Thomas D Milster

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Scholarly Contributions

Chapters

• Milster, T. D. (2020). The Gerchberg-Saxton Phase Retrieval Algorithm and Related Variations. In Optical Holography(pp 61--72). Elsevier.
• Milster, T. D., Butz, J., Nakano, T., Tominaga, J., & Bletscher, W. (2003). Signal Power in the Angular Spectrum of AgOx SuperRENS Media. In Optical Nanotechnologies: The Manipulation of Surface and Local Plasmons. Springer, Berlin, Heidelberg. doi:10.1007/3-540-45871-9_9
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  Light-scattering properties of super-RENS media are examined in the angular spectrum near the objective lens of an optical data storage device. Signal distributions resulting from mark patterns below the resolution limit, at the resolution limit and above the resolution limit are analyzed in order to understand better the mechanism of super-RENS resolution enhancement. Results from a combination of scalar and vector modeling tools are compared to measurements from a dynamic spin stand. Simulations assume that the super-RENS effect is generated from a circular Ag region that follows the focused spot as the medium moves underneath it.
• Myers, K. J., Barrett, H. H., Barrett, H. H., Borgstrom, M. C., Cargill, E. B., Clough, A. V., Clough, A. V., Fiete, R. D., Milster, T. D., Patton, D. D., Paxman, R. G., Seeley, G. W., Smith, W. E., Stempski, M. O., & Milster, T. D. (1986). A Systematic Approach to the Design of Diagnostic Systems for Nuclear Medicine. In nformation Processing in Medical Imaging: Proceedings of the 9th conference. Springer, Dordrecht. doi:10.1007/978-94-009-4261-5_30
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  Diagnostic radiology has traditionally been based on the evaluation of images by human observers, but neither an image nor a human is absolutely essential to the problem. The best diagnostic system is not necessarily one that produces pleasing images or has a good MTF or good signal-to-noise ratio (SNR). Rather, the only meaningful measure of system performance is the correctness of the final diagnosis. The central question in system design is: How can one collect the best data set with which to make a diagnosis? To even attempt to answer this question, we must first decide what organs and what diseases are to be studied by a system or, in other words, what the precise task of the system is. In addition, a careful definition of “best” must be given. Finally, some strategy must be defined for realizing the best data-collection system. It is our purpose to show that such a systematic approach to total system design is possible in principle (although very difficult in practice), and to summarize current efforts at the University of Arizona towards realization of this goal.

Journals/Publications

• Esparza, M., Choi, H., Brar, N., Wang, Z., Kim, Y., Fellows, C., Bog, M., Kim, G., Yi, A., Milster, T. D., & others, . (2023). Kinematically engaged yoke system for segmented lens-based space telescope integration and testing. Journal of the European Optical Society-Rapid Publications, 19(1), 2023016.
• Apai, D., Milster, T. D., Kim, D., Bixel, A., Schneider, G., Rackham, B., & Arenberg, J. (2021). A Search for Life in a Thousand Earths: The Nautilus Space Observatory. Bulletin of the American Astronomical Society, 53(3), 1206.
• Milster, T. D., Wang, Z., & Kim, Y. S. (2021). Design aspects of large-aperture MODE lenses. OSA Continuum, 4(1), 171--181.
• Wang, Z., Kim, Y., & Milster, T. D. (2021). High-harmonic diffractive lens color compensation. Applied optics, 60(19), D73--D82.
• Finan, E., & Milster, T. (2020). Phase retrieval and adaptive optics correction for systems with diffractive surfaces. Applied optics, 59(22), G92--G98.
• Milster, T. D., Kim, Y. S., Wang, Z., & Purvin, K. (2020). Multiple-order diffractive engineered surface lenses. Applied optics, 59(26), 7900--7906.
• Zhang, Y., Liang, R., Spires, O. J., Yin, S., Yi, A., & Milster, T. D. (2020). Precision glass molding of diffractive optical elements with high surface quality. Optics Letters, 45(23), 6438--6441.
• Apai, D., Milster, T. D., Kim, D. W., Bixel, A., Schneider, G., Liang, R., & Arenberg, J. (2019). A Thousand Earths: A Very Large Aperture, Ultralight Space Telescope Array for Atmospheric Biosignature Surveys. ASTRONOMICAL JOURNAL, 158(2).
