optical properties of cadmium selenide quantum-confined microcrystallites. Semiconductor Science and Technology, 5(6), 544-548.
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  Abstract: The non-linear optical properties of CdSe microcrystallites exhibiting three-dimensional quantum confinement effects are investigated using (i) nanosecond pump-probe spectroscopic techniques and (ii) single beam saturation experiments to study the dependence on particle size. The experimental data show unique non-linear behaviour arising from state filling and Coulomb effects as well as trap-related phenomena exceedingly different from other non-linear optical materials.
• Peyghambarian, N., Koch, S. W., & Seraphin, B. O. (1990). Dynamic Stark effect in semiconductors. High-speed modulation. Proceedings of SPIE - The International Society for Optical Engineering, 1286, 376-380.
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  Abstract: Laser excitation above the bandgap of semiconductor materials like GaAs creates a high density of electrons and holes. These quasi particles form a quantum mechanical system in which optical nonlinearities arise as a result of many-body effects such as screening of the Coulomb potential, reduction of the bandgap, and filling of the band and of the states. The refractive index change resulting from such processes may be employed to demonstrate a variety of devices such as nonlinear switches, modulators, and logic gates. These optical nonlinearities may be measured using various techniques such as four-wave mixing, interferometry, and modulation spectroscopy. In the latter technique, an analogy is established to the electroreflectance effect, in which the optical properties of a semiconductor are modulated by the application of a low-frequency electric field. In the experiment reported, the modulating element is the E-field of the pump beam. At a much higher frequency than in electroreflectance spectroscopy, the pump beam thus produces field-induced reflectance and transmittance changes from which the refractive index change is obtained. Optical Stark effect may be observed in semiconductors as the blue shift of the exciton resonance. At higher pump intensities and smaller pump detunings from the exciton, the real carrier generation, either by one- or two-photon absorption, also affects the observed spectra.
• Sokoloff, J. P., Lee, S. G., Jin, R., Harten, P. A., Binder, R., Koch, S. W., Gibbs, H. M., & Peygham-Barian, N. (1990). Femtosecond recovery of exciton bleaching in the optical Stark effect. XVII International Conference on Quantum Electronics. Digest of, 92-93.
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  Abstract: The observation of a very fast recovery of the exciton bleaching for an off-resonance excitation condition in a quantum-well sample at room temperature is reported. The experiments were performed on a GaAs/AlGaAs multiple quantum well (MQW) with 76-angstrom well sizes. A hybridly mode-locked dye laser that yielded 70-fs (FWHM) pulses at an 82-MHz repetition rate centered at ≅865 nm was used. The time delay was varied by changing the optical path of the pump pulse. The absorption spectra of the probe and the numerically evaluated excitonic absorption spectra, both at various time delays, are shown and discussed. The good agreement between the experimental results and the numerical calculations of the time-resolved absorption spectra suggests a coherent transient population buildup and decay occurring on the time scale of the pump pulse.
• Williams, V. S., Ho, Z. Z., Peyghambarian, N., Gibbons, W. M., Grasso, R. P., O'Brien, M., Shannon, P. J., & Sun, S. T. (1990). Picosecond all-optical logic gate in a nonlinear organic étalon. Applied Physics Letters, 57(23), 2399-2401.
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  Abstract: An all-optical logic gate has been demonstrated in a nonlinear organic étalon using femtosecond laser pulses. The logic gate consists of a guest-host organic thin film, 7-[4-[(4-hexyloxyphenyl)azo](naphthyl)azo-(2,3- dihydro-1,3-dimethyl-2-octyl)] perimidine doped in poly(methyl methacrylate), sandwiched between two highly reflective mirrors. It shows a subpicosecond switch-on time and a switch-off or recovery time that has a fast, ≅4 ps component and slower components. A maximum contrast ratio of ≅2 between the switch-on and switch-off states of the optical gate was obtained. The nonlinear index of refraction is also measured from this Fabry-Perot interferometer to be Δn=0.005.
• Chavez-Pirson, A., Park, S. H., Pereira, M., Peyghambarian, N., Lehman, J. A., Ruden, P. P., & Hibbs-Brenner, M. (1989). Measurement of intensity-dependent carrier lifetime in doping superlattices. CONFERENCE ON LASERS AND ELECTRO-0PTICS, 284-285.
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  Abstract: A structure grown by metalorganic chemical vapor deposition (MOCVD), consisting of ten periods of alternating layers of n- and p-doped GaAs 130-nm thick with a doping concentration of 2 × 1017, was studied. The nonlinear transmission spectrum as a function of intensity as well as the intensity-dependent carrier buildup and decay lifetimes were measured directly using a pump-probe technique. The differential transmission spectrum (ΔT/T) at various pump intensities and the buildup time required to obtain the maximum modulation for a given intensity are shown and discussed. The intensity-dependent decay dynamics was measured by delaying the probe relative to the falling edge of the pump pulse. On a log-log scale the decay of the maximum modulation is linear, indicating a decay time that increases exponentially with decreasing carrier density. Both the buildup and decay dynamics can be effectively modeled with a rate equation whose carrier decay time depends exponentially on carrier density.
• Jin, R., Chuang, C. L., Gibbs, H. M., Warren, M., Sokoloff, J., Harten, P., Peyghambarian, N., Polky, J. N., & Pubanz, G. A. (1989). Polarization-dependent two-beam switching in GaAs/AlGaAs nonlinear directional couplers. CONFERENCE ON LASERS AND ELECTRO-0PTICS, 12-13.
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  Abstract: All-optical modulation and switching have been demonstrated in various nonlinear directional couplers (NLDCs). These experiments were performed by varying the intensity of a single input light beam to change the relative transmission of the two channels. This single-beam method has some undesirable features: the total absolute output of the NLDC in the bar state is much higher than in the cross state, and the large detuning from the band edge needed for high transmission results in a decrease in nonlinearity. The authors propose and demonstrate a technique that uses the output of a single laser, allows a GaAs/AlGaAs NLDC to be operated at a wavelength where its transmission is reasonably high, and still maintains efficient switching. This technique is based on the anisotropic optical properties of quantum-well (QW) structures.
• Peyghambarian, N. (1989). Ultrafast optical nonlinearities of II-VI semiconductor quantum dots. Array, 150, 152.
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  Abstract: CdS and CdSe microcrystallites embedded in silicate glasses are interesting materials for studying 3-D quantum confinement effects. A comprehensive study of optical nonlinearities of a number of CdSe quantum dot samples, using nanosecond and femtosecond laser techniques, is reported. The homogeneous and inhomogeneous contributions to the lowest electronic transitions have been measured using hole-burning. Analysis of the hole width, which increases with increasing light intensity, gives the polarization decay time. Femtosecond four-wave mixing measurements have been performed to obtain the energy relaxation time. The excited state dynamics and optical nonlinearities as a function of microcrystallite size have been investigated.
• Peyghambarian, N., Fluegel, B., Hulin, D., Migus, A., Joffre, M., Antonetti, A., Koch, S. W., & Lindberg, M. (1989). Femtosecond optical nonlinearities of CdSe quantum dots. IEEE Journal of Quantum Electronics, 25(12), 2516-2522.
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  Abstract: Femtosecond differential absorption measurements of the quantum-confined transitions in CdSe microcrystallites are reported. Spectral hole burning is observed, which is accompanied by an induced absorption feature on the high-energy side. The spectral position of the burned hole depends on the excitation wavelength. For excitation on the low-energy side of the lowest quantum-confined transition, a slight shift of the hole towards the line center is observed. The hole width increases with pump intensity and the magnitude of the induced transparency saturates at the highest excitation level. The results are consistently explained by bleaching of one-pair states and induced absorption caused by the photoexcited two electron-hole pair states. It is concluded that the presence of one electron in the excited state prevents further absorption of photons at the pair-transition energy and accounts for the major portion of the bleaching of the transition.
• Peyghambarian, N., Koch, S. W., Lindberg, M., Fluegel, B., & Joffre, M. (1989). Dynamic stark effect of exciton and continuum states in CdS. Physical Review Letters, 62(10), 1185-1188.
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  Abstract: The first observation of the optical Stark effect of electron-hole continuum states in addition to the bound-exciton states is reported under femtosecond excitation conditions chosen to minimize the generation of real carriers. The experimental results agree well with calculations using the generalized semiconductor Bloch equations. The theory shows that the commonly used adiabatic approximation is correct only for pulses which are longer than the coherence decay time. For shorter pulses coherent dynamic effects strongly influence the spectral changes. © 1989 The American Physical Society.
• Stolzenberger, R. A., Hsu, C. C., Peyghambarian, N., Reid, J. J., & Morgan, R. A. (1989). Type II sum frequency generation in flux and hydrothermally grown KTP at 1.319 and 1.338 μm. IEEE Photonics Technology Letters, 1(12), 446-448.
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  Abstract: Type-II, noncritically phase-matched, sum-frequency generation by mixing of the 1.319- and 1.338-μm lines of a Q-switched Nd:YAG laser with their second harmonics is discussed. Results are presented for KTP crystals grown by both the hydrothermal and the flux technique. A temperature-acceptance width-length product of 8.5 ± 0.5°C-cm was determined. Type-II critical phase matching at room temperature, for three different propagation/polarization orientations, is also demonstrated. The differences in the angles required for phase matching between crystals grown by the different techniques are quantified.
• Fluegel, B. D., Sokoloff, J. P., Jarka, F., Koch, S. W., Lindberg, M., Peyghambarian, N., Joffre, M., Hulin, D., Migus, A., Antonetti, A., Ell, C., Banyai, L., & Haug, H. (1988). Measurements of ultrafast optical nonlinearities in semiconductors: Kinetics and transients. Physica Status Solidi (B) Basic Research, 150(2), 357-363.
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  Abstract: The response of a bulk platelet under the influence of nonresonant pulse excitation below the band gap is measured using femtosecond laser techniques. These optical Stark effect measurements are analyzed using the effective Bloch equations for semiconductors. These equations are solved (i) dynamically in the large detuning, low intensity limit and (ii) for arbitrary intensities in the adiabatic limit.
• Ho, Z. Z., & Peyghambarian, N. (1988). Femtosecond dynamics in organic thin films of fluoro-aluminium phthalocyanine. Chemical Physics Letters, 148(2-3), 107-111.
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  Abstract: Femtosecond laser pulses are employed to study the dynamics of the absorption spectra of fluoro-aluminium phthalocyanine polycrystalline thin films. Following excitation by 620 nm pulses into the first electronic transition a very rapid energy relaxation of the excitons is observed within the 55 fs duration of the pump pulse. Following this process two extremely fast decay routes lead to the recovery of the ground state: exciton-exciton annihilation with an intensity-dependent decay of 550 fs at power density of 1.2 GW/cm2 and exciton-phonon coupling with a 4 ps decay time. © 1988.
• Ho, Z. Z., Fluegel, B., Williams, V., & Peyghambarian, N. (1988). Femtosecond dynamics in thin organic films of fluoroaluminum phthalocyanine.. Array, 420, 421.
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  Abstract: Fluoroaluminum phthalocyanine (AlPc-F), which contains a 2-D π-electron system, has shown a relatively large optical nonlinearity [X(3) = 5 × 10-11 esu] and very high laser damage threshold (>20 GW/cm2). The measurement of the electronic dynamics of polycrystalline AlPc-F at room temperature is reported. Femtosecond laser pulses of 150-fs duration at an 8.5-kHz repetition rate are used in this experiment. The more energetic narrowband pump pulse centered at 6200 angstrom creates an excited-state population. The differential transmission spectrum (DTS) of the weaker broadband probe beam is then monitored at the electronic band edge between 7400 and 8600 angstrom. The DTS of the probe pulse at various time delays between the pump and probe pulses, the evolution of the DTS signal at longer time delays up to 15 ps, and the decay of the DTS signal as a function of time for different pumping intensities with the probe at 7800 angstrom of the DTS peak are shown and discussed. An interpretation based on Frenkel exciton terminology successfully accounts for the observed results.
• Koch, S. W., Peyghambarian, N., & Gibbs, H. M. (1988). Band-edge nonlinearities in direct-gap semiconductors and their application to optical bistability and optical computing. Journal of Applied Physics, 63(2), R1-R12.
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  Abstract: Nonlinear optical properties of laser-excited semiconductors are discussed, and the applications to optical bistability and optical logic are reviewed. The physical origin of the nonlinearities is analyzed in terms of the many-body interactions in the system of electron-hole pairs, causing effects such as plasma screening of the Coulomb interaction, band-gap renormalization, and band filling. Theoretical results for absorption and refractive-index spectra are compared to experimental data obtained for room-temperature GaAs and other semiconductors. The experimental and theoretical results for dispersive optical bistability in semiconductors are summarized, and recent experiments on optical logic gating and pattern recognition are discussed.
• Koch, S. W., Peyghambarian, N., & Lindberg, M. (1988). Transient and steady-state optical nonlinearities in semiconductors. Journal of Physics C: Solid State Physics, 21(30), 5229-5249.