• Apai, D., Milster, T. D., Kim, D. W., Bixel, A., Schneider, G., Liang, R., & Arenberg, J. (2019). A Thousand Earths: A Very Large Aperture, Ultralight Space Telescope Array for Atmospheric Biosignature Surveys. Astronomical Journal, 158(83), 83. doi:10.3847/1538-3881/ab2631
• Eguchi, A., & Milster, T. D. (2019). Single-shot phase retrieval with complex diversity. OPTICS LETTERS, 44(21), 5108-5111.
• Eguchi, A., Brewer, J., & Milster, T. D. (2019). Optimization of random phase diversity for adaptive optics using an LCoS spatial light modulator. APPLIED OPTICS, 58(25), 6834-6840.
• Apai, D., Milster, T. D., Arenberg, J., Kim, D., Liang, R., Bixel, A., Fellows, C., & Grunsfeld, J. (2018). Nautilus Deep Space Observatory: A Giant Segmented Space Telescope Array for a Galactic Biosignature Survey. LPI Contributions, 2063.
• Bendek, E., Belikov, R., Guyon, O., Greene, T., Pluzhnik, E., Milster, T., Rodack, A., Finan, E., & Knight, J. (2018). TDEM final report: Enhanced direct imaging exoplanet detection with astrometry mass determination. arXiv preprint arXiv:1805.06933.
• Gao, W., & Milster, T. (2018). Strehl ratio for optical systems with ultrafast illumination. Optics express, 26(14), 18028--18042.
• Gao, W., Finan, E., Kim, G., Kim, Y., & Milster, T. D. (2018). Optical design and system characterization of an imaging microscope at 121.6 nm. Optical Engineering, 57(3), 035101.
• Ajdaharian, J., Saikaly, V., Ngo, W., Krasieva, T., Milster, T., & Wilder-Smith, P. (2015). MALIGNANT CHANGE AND MARGINS: NOVEL MINIATURIZED PROBES IN THE QUEST FOR MARKERS OF MALIGNANCY. LASERS IN SURGERY AND MEDICINE, 47, 1.
• Pacheco, S., Brand, J. F., Zaverton, M., Milster, T., & Liang, R. (2015). Sensitivity analysis and optimization method for the fabrication of one-dimensional beam-splitting phase gratings. OPTICS EXPRESS, 23, 11771-11782.
• Pacheco, S., Milster, T., & Liang, R. (2015). Analysis of grating doublets for achromatic beam-splitting. OPTICS EXPRESS, 23, 22939-22952.
• Pacheco, S., Salahieh, B., Milster, T. D., Rodriguez, J. J., & Liang, R. (2015). Transfer Function Analysis in Epi-Illumination Fourier Ptychography. Optics Letters, 40(22), 5343-5346.
• Pacheco, S., Salahieh, B., Milster, T., Rodriguez, J. J., & Liang, R. (2015). Transfer function analysis in epi-illumination Fourier ptychography. OPTICS LETTERS, 40, 5343-5346.
• Ament, C., Johnson, L., Schmitt-Sody, A., Lucero, A., Milster, T., & Polynkin, P. (2014). Generation of multiterawatt vortex laser beams. Appl. Opt., 53(15), 3355--3360.
• Pacheco, S., Milster, T., Zhou, J., & Liang, R. (2014). System design and evaluation of the array confocal fluorescence microscope. Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 8936.
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  Abstract: The scanning speed for conventional confocal fluorescence imaging systems is limited due to several factors. To improve the speed of scanning, we develop an array confocal fluorescence microscope (ACFM) that can image large 3D volumes faster than conventional confocal microscopes over a large field of view (FOV). This paper will discuss the design and evaluation of the array confocal fluorescence microscope. © 2014 SPIE.
• Sierchio, J. M., Zaverton, M., Johnson, L., Densmore, V., & Milster, T. (2014). Central aperture detection for auto direct read-write photoresist fabrication and inspection. Optical Engineering, 53(8), 084104--084104.
• Milster, T. D., Kim, Y., & Phat, L. u. (2013). Hyper-NA(NA = 2.8)microscope using 1.55um fs source for multi-photon imaging. Bio-Optics: Design and Application, BODA 2013, BTuD1.
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  Abstract: A new microscope is discussed, where scanning illumination consists of NA = 2.8 with a λ= 1.55μm fs fiber laser. Near-infrared 2P collection is imaged with NA = 1.2. Biological applications are considered. Optics in the Life Sciences Congress Technical Digest © 2013 The Optical Society (OSA).
• Summitt, C., Wang, S., Johnson, L., Zaverton, M., Milster, T., & Takashima, Y. (2013). Flexible micro-optics fabrication by direct laser writing toward CMOS compatible 3D optical circuit. Proceedings of SPIE - The International Society for Optical Engineering, 8613.
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  Abstract: We demonstrated a 45 degree micro mirror by a direct laser writing method. A flat, smooth and clearly defined mirror surface has been fabricated despite of the finite size and long tail of the point spread function of the exposure tool. © 2013 Copyright SPIE.
• Park, J. R., Sierchio, J., Zaverton, M., Kim, Y., & Milster, T. D. (2012). Characterization of photoresist and simulation of a developed resist profile for the fabrication of gray-scale diffractive optic elements. Optical Engineering, 51(2).
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  Abstract: We have characterized a photoresist used for the fabrication of gray-scale diffractive optic elements in terms of Dill's and Mack's model parameters. The resist model parameters were employed for the simulations of developed resist profiles for sawtooth patterns executed by solving the Eikonal equation with the fast-marching method. The simulated results were shown to be in good agreement with empirical data. © 2012 Society of Photo-Optical Instrumentation Engineers.
• George, A., & Milster, T. D. (2011). Spot distribution measurement using a scanning nanoslit. Applied Optics, 50(24), 4746-4754.
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  PMID: 21857697;Abstract: A scanning and rotating nanoslit is used to measure submicrometer features in focused spot distributions. Using a filtered backprojection technique, a highly accurate reconstruction is demonstrated. Experimental results are confirmed by simulating the scanning slit technique using a physical optics simulation program. Analysis of various error mechanisms is reported, and the reconstruction algorithm is determined to be very resilient. The slit is 125nm wide and 50 μm long and is fabricated on a 120nm thick layer of aluminum. The size of the image field is 15 μm, and simulations indicate that 200nm Rayleigh resolution is possible with an infinitely narrow slit. © 2011 Optical Society of America.
• Kim, Y., & Milster, T. D. (2011). Hyper numerical aperture blu-ray disc recording. Optics InfoBase Conference Papers.
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  Abstract: We develop a hyper numerical aperture Blu-ray disc(HBD) recording system with a solid immersion lens. We use a phase change recording media with a 100 μm cover-layer. The HBD pick-up consists of a solid immersion lens with a numerical aperture of 1.41 and a laser diode of 408nm wavelength. © 2011 OSA.
• Milster, T., George, A., & Milster, T. D. (2011). Spot distribution measurement using a scanning nanoslit. Applied optics, 50(24).
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  A scanning and rotating nanoslit is used to measure submicrometer features in focused spot distributions. Using a filtered backprojection technique, a highly accurate reconstruction is demonstrated. Experimental results are confirmed by simulating the scanning slit technique using a physical optics simulation program. Analysis of various error mechanisms is reported, and the reconstruction algorithm is determined to be very resilient. The slit is 125 nm wide and 50 μm long and is fabricated on a 120 nm thick layer of aluminum. The size of the image field is 15 μm, and simulations indicate that 200 nm Rayleigh resolution is possible with an infinitely narrow slit.
• Murray, I. B., Densmore, V., Bora, V., Pieratt, M. W., Hibbard, D. L., & Milster, T. D. (2011). Numerical comparison of grid pattern diffraction effects through measurement and modeling with OptiScan software. Proceedings of SPIE - The International Society for Optical Engineering, 8016.
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  Abstract: Coatings of various metalized patterns are used for heating and electromagnetic interference (EMI) shielding applications. Previous work has focused on macro differences between different types of grids, and has shown good correlation between measurements and analyses of grid diffraction. To advance this work, we have utilized the University of Arizona's OptiScan software, which has been optimized for this application by using the Babinet Principle. When operating on an appropriate computer system, this algorithm produces results hundreds of times faster than standard Fourier-based methods, and allows realistic cases to be modeled for the first time. By using previously published derivations by Exotic Electro-Optics, we compare diffraction performance of repeating and randomized grid patterns with equivalent sheet resistance using numerical performance metrics. Grid patterns of each type are printed on optical substrates and measured energy is compared against modeled energy. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
• George, A., & Milster, T. D. (2010). Characteristics of a scanning nano-slit image sensor for line-and-space patterns. Applied Optics, 49(19), 3821-3830.