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  Abstract: Theory and experiments on steady-state and femtosecond time-resolved optical nonlinearities in semiconductors are reviewed. A simple description of the physical processes underlying the nonlinearities is given. The discussion is focused on the spectral region around the fundamental absorption edge, and it covers coherent oscillations, the optical Stark effect as well as the bleaching of the exciton resonance with increasing excitation intensity, plasma screening and band-filling phenomena. © 1988 IOP Publishing Ltd.
• Morgan, R. A., Hopf, F. A., & Peyghambarian, N. (1988). Three-wave mixing uses of a novel dual-frequency Nd:YAG laser.. Array, 292, 293.
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  Abstract: An experimental technique for generating the 1.318- and 1.064-μm Nd:YAG lines simultaneously is described. The system is used for studying three-wave mixing (3WM) in three commercially available nonlinear crystals. Emission of both 1.064 and 1.318 μm from this single laser makes it possible to generate simultaneously a number of sum frequencies in addition to laser harmonics. The visible frequencies include 0.659, 0.589, 0.532, 0.44 and 0.407 μm.
• Morgan, R. A., Kang, K. I., Hsu, C. C., & Peyghambarian, N. (1988). Novel interferometric technique for measuring thermal diffusivity of nonlinear anisotropic crystals.. Array, 68, 69, 70.
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  Abstract: It has been demonstrated that an all-optical interferometer can be used to measure directly the thermal diffusivity of nonlinear materials by measuring optical path differences only. A lithium niobate crystal was inserted into an interferometer and heated by its absorption of an input pulse from a focused CO2 laser. As the heat diffuses outward in the crystal, the refractive index increases and the crystal expands. The resulting optical path change can be monitored interferometrically in real time, and from fringe data the thermal diffusivity is determined. A Gaussian model for the temperature distribution was derived and verified empirically. The method is quite general and should work for a variety of materials given the proper laser probe and (heat) pump wavelengths. It avoids the need to measure temperature distributions, powers, and critical crystal parameters, dimensions, and angles.
• Park, S. H., Fluegel, B., Morgan, R. A., Koch, S. W., Sokolof, J., Peyghambarian, N., Joffre, M., Potts, J. E., & Cheng, H. (1988). Picosecond recovery of excitonic optical nonlinearities of MBE-grown ZnSe thin films.. Array, 160, 162, 163.
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  Abstract: The observation of large nonlinearity of electronic origin and the measurement of the very fast response time of this nonlinearity are reported. The magnitude and dynamics of this excitonic effect were measured at various temperatures in high-purity ZnSe thin film grown by molecular beam epitaxy on GaAs substrates. Two series of experiments were performed. In the first, a 3-ns laser system was used to measure the nonlinear index of refraction as a function of wavelength at 150 and 300 K. Clear excitonic effects were observed. The experimental results agree well with a partly phenomenological plasma theory that takes into account many-body effects. In the second series of experiments, the response time of the excitonic nonlinearity was measured using femtosecond laser techniques. A very rapid response time for the nonlinearity (exciton recovery time) in the range of 100 ps was measured. The exciton recovery time was faster for thinner samples.
• Park, S. H., Morhange, J. F., Jeffery, A. D., Morgan, R. A., Chavez-Pirson, A., Gibbs, H. M., Koch, S. W., Peyghambarian, N., Derstine, M., Gossard, A. C., English, J. H., & Weigmann, W. (1988). Measurements of room-temperature band-gap-resonant optical nonlinearities of GaAs/AlGaAs multiple quantum wells and bulk GaAs. Applied Physics Letters, 52(15), 1201-1203.
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  Abstract: We present a systematic study of the dependence of the optical nonlinearities on quantum well thickness for GaAs/AlGaAs multiple quantum wells (MQW's) at room temperature and compare them with bulk GaAs. The maximum change in the refractive index is greatest for the MQW's with the smallest well size and decreases with increasing well size, reaching a minimum for bulk GaAs. The maximum index change per photoexcited carrier increases by a factor of 3 as the well size decreases from bulk to 76 Å MQW.
• Peyghambarian, N., Park, S. H., Koch, S. W., Jeffery, A., Potts, J. E., & Cheng, H. (1988). Room-temperature excitonic optical nonlinearities of molecular beam epitaxially grown ZnSe thin films. Applied Physics Letters, 52(3), 182-184.
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  Abstract: Large optical nonlinearities have been observed in molecular beam epitaxially grown thin films of ZnSe at room temperature and at T=150 K. A comparison with a plasma theory indicates that in both cases exciton screening is the dominating mechanism for the nonlinearity. The maximum nonlinear index per excited electron-hole pair at room temperature is comparable to that of bulk GaAs and GaAs-AlGaAs multiple quantum wells. The measured absorption and nonlinear index spectra agree quite well with our calculated values.
• Sokoloff, J. P., Joffre, M., Fluegel, B., Hulin, D., Lindberg, M., Koch, S. W., Migus, A., Antonetti, A., & Peyghambarian, N. (1988). Transient oscillations in the vicinity of excitons and in the band of semiconductors. Physical Review B, 38(11), 7615-7621.
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  Abstract: Several semiconductor materials, including CdS, CdSe, GaAs, and GaAs-AlxGa1-xAs multiple quantum wells were studied with use of femtosecond pump-probe spectroscopy. Oscillatory structures are observed in the differential transmission spectra of the probe pulse at the very early times when the probe pulse precedes the pump pulse. In addition to oscillations around the exciton frequency when pumping is either above or below the exciton, oscillatory structures are also observed in the vicinity of the pump frequency when the pump is tuned inside the semiconductor band. A semiclassical theory qualitatively explains the observed data. These oscillations are found to be the precursors of spectral hole burning (oscillations around the pump for pumping into the band), exciton bleaching (oscillations around exciton for pumping into the band) and exciton optical Stark shift (oscillations around exciton for pumping below the band). © 1988 The American Physical Society.
• Williams, V. S., Olbright, G. R., Fluegel, B. D., Koch, S. W., & Peyghambarian, N. (1988). Optical nonlinearities and ultrafast carrier dynamics in semiconductor doped glasses. Journal of Modern Optics, 35(12), 1979-1993.