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  PMID: 20648152;Abstract: A single scanning nano-slit is used to study aerial image characteristics. Finite-difference time-domain simulations reveal that, in the far field of such a slit, the detected image contrast is very high over a large spatial frequency range regardless of the polarization direction. In the near field, the TM polarization shows a decrease in contrast at larger spatial frequencies. Experiments verify this characteristic using a 125nm wide slit on an aluminum mask at a wavelength of 658nm. Unlike the light transmission characteristics of a nano-slit, which are greatly influenced by slit width and metal mask thickness, it is shown that image contrast measurement is almost insensitive to small changes in these parameters. It is found that defects on the metal mask play an important role in accurate analysis of the system. © 2010 Optical Society of America.
• Kim, J., Kim, M., Hong, S., & Milster, T. D. (2010). Characteristics of the depth of focus in a high-NA optical system with a SIAX for data storage. Proceedings of SPIE - The International Society for Optical Engineering, 7730.
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  Abstract: We study the tolerance characteristic of SIAX and suggest a newly designed SIL-Axicon system for the better tolerances. Methods for checking beam quality, optimization and remaining problems are suggested. SIL-Axicon system shows more tolerances in the uniformity of beam incident angle. Bessel beam (BB) with SIL can be used for multi layer high density data storage systems. We study the tolerance characteristic of SIAX and suggest a newly designed SIL-Axicon system for the better tolerances. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Milster, T., George, A., & Milster, T. D. (2010). Characteristics of a scanning nano-slit image sensor for line-and-space patterns. Applied optics, 49(19).
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  A single scanning nano-slit is used to study aerial image characteristics. Finite-difference time-domain simulations reveal that, in the far field of such a slit, the detected image contrast is very high over a large spatial frequency range regardless of the polarization direction. In the near field, the TM polarization shows a decrease in contrast at larger spatial frequencies. Experiments verify this characteristic using a 125 nm wide slit on an aluminum mask at a wavelength of 658 nm. Unlike the light transmission characteristics of a nano-slit, which are greatly influenced by slit width and metal mask thickness, it is shown that image contrast measurement is almost insensitive to small changes in these parameters. It is found that defects on the metal mask play an important role in accurate analysis of the system.
• Milster, T., Tamkin, J. M., & Milster, T. D. (2010). Effects of structured mid-spatial frequency surface errors on image performance. Applied optics, 49(33).
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  Optical designers are encouraged to adopt aspheric and free-form surfaces into an increasing number of design spaces because of their improved performance. However, residual tooling marks from advanced aspheric fabrication techniques are difficult to remove. These marks, typically in the mid-spatial frequency (MSF) regime, give rise to structured image artifacts. Using a theory developed in previous publications, this paper applies the fundamentals of MSF modeling to demonstrate how MSF errors are evaluated and toleranced in an optical system. Examples of as-built components with MSF errors are analyzed using commercial optical design software.
• Milster, T., Tamkin, J. M., Dallas, W. J., & Milster, T. D. (2010). Theory of point-spread function artifacts due to structured mid-spatial frequency surface errors. Applied optics, 49(25).
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  Optical design and tolerancing of aspheric or free-form surfaces require attention to surface form, structured surface errors, and nonstructured errors. We describe structured surface error profiles and effects on the image point-spread function using harmonic (Fourier) decomposition. Surface errors over the beam footprint map onto the pupil, where multiple structured surface frequencies mix to create sum and difference diffraction orders in the image plane at each field point. Difference frequencies widen the central lobe of the point-spread function and summation frequencies create ghost images.
• Milster, T., Zhang, J., Kim, Y., Yang, S., & Milster, T. D. (2010). Illumination artifacts in hyper-NA vector imaging. Journal of the Optical Society of America. A, Optics, image science, and vision, 27(10).
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  Off-axis polarized monopole illumination is applied to a hyper-numerical-aperture (NA) (NA>1) microscopic system. Illumination artifacts due to vector effects are observed, which are asymmetric and depend on illumination conditions. A model based on rigorous coupled wave theory is used to simulate image profiles for dielectric, semiconductor, and metal gratings with different monopole locations and polarization states. A solid immersion lens microscope is used to image different types of samples including MoSi photomask, patterned silicon wafer, and chrome photomask. The experimental images are in good agreement with simulation results.
• Park, J. R., Kim, Y., Zaverton, M., Sierchio, J., & Milster, T. D. (2010). Characterization of photoresist and study on developed resist profile for the fabrication of gray-scale diffractive optic elements. Optics InfoBase Conference Papers.
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  Abstract: We have characterized photoresist used for fabrication of gray-scale diffractive optic elements using Dill's and Mack's parameters. Using the fast-marching method, simulations of resist profiles have been shown to match experimental results. © 2010 Optical Society of America.
• Tamkin, J. M., & Milster, T. D. (2010). Analysis and tolerancing of structured mid-spatial frequency errors in imaging systems. Proceedings of SPIE - The International Society for Optical Engineering, 7652.
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  Abstract: Structured mid-spatial frequency surface errors on aspheric optics can create ghost images and reduced contrast. This reduction in performance is shown to be non-linear with surface height using Fourier methods without small signal or statistical approximations. Tolerancing MSF errors can use traditional MTF metrics, and derives peak-to-valley limits on MSF surface height components. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Tamkin, J. M., & Milster, T. D. (2010). Effects of structured mid-spatial frequency surface errors on image performance. Applied Optics, 49(33), 6522-6536.
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  PMID: 21102679;Abstract: Optical designers are encouraged to adopt aspheric and free-form surfaces into an increasing number of design spaces because of their improved performance. However, residual tooling marks from advanced aspheric fabrication techniques are difficult to remove. These marks, typically in the mid-spatial frequency (MSF) regime, give rise to structured image artifacts. Using a theory developed in previous publications, this paper applies the fundamentals of MSF modeling to demonstrate how MSF errors are evaluated and toleranced in an optical system. Examples of as-built components with MSF errors are analyzed using commercial optical design software. © 2010 Optical Society of America.
• Tamkin, J. M., & Milster, T. D. (2010). Point spread function artifacts from structured mid-spatial frequency errors. Optics InfoBase Conference Papers.
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  Abstract: Structured mid-spatial frequency surface errors on aspheric optics can create ghost images and reduced contrast. This reduction in performance is shown to be non-linear with surface height using Fourier methods and plane wave spectrum analysis. © OSA/IODC/OF&T 2010.
• Tamkin, J. M., Dallas, W. J., & Milster, T. D. (2010). Theory of point-spread function artifacts due to structured mid-spatial frequency surface errors. Applied Optics, 49(25), 4814-4824.
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  PMID: 20820225;Abstract: Optical design and tolerancing of aspheric or free-form surfaces require attention to surface form, structured surface errors, and nonstructured errors. We describe structured surface error profiles and effects on the image point-spread function using harmonic (Fourier) decomposition. Surface errors over the beam footprint map onto the pupil, where multiple structured surface frequencies mix to create sum and difference diffraction orders in the image plane at each field point. Difference frequencies widen the central lobe of the point-spread function and summation frequencies create ghost images. © 2010 Optical Society of America.
• Tamkin, J. M., Milster, T. D., & Dallas, W. (2010). Theory of modulation transfer function artifacts due to mid-spatial-frequency errors and its application to optical tolerancing. Applied Optics, 49(25), 4825-4835.
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  PMID: 20820226;Abstract: Aspheric and free-form surfaces are powerful surface forms that allow designers to achieve better performance with fewer lenses and smaller packages. Unlike spheres, these surfaces are fabricated with processes that leave a signature, or "structure," that is primarily in the mid-spatial-frequency region. These structured surface errors create ripples in the modulation transfer function (MTF) profile. Using Fourier techniques with generalized functions, the drop in MTF is derived and shown to exhibit a nonlinear relationship with the peak-to-valley height of the structured surface error. © 2010 Optical Society of America.
• Yang, S., Milster, T., Park, J. R., & Zhang, J. (2010). High-numerical-aperture image simulation using Babinet's principle. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 27(5), 1012-1023.