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  Abstract: The linear and nonlinear optical properties of commercially available CDSxSe1-x doped glasses are reviewed and the origin, magnitude, and temporal response of the nonlinearities are discussed. The room-temperature carrier dynamics are analyzed using femtosecond interband pump-probe measurements. Our experimental results show the evolution of the carriers into a hot, quasi-thermal plasma distribution via electron-electron and electron-phonon scattering. The quasi-thermal distribution cools to the lattice temperature in about 750 fs filling the states just above the band-edge. This band-filling nonlinearity is seen as the bleaching of the absorption above the band-edge. The carrier recombination lifetime is measured to be ≅ 10 ps at higher carrier densities.
• Bowden, C., Dagenais, M., Garmire, E. M., Leonberger, F. J., Peyghambarian, N. G., Stegeman, G. I., & Wolff, P. A. (1987). Bulk semiconductors. Applied Optics, 26(2), 213-216.
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  PMID: 20454112;Abstract: The range of applications for which the nonlinear optical properties of bulk semiconductors are of interest, is studied. One of the primary reasons for considering bulk semiconductors for nonlinear optics is that they combine an attractive figure of merit with materials and fabrication technologies. This provides substantial leverage in achieving rapid progress in forming structures for important device demonstrations. Semiconductors are also ideal candidates to study the physics of nonlinearities. Glasses doped with microcrystallites of semiconductors are new materials for nonlinear optics. The small crystallite size leads to a very rapid carrier decay time and promise of devices with picosecond switching speeds. A new type of optical bistable device with optical feedback, that uses an electrical input only to create population inversion and gain, has recently been demonstrated. With regard to excitonic nonlinearities, future research should seek semiconductors having sharper room temperature resonances and faster carrier recombination times.
• Fluegel, B., Peyghambarian, N., Olbright, G., Lindberg, M., Koch, S. W., Joffre, M., Hulin, D., Migus, A., & Antonetti, A. (1987). Femtosecond studies of coherent transients in semiconductors. Physical Review Letters, 59(22), 2588-2591.
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  Abstract: The coherent interaction of femtosecond laser pulses and thin CdSe and GaAs samples is investigated experimentally and theoretically. Oscillatory structures in the differential probe transmission around the exciton resonance and around the pump frequency are observed when the probe pulse precedes the pump. Comparison with theory attributes the oscillations to the coherent coupling between the light field and the electron-hole transitions in the semiconductor. For nonresonant excitation, the oscillatory structures around the exciton are identified as the early stages of the optical Stark effect. © 1987 The American Physical Society.
• Gibbs, H. M., & Peyghambarian, N. (1987). NONLINEAR ETALONS AND OPTICAL COMPUTING.. Proceedings of SPIE - The International Society for Optical Engineering, 634, 142-148.
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  Abstract: Nonlinear optics can contribute decisions to optical signal processing and computing. Etalons permit massive parallelism and global interconnectivity. GaAs etalons appear more attractive for real systems, but ZnS interference filters are convenient for simple demonstrations of logic operations and pattern recognition.
• Gibbs, H. M., Peyghambarian, N., Lee, Y. H., Jewell, J. L., Migus, A., Antonetti, A., Hulin, D., & Mysyrowicz, A. (1987). HIGH-SPEED OPTICAL LOGIC USING GaAs.. Array, 25-27.
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  Abstract: The status of bulk-GaAs etalons and their application to high-speed optical logic is summarized. A nonlinear etalon is described that can make a decision in about 1 ps and recover to make another in less than 100 ps, making possible high-speed optical logic. These recovery times are considered to be adequate for parallel computations where thermal considerations will limit the product of pixel density and repetition rate.
• Gibbs, H. M., Peyghambarian, N., Lee, Y. H., Warren, M., Chavez-Pirson, A., Park, S. H., Morhange, J., Jeffrey, A., Koch, S., Gossard, A. C., & Wiegmann, W. (1987). ROOM-TEMPERATURE BULK GaAs: DOMINANT NONLINEARITIES, FAST-RECOVERY GATES, ARRAYS FOR PARALLEL PROCESSING.. Array, 195-205.
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  Abstract: Reduction of continuum enhancement and band filling are the dominant optical nonlinearities at room temperature. Surface recombination gives a 30-ps recovery time following AND-gate operation. Reactive ion etching can be used to define large arrays of pixels for parallel processing.
• Morgan, R. A., Hopf, F. A., & Peyghambarian, N. (1987). DUAL-FREQUENCY Nd:YAG LASER FOR THE STUDY AND APPLICATION OF NONLINEAR OPTICAL CRYSTALS.. Optical Engineering, 26(12), 1240-1244.
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  Abstract: We have devised and demonstrated a technique that allows the simultaneous (in space and time) generation of two independent and well-separated Nd:YAG laser lines. We use this system to study three-wave mixing in nonlinear optical crystals. Application of this laser system coupled with suitable nonlinear optical crystals permitted us to simultaneously generate frequencies extending throughout the visible (including the three primary colors) and into the near-UV.
• Mysyrowicz, A., Hulin, D., Migus, A., Antonetti, A., Gibbs, H. M., Peyghambarian, N., & Morkoc, H. (1987). HIGH-SPEED PHENOMENA IN GaAs MULTIPLE-QUANTUM-WELLS.. Array, 156-158.
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  Abstract: The authors discuss the different optical phenomena occurring within a few picoseconds after irradiation of GaAs multiple-quantum-well structures with femtosecond laser pulses. They mention collision broadening in quantum wells, a shift of the exciton response to higher energy, exciton bleaching, and an optical Stark effect.
• Ojima, M., Chavez-Pirson, A., Lee, Y. H., Morhange, J. F., Juang, F., Bhattacharya, P. K., Weinberger, D. A., Gibbs, H. M., & Peyghambarian, N. (1987). OPTICAL NOR GATE USING DIODE LASER SOURCES.. Array, 229-232.
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  Abstract: Optical logic elements, especially in the form of 2-D arrays, can possibly be applied to massively parallel signal processing. GaAs/AlGaAs multiple-quantum-well etalons have previously shown optical bistability and various types of logic-gate operation at room temperature. Most of these experiments have used a dye laser, which is large in size and expensive. One attractive feature of these devices is that a GaAs/AlGaAs diode laser can be used as a light source making the total system more practical. The paper demonstrates a stable optical NOR gate using two diode lasers.
• Peyghambarian, N. (1987). RECENT ADVANCES IN OPTICAL BISTABILITY.. Fiber and Integrated Optics, 6(2), 117-123.
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  Abstract: Advances in optical bistability and gating of semiconductors are reviewed. Nonlinear mechanisms responsible for switching are described. The advantages of nonlinear etalons for massive parallelism and current problems in performing such operations are discussed.
• Tsao, M. T., Wang, L., Jin, R., Sprague, R. W., Gigioli, G., Kulcke, H. -., Li, Y. D., Chou, H. M., Gibbs, H. M., & Peyghambarian, N. (1987). SYMBOLIC SUBSTITUTION USING ZnS INTERFERENCE FILTERS.. Optical Engineering, 26(1), 41-44.
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  Abstract: Pattern recognition is demonstrated using two-dimensional nonlinear optical logic gate arrays on ZnS and ZnSe interference filters defined by fly's eye lens arrays. Fan-out is demonstrated, allowing symbol scription using these arrays.
• Hulin, D., Mysyrowicz, A., Antonetti, A., Migus, A., Masselink, W. T., Morkoç, H., Gibbs, H. M., & Peyghambarian, N. (1986). Ultrafast all-optical gate with subpicosecond on and off response time. Applied Physics Letters, 49(13), 749-751.
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  Abstract: An all-optical logic gate consisting of a GaAs-GaAlAs multiple quantum well structure inserted in a 1.3-μm-thick Fabry-Perot cavity is demonstrated to perform with subpicosecond on and off switching time. The use of a purely optical field effect allows for a recovery time as rapid as the switch-on time.
• Hulin, D., Mysyrowicz, A., Antonetti, A., Migus, A., Masselink, W. T., Morkoç, H., Gibbs, H. M., & Peyghambarian, N. (1986). Well-size dependence of exciton blue shift in GaAs multiple-quantum-well structures. Physical Review B, 33(6), 4389-4391.
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  Abstract: We have studied the high-energy shift of excitons, observed in GaAs multiple-quantum-well structures at high exciton densities, as a function of well and barrier thickness. The magnitude of the blue shift was found to depend predominantly upon the GaAs layer thickness, increasing at smaller well sizes. This effect is discussed in terms of a quenching of long-ranged many-body Coulomb effects. © 1986 The American Physical Society.
• Lee, Y. H., Chavez-Pirson, A., Koch, S. W., Gibbs, H. M., Park, S. H., Morhange, J., Jeffery, A., Peyghambarian, N., Banyai, L., Gossard, A. C., & Wiegmann, W. (1986). Room-temperature optical nonlinearities in GaAs. Physical Review Letters, 57(19), 2446-2449.
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  Abstract: We report the first systematic study of the frequency dependence of optical nonlinearities of bulk GaAs at room temperature. In contrast to the previous understanding, band filling and plasma screening of Coulomb enhancement of continuum states are found to be the dominant contributions to the dispersive optical nonlinearities under quasi steady-state excitations. The partly phenomenological semiconductor plasma theory is in good agreement with the experimental data. © 1986 The American Physical Society.
• Lee, Y. H., Warren, M., Olbright, G. R., Gibbs, H. M., Peyghambarian, N., Venkatesan, T., Smith, J. S., & Yariv, A. (1986). Streak-camera observation of 200-ps recovery of an optical gate in a windowless GaAs étalon array. Applied Physics Letters Applied Physics Letters, 48(12), 754-756.
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  Abstract: Fast recovery (
• Olbright, G. R., & Peyghambarian, N. (1986). Interferometric measurement of the nonlinear index of refraction, n ₂, of CdS_xSe_1-x-doped glasses. Applied Physics Letters, 48(18), 1184-1186.
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  Abstract: A novel technique, which employs a modified Twyman-Green interferometer, is used to measure the nonlinear index of a CdS0.9Se 0.1-doped glass at different wavelengths in the vicinity of the band gap at room temperature. The measured n2 values for the doped glass are compared with calculated values obtained by Kramers-Kronig transformation of the measured Δα(λ)=α(I1,λ)- α(I2,λ). A good agreement is achieved between the measured nonlinear dispersion and that obtained through the Kramers-Kronig relations.
• Peyghambarian, N., Olbright, G. R., Weinberger, D. A., Gibbs, H. M., & Fluegel, B. D. (1986). Resonant two-photon absorption and emission in single-crystal thin films of CuCl. Journal of Luminescence, 35(5), 241-246.
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  Abstract: A comparative study of the luminescence and absorption spectra of excitonic molecules in thin films of cuprous chloride grown on sodium chloride and fused quartz is reported. Thin films of CuCl on NaCl are in single-crystalline form while CuCl on quartz are polycrystalline as evidenced by X-ray diffraction analysis. Under resonant excitation at 7 K, the two-photon absorption spectra for CuCl grown on NaCl exhibit a reduction in linewidth and an increase in the peak absorption as compared with those for CuCl grown on fused silica quartz. Also, the emission lines arising from the decay of excitonic molecules to exciton states are sharper in the single-crystal thin film. These results suggest that the recently grown CuCl single-crystal thin films are substantially superior to polycrystalline thin films for studies of picosecond biexcitonic optical bistability and Bose-condensation of excitonic molecules. © 1986.
• Venkatesan, T., Wilkens, B., Lee, Y. H., Warren, M., Olbright, G., Gibbs, H. M., Peyghambarian, N., Smith, J. S., & Yariv, A. (1986). FABRICATION OF ARRAYS OF GaAs OPTICAL BISTABLE DEVICES.. Applied Physics Letters, 48(2), 145-147.
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  Abstract: Arrays of fast optical bistable devices (OBD') hold excellent promise in the implementation of parallel optical computation systems. The fabrication of an array of 9 multiplied by 9 mu m pixels of OBD's on a GaAs/AlGaAs molecular beam epitaxial layer is reported here. The pixels were defined by reactive ion etching in a freon, helium, and oxygen gas mixture. The array, consisting of over 100 multiplied by 100 devices, formed good quality, uniform interferometers, exhibiting a single fringe in transmitted light. Gate recovery times were reduced by eliminating the top AlGaAs window and by etching 9 multiplied by 9 mu m pixels in an array. Uniform arrays of such high quality optical gates or bistable devices could handle thousands of parallel channels at a rate of several gigahertz per channel.
• Gibbs, H. M., Gibson, U., Peyghambarian, N., Sarid, D., & Stegeman, G. (1985). OPTICAL CIRCUITRY COOPERATIVE.. Proceedings of SPIE - The International Society for Optical Engineering, 517, 150-152.
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  Abstract: An Optical Circuitry Cooperative (OCC) has been formed as an NSF cooperative research center in which six or more companies contribute financial support; NSF provides support which declines to zero in five years. Companies benefit from a center by early access to research results, leverage for their research dollars, participation in research selection, and improved relations with faculty and students. The university receives support for a major research program that increases its research capability, provides reasonably stable funding, and opens more opportunities for graduate students. The areas encompassed by OCC include all-optical logic, picosecond decision-making, guided-wave preprocessors, optical interconnects within computers (both fiber and whole-array imaging), optical storage, and optical computer architecture and devices.