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  PMID: 20448767;Abstract: Simulation techniques are developed for high-numerical-aperture (NA) polarized microscopy with Babinet's principle, including partial coherence and vector diffraction for non-periodic geometries. The model includes vector illumination and diffraction in high-NA (up to NA=3.5) object space that is imaged into low-NA image space and recorded on an image sensor. A mathematical model for the Babinet approach is developed and interpreted that includes partial coherence using expanded mutual intensity, where object reflective characteristics modify the coherence functions. Simulation results of the Babinet's principle approach are compared with those of rigorous coupled wave theory (RCWT) for periodic structures to investigate the accuracy of this approach and its limitations. © 2010 Optical Society of America.
• Yang, S., Milster, T., Zhang, J., & Chen, T. (2010). Characteristics of evanescent polarization imaging. Journal of Modern Optics, 57(9), 783-797.
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  Abstract: A technique for obtaining native (uncrossed illumination/image polarizations) and induced (crossed illumination/image polarization) using a significant amount of evanescent energy is described for a solid immersion lens (SIL) microscope. Characteristics of native and induced polarization images for different object structures and materials are studied in detail. Experiments are conducted with a NA = 1.48 at λ = 550 nm microscope. Near-field images are simulated and analyzed with an RCWT approach. Contrast curve versus object spatial frequency calculations are compared with experimental measurements. Dependencies of contrast versus source polarization angles and air gap for native and induced polarization image profiles are evaluated. By using the relationship between induced polarization and topographical structure, an induced polarization image of an alternating phase shift mask (PSM) is converted into a topographical image, which shows very good agreement with atomic force microscope (AFM) measurement. Images of other material structures include a dielectric grating, chrome-on-glass grating, silicon CPU structure, BD-R and BD-ROM. © 2010 Taylor & Francis.
• Zaverton, M., Sierchio, J., Kim, Y. S., Hansen, D., Bletcher, W., Tamkin, J., & Milster, T. D. (2010). Maskless lithography tool for fabrication and inspection of diffractive optical elements and computer generated holograms. Optics InfoBase Conference Papers.
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  Abstract: A high-speed maskless lithography tool is described for fabricating diffractive optical elements and computer generated holograms. The system has the capability to write gray-scale features is also used for inspection of the sample after fabrication. © 2010 OSA.
• Zhang, J., Kim, Y., Yang, S., & Milster, T. D. (2010). Illumination artifacts in hyper-NA vector imaging. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 27(10), 2272-2284.
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  PMID: 20922018;Abstract: Off-axis polarized monopole illumination is applied to a hyper-numerical-aperture (NA) (NA>1) microscopic system. Illumination artifacts due to vector effects are observed, which are asymmetric and depend on illumination conditions. A model based on rigorous coupled wave theory is used to simulate image profiles for dielectric, semiconductor, and metal gratings with different monopole locations and polarization states. A solid immersion lens microscope is used to image different types of samples including MoSi photomask, patterned silicon wafer, and chrome photomask. The experimental images are in good agreement with simulation results. © 2010 Optical Society of America.
• Zhang, J., Yang, S., Kim, Y., Milster, T. D., & Park, J. R. (2010). Microscope system for Blu-ray disc samples. Applied Optics, 49(36), 6878-6887.
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  PMID: 21173821;Abstract: We introduce a microscope system using a solid immersion lens (SIL) to image Blu-ray disc samples without removing the protective cover layer. The aberration caused by the cover layer is minimized with a truncated SIL. A subsurface imaging simulation is achieved by using the rigorous coupled wave theory, partial coherence, vector diffraction, and the Babinet principle. Simulated results are compared with experimental images and atomic force microscopy measurements. © 2010 Optical Society of America.
• Zhang, J., Yang, S., Milster, T. D., Bletscher, W., & Hansen, D. (2010). Hyper-NA imaging with solid-immersion optics and induced polarization imaging. Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 7570.