• Gibbs, H. M., Olbright, G. R., Peyghambarian, N., & Haug, H. (1985). KINKS IN INCREASING ABSORPTION OPTICAL BISTABILITY.. Array, 68-69.
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  Abstract: Summary form only given. S. W. Koch et al. (1984) have solved the transport equations for the light intensity and the excitation density for a system that exhibits increasing absorption optical bistability. Under pulse operation a kink in the excitation density is predicted, which moves discontinuously in the beam direction and causes a sawtooth variation in the transmitted intensity. Herein is reported the first observation of these kinks which emphasize the local nature of increasing absorption optical bistability. Kinks illustrate well the intrinsic difference between increasing absorption optical bistability and optical bistability that depends on external feedback, where a longitudinal discontinuity cannot occur.
• Gibbs, H. M., Olbright, G. R., Peyghambarian, N., Schmidt, H. E., Koch, S. W., & Haug, H. (1985). Kinks: Longitudinal excitation discontinuities in increasing absorption optical bistability. Physical Review A, 32(1), 692-694.
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  Abstract: Longitudinal excitation discontinuities (kinks) that arise from partial-sample switching in increasing absorption bistability are predicted theoretically and observed in a sharp-cut color filter. The kinks give rise to a sawtooth output temporal dependence for a triangular input shape. Kinks are an emphatic illustration of the local nature of increasing absorption bistability. © 1985 The American Physical Society.
• Jewell, J. L., Lee, Y. H., Warren, M., Gibbs, H. M., Peyghambarian, N., Gossard, A. C., & Wiegmann, W. (1985). 3-pJ, 82-MHz optical logic gates in a room-temperature GaAs-AlGaAs multiple-quantum-well étalon. Applied Physics Letters, 46(10), 918-920.
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  Abstract: Various pulsed logic functions (nor, xor, etc.) are performed in a high-finesse nonlinear Fabry-Perot étalon containing GaAs-AlGaAs multiple quantum wells at room temperature. Input pulses with energies less than 3 pJ incident on the device produced contrasts greater than 5: 1 in the nor gate, and relaxation times of about 5 ns allowed us to operate the gates at 82 MHz. Thermal stability was demonstrated in the nor gate even though the device was poorly heat sunk.
• Migus, A., Antonetti, A., Hulin, D., Mysyrowicz, A., Gibbs, H. M., Peyghambarian, N., & Jewell, J. L. (1985). ONE-PICOSECOND OPTICAL NOR GATE AT ROOM TEMPERATURE WITH A GaAs-AlGaAs MULTIPLE-QUANTUM-WELL NONLINEAR FABRY-PEROT ETALON.. Applied Physics Letters, 46(1), 70-72.
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  Abstract: The speed of a GaAs-AlGaAs optical logic gate is time resolved using a 100-fs laser system. It shows that the gating operation can be performed in approximately equal to 1 ps, the fastest reported for such a low-energy optical device. The lowest incident switching for such a device is less than or approximately 3 pj.
• Ovadia, S., Gibbs, H. M., Jewell, J. L., Sarid, D., & Peyghambarian, N. (1985). EVIDENCE THAT ROOM TEMPERATURE OPTICAL BISTABILITY IS EXCITONIC IN BOTH BULK AND MULTIPLE-QUANTUM-WELL GALLIUM ARSENIDE.. Optical Engineering, 24(4), 565-568.
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  Abstract: The minimum power ( approximately equals 5 mw) for room-temperature optical bistability is very similar in bulk and multiple-quantum-well (MQW) etalons. No exciton resonance is obvious in the absorption spectrum of bulk GaAs at 300 K because it blends into the band edge, but it is present, and its area is two-thirds that of the MQW heavy-hole exciton. It is shown that the excitonic nonlinear index change is consistent with the observed bistability.
• Peyghambarian, N., & Gibbs, H. M. (1985). OPTICAL BISTABILITY FOR OPTICAL SIGNAL PROCESSING AND COMPUTING.. Optical Engineering, 24(1), 68-73.
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  Abstract: We present the basic principles of optical bistability and summarize the current advances in semiconductor optical switching, with emphasis on recent results in GaAs, CuCl, InAs, InSb, CdS, ZnS, and ZnSe etalons. These devices have great potential for applications involving optical signal processing and computing. We discuss the use of arrays of bistable devices for parallel optical processing and for addressable spatial light modulators. The use of nonlinear etalons as optical gates is also illustrated. To date, GaAs devices have shown the most favorable characteristics for practical applications. They operate at room temperature with a few milliwatts of power using a laser diode as the only light source. Quasi-cw operation and optical fiber signal regeneration have also been demonstrated.
• Sarid, D., Peyghambarian, N., & Gibbs, H. M. (1985). Local-field effect in the biexciton system in CuCl. Physical Review B, 31(6), 4031-4033.
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  Abstract: We show that the inclusion of the local-field effect in the calculation of the nonlinear dielectric function of CuCl near the biexciton resonance does not yield bistability on reflection as suggested by Abram and Maruani. © 1985 The American Physical Society.
• Sarid, D., Peyghambarian, N., & McGinnis, B. P. (1985). OPTICAL BISTABILITY IN THE PRESENCE OF SPATIAL DISPERSION.. IEEE Journal of Quantum Electronics, QE-21(9), 1379-1384.
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  Abstract: The response is calculated of a Fabry-Perot etalon containing a nonlinear excitonic medium in the presence of spatial dispersion. The nonlinearity is taken to be that of the polariton density-dependent collision broadening of the exciton resonance. The effect of spatial dispersion on optical bistability in reflection is investigated theoretically in a CdSe etalon with a high-reflectivity back mirror. 15 refs.
• Berre, M. L., Ressayre, E., Tallet, A., Tai, K., Gibbs, H. M., Rushford, M. C., & Peyghambarian, N. (1984). CONTINUOUS-WAVE OFF-RESONANCE RINGS AND CONTINUOUS-WAVE ON-RESONANCE ENHANCEMENT.. Journal of the Optical Society of America B: Optical Physics, 1(4), 591-605.
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  Abstract: Continuous-wave (cw) off-resonance rings and cw on-resonance enhancement (CORE) are observed as a result of an optical beam propagating through sodium vapor. They are interpreted in terms of diffraction-free encoding (DFE) followed by free-space propagation. They are discussed with respect to the three regimes of DFE, namely, pure phase encoding, on-resonance pure amplitude encoding leading to stripping, and the intermediate case involving both phase and amplitude encodings. First there are far-field interference rings displaying pure phase encoding. They are observed on both sides of resonance, as expected by theory. Second, there is CORE, which is a Fresnel diffraction manifestation resulting from the stripping of the beam profile by the nonlinear medium, and in the far field, the corresponding Fraunhofer patterns.
• Jewell, J. L., Lee, Y. H., Warren, M., Rushford, M. C., Gibbs, H. M., Peyghambarian, N., Gossard, A. C., & Wiegmann, W. (1984). OPTICAL LOGIC IN GaAs FABRY-PEROT ETALONS.. Array, 156-157.
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  Abstract: We report a technique for operating a single nonlinear Fabry-Perot etalon which yields the decisions NOR, NAND, XOR, OR, and AND, simultaneously if desired, and with minimum time and energy per cycle. The transmission vs. time characteristics obtained from experiments with dye-filled and GaAs etalons qualitatively verify a computer simulation.
• Jewell, J. L., Ovadia, S., Peyghambarian, N., Tarng, S. S., Gibbs, H. M., Gossard, A. C., & Wiegmann, W. (1984). ROOM-TEMPERATURE EXCITONIC OPTICAL BISTABILITY IN BULK GaAs.. Array, 120-122.
• Jewell, J. L., Rushford, M. C., Gibbs, H. M., & Peyghambarian, N. (1984). SINGLE-ETALON OPTICAL LOGIC GATES.. Array, 184-185.
• Olbright, G. R., Peyghambarian, N., Gibbs, H. M., MacLeod, H. A., & Milligen, F. V. (1984). Microsecond room-temperature optical bistability and crosstalk studies in ZnS and ZnSe interference filters with visible light and milliwatt powers. Applied Physics Letters, 45(10), 1031-1033.
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  Abstract: ZnS and ZnSe interference filters exhibit fast switch-on times (10 and 50 μs, respectively) with milliwatt powers at room temperature. The nonlinearity in the refractive index is found to result from heating by absorption. Crosstalk between two light beams is negligible for separations exceeding 20 μm with 7.7-μm beam diameters.
• Peyghambarian, N. (1984). OPTICAL BISTABILITY: A NOVEL APPROACH TO OPTICAL SIGNAL PROCESSING AND COMMUNICATIONS.. NASA Conference Publication, 135-148.
• Peyghambarian, N., Gibbs, H. M., Jewell, J. L., Antonetti, A., Migus, A., Hulin, D., & Mysyrowicz, A. (1984). Blue shift of the exciton resonance due to exciton-exciton interactions in a multiple-quantum-well structure. Physical Review Letters, 53(25), 2433-2436.
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  Abstract: Femtosecond time-resolved dynamics of exciton screening and pairing is studied in a 53- GaAs multiple-quantum-well structure at 15 and 224 K. An intriguing high-energy shift of the exciton self-energy in the dense limit is reported. © 1984 The American Physical Society.
• Peyghambarian, N., Sarid, D., Gibbs, H. M., Chase, L. L., & Mysyrowicz, A. (1984). Collision broadening model for the biexciton resonance in CuCl. Optics Communications, 49(2), 125-128.
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  Abstract: It is shown that the cage model of the spectral broadening of the biexciton resonance in CuCl due to collisions is in agreement with experimental results. © 1984.
• Tai, K., Gibbs, H. M., Rushford, M. C., Peyghambarian, N., LeBerre, M., Ressayre, E., & Tallet, A. (1984). OBSERVATION OF CONTINUOUS-WAVE ON-RESONANCE ENHANCEMENT.. Array, 76-77.
• Tarng, S. S., Gibbs, H. M., Jewell, J. L., Peyghambarian, N., Gossard, A. C., Venkatesan, T., & Wiegmann, W. (1984). USE OF A DIODE LASER TO OBSERVE ROOM-TEMPERATURE, LOW-POWER OPTICAL BISTABILITY IN A GaAs-AlGaAs ETALON.. Applied Physics Letters, 44(4), 360-361.
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  Abstract: Optical bistability is observed using a single-mode diode laser in a GaAs-AlGaAs multiple-quantum-well etalon with as low as six mw power at 830 nm.
• Peyghambarian, N., Chase, L. L., & Mysyrowicz, A. (1983). Bose-Einstein statistical properties and condensation of excitonic molecules in CuCl. Physical Review B, 27(4), 2325-2345.
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  Abstract: A comprehensive investigation of the optical properties of excitonic molecules in CuCl films is presented and discussed. The experimental work includes resonant two-photon absorption (TPA), observations of the resonantly excited biexciton emission, and optical pump-and-probe studies. The collision broadening of the TPA implies a collision rate ∼10-12 sec for the biexcitons, which is sufficiently rapid to establish a quasithermal equilibrium for the particles on a time scale that is short in comparison with the biexciton lifetime and the duration of the laser pump pulse. The biexciton luminescence line shapes obtained with resonant k→=0 two-photon excitation have been fitted using a Bose-Einstein thermal distribution of biexcitons. The chemical potential obtained from the fits goes to zero as the biexciton density is increased at a fixed lattice temperature or if the lattice temperature is decreased at fixed density. The sharp luminescence features that are observed at high densities and low temperatures with single-beam, two-photon excitation are interpreted as resulting from a Bose-Einstein-condensed state of the biexcitons at twice the wave vector of the laser pumping photons. Further evidence for a condensed state is obtained from optical-probe measurements in which a small number of probe biexcitons is injected into the sample, with and without the presence of a condensed state produced by an intense laser pump beam. The luminescence of these injected probe biexcitons is modified in the presence of the pump beam such that it exhibits the sharp features of the emission from the condensed state. Measurements of optical gain and stimulated emission in the presence of the pump beam show that the redistribution of the probe luminescence does not result from those processes, but must involve a preferential redistribution of the probe particles in momentum space via collisions. Such a redistribution is expected when additional particles are added to a condensed system of bosons. © 1983 The American Physical Society.
• Peyghambarian, N., Chase, L. L., & Mysyrowicz, A. (1983). Momentum-space condensation of probe-injected biexcitons into a strongly pumped biexciton state in CuCl. Physica B+C, 117-118(PART 1), 299-300.
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  Abstract: Two sets of new results are presented which confirm the occurrence of a Bose-Einstein condensation of biexcitons in CuCl. First, luminescence spectra recorded under well controlled conditions yield the distribution function of the particles, which takes the form of a strongly degenerate Bose-Einstein distribution under increasing excitation, with γ up to 0. Second, probe particles injected into the system in the presence of the presumed condensate are observed to coalesce into it. © 1983.
• Peyghambarian, N., Gibbs, H. M., Rushford, M. C., & Weinberger, D. A. (1983). Observation of biexcitonic optical bistability and optical limiting in CuCl. Physical Review Letters, 51(18), 1692-1695.
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  Abstract: Experimental evidence for the occurrence of optical bistability using the biexciton two-photon resonance in CuCl is presented. These observations agree with recent theoretical predictions that require an intensity of 10 MW/cm2 and 10-μm-thick etalons with 90% reflective coatings. Earlier much less demanding predictions neglected two important physical effects: unsaturable background absorption at the biexciton from the tail of the exciton resonance and broadening of the biexciton resonance with intensity. © 1983 The American Physical Society.
• Sarid, D., Peyghambarian, N., & Gibbs, H. M. (1983). Analysis of biexcitonic optical bistability in CuCl in the presence of collision broadening. Physical Review B, 28(2), 1184-1186.
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  Abstract: The dielectric function of CuCl in the presence of biexciton formation that involves collision-broadening effects is analyzed in terms of incident photon energy and intensity. We discuss the nonlinear response of the material and its application to bistable devices. © 1983 The American Physical Society.
• Peyghambarian, N., Chase, L. L., & Mysyrowicz, A. (1982). Biexciton resonance linewidth in CuCl: Collision broadening or not?. Optics Communications, 42(1), 51-54.
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  Abstract: The width of the biexciton two-photon resonance in CuCl, as measured with weak probe beams, shows a marked broadening if a high density of biexcitons is injected with an intense pump beam. These results are attributed to collisions between excitonic particles. © 1982.
• Peyghambarian, N., Chase, L. L., & Mysyrowicz, A. (1982). MOMENTUM-SPACE CONDENSATION OF PROBE-INJECTED BIEXCITONS INTO A STRONGLY PUMPED BIEXCITON STATE IN CuCl.. Physica B: Physics of Condensed Matter & C: Atomic, Molecular and Plasma Physics, Optics, 117-118(Pt I), 299-300.
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  Abstract: Two sets of new results are presented which confirm the occurrence of a Bose-Einstein condensation of biexcitons in CuCl. First, luminescence spectra recorded under well controlled conditions yield the distribution function of the particles, which takes the form of a strongly degenerate Bose-Einstein distribution under increasing excitation, with mu up to 0. Second, probe particles injected into the system in the presence of the presumed condensate are observed to coalesce into it.
• Peyghambarian, N., Chase, L. L., & Mysyrowicz, A. (1982). Momentum-space condensation of probe biexcitons into a pumped state in CuCl. Optics Communications, 41(3), 178-181.
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  Abstract: Biexcitons injected at zero momentum into a CuCl film are observed to scatter preferentially into a strongly pumped state at a finite wavevector. These results imply the existence of a Bose-condensed state, at least in the presence of the laser pumping. © 1982.
• Chase, L. L., Peyghambarian, N., Grynberg, G., & Mysyrowicz, A. (1979). Direct creation of a high density of biexcitons at K =0 in CuCl. Optics Communications, 28(2), 189-192.
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  Abstract: The two-photon absorption corresponding to the creation of a large number of biexcitons with zero momentum is studied in CuCl at 4.2 K. The power dependence of the absorption linewidth suggests liquid-like collisions between the biexcitons. The emission spectrum of the biexcitons produced at K=0 is also presented. © 1979.
• Chase, L. L., Peyghambarian, N., Grynberg, G., & Mysyrowicz, A. (1979). Evidence for bose-einstein condensation of biexcitons in CuCl. Physical Review Letters, 42(18), 1231-1234.
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  Abstract: Evidence for the occurrence of a Bose-Einstein condensation of biexcitons in evaporated CuCl films is reported. It involves several unusual properties of the molecular luminescence under strong excitation. © 1979 The American Physical Society.

Proceedings Publications

• Peyghambarian, N. N. (2021). An Automated Phoropter System for Objective, Accurate, and Rapid Assessment of the Visual Acuity. In Bio-Optics: Design and Application 2021.
• Peyghambarian, N. N. (2020, see attached file). see attached file. In see attached file.
• Peyghambarian, N. N. (2019, see attached file). see attached file. In see attached file.
• Peyghambarian, N. N. (2018, See attached file). See attached file. In See attached file.
• Amirsolaimani, B., Peyghambarian, N. N., Schwiegerling, J. T., Bablumyan, A., Savidis, N., & Peyman, G. (2017, August). An automatic holographic adaptive phoropter. In SPIE Nanoscience and engineering 2017, 10352, 1035208.
• Peyghambarian, N. N. (2017, April 2017). High power all fiber-based ultrafast lasers. In SPIE Fiber Lasers XIV: Technology and Systems, 10083.
• Peyghambarian, N. N. (2017, August 2017). An automatic holographic adaptive phoropter. In SPIE Biosensing and Nanomedicine X.
• Peyghambarian, N. N. (2017, February 2017). Relaxed tolerance adiabatic silicon coupler for high I/O port-density optical interconnects. In SPIE Integrated Optics: Devices, Materials, and Technologies XXI, 10106.
• Peyghambarian, N. N. (2016, see attached). see attached. In see attached.
• Thamvichai, R., Blanche, P. A., Norwood, R. A., Wissinger, J. W., Neifeld, M. A., & Peyghambarian, N. N. (2016, 10/2016). Optical Implementation of Probabilistic Graphical Models. In Rebooting Computing (ICRC), IEEE International Conference on.
• Peyghambarian, N. N. (2015, see attachment). see attachment. In see attachment.
• Peyghambarian, N. N. (2014, see attachment). see attachment. In see attachment.

Presentations

• Peyghambarian, N. N. (2022). Quantum receiver enhanced by adaptive learning. Conference on Lasers and Electro-Optics (CLEO). San Jose.
• Peyghambarian, N. N. (2017, May 2017). Diode-pumped CNT Mode-locked Ho3+-doped Fluoride Fiber Laser at 1.2 µm. CLEO: Science and Innovations.
• Peyghambarian, N. N. (2017, May 2017). Investigation of double-clad Yb3+-doped phosphate fiber for 976 nm single-frequuency laser amplification. CLEO: Science and Innovations.
• Peyghambarian, N. N. (2017, May 2017). Octave-spanning dual-comb spectroscopy with a free-running bidirectional mode-locked femtosecond fiber laser. CLEO Science and Innovations.