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  Abstract: Solid immersion lens (SIL) is used in microscopic systems for hyper numerical aperture (NA) imaging. The NA of the SIL microscope can be larger than 2 by using the high refractive index SIL. In this paper, examples of hyper-NA (NA>1.4) imaging are illustrated, including a normal SIL microscope for imaging samples like CPU chips, photomasks which have no cover layer and a special SIL microscope for imaging samples like Blu-Ray optical discs which have cover layer to protect the pattern. In both cases, good contrast images can be achieved by minimizing the system aberration. At the end, characteristics of induced polarization imaging (imaging through crossed polarizers) and a twostep solid immersion lens using Gallium Phosphide (GaP) (NA∼2) are discussed. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Dallas, W. J., Milster, T. D., Blanche, P., Friedman, A. C., Roehrig, H., & Krupinski, E. A. (2009). Computer-generated holographic stereograms. Optics InfoBase Conference Papers.
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  Abstract: We examine one type of holographic stereogram and its implementation on two widely different media. The first medium is photoresist for a conventional computer-generated hologram. The second medium is photo-refractive polymer for re-writable holograms. © 2009 Optical Society of America.
• Dongyel, K., Clarkson, E., & Milster, T. D. (2009). Effect of optical aberration on Gaussian laser speckle. Optics Express, 17(5), 3084-3100.
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  PMID: 19259145;Abstract: Optical aberration effects up to the second moment of Gaussian laser speckle are theoretically investigated for both partially and fully developed speckle. In the development, a plane-wave illuminated diffuser generates a phase-perturbed random field in the object plane that creates speckle in the image plane. Theoretical derivations show that image field statistics are generally non-circular Gaussian due to aberrations. Speckle statistics are not affected by odd-functional aberrations, such as coma, and dependency of aberrations is asymptotically ignorable for very weak or strong diffusers. Furthermore, Gaussian speckle contrast as a functional of optical aberrations exhibits a stationary point for the aberration free condition, where apparently contrast does not achieve a local maximum. Calculations of speckle contrast for several aberration conditions are also presented. © 2009 Optical Society of America.
• Hong, S., Yeo, J., Milster, T. D., & Kim, J. (2009). Study on the scanning system for deep focused beam by axicon. 2009 Optical Data Storage Topical Meeting, ODS 2009, 93-94.
• Kang, D., & Milster, T. D. (2009). Effect of fractal rough-surface Hurst exponent on speckle in imaging systems. Optics Letters, 34(20), 3247-3249.
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  PMID: 19838288;Abstract: Speckle image contrasts from a fractal rough-surface object are investigated in simulation, where the image surface is conjugate to the object surface. It is observed that the Hurst exponent H of fractal roughness affects speckle contrast and statistics dramatically. For example, a strong rough surface (σh > λ) exhibits Rayleigh statistics over increasing ranges of point spread function widths as H decreases. Conceptual explanations are also presented for effects of H and the coherence factor on speckle in imaging systems. © 2009 Optical Society of America.
• Kang, D., & Milster, T. D. (2009). Effect of optical aberration on Gaussian speckle in a partially coherent imaging system. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 26(12), 2577-2585.
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  PMID: 19956327;Abstract: Optical aberration effects on Gaussian speckle contrast are theoretically examined in an imaging system exhibiting partial spatial coherence. Analysis includes phase-perturbed random fields from a rough object illuminated by an extended source that generate speckle in the image plane. Results indicate that, unlike coherent illumination, speckle contrast in this partially coherent system depends on odd-functional aberrations, such as coma. In addition, calculations show that speckle contrast reduction as a function of coherence factor exhibits a stronger dependence on aberrations than for an aberration-free case. © 2009 Optical Society of America.
• Kang, D., & Milster, T. D. (2009). Simulation method for non-Gaussian speckle in a partially coherent system. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 26(9), 1954-1960.
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  PMID: 19721679;Abstract: Non-Gaussian speckle contrast from a phase-perturbed random object field in a spatially partially coherent system is simulated. A quasi-monochromatic extended incoherent source is modeled as a collection of independent point sources distributed on a regular grid. The source illuminates a phase screen object in a Kohler configuration. Speckle is calculated from the incoherent sum of irradiances in the image plane generated from the point sources. Simulated speckle contrasts are verified by an experiment with a fractallike rough surface distribution that is fabricated using a grayscale maskless lithography tool. Characteristics of the simulation method and physical quantities affecting speckle contrast are discussed. © 2009 Optical Society of America.
• Kim, Y., Zhang, J., & Milster, T. D. (2009). GaP solid immersion lens based on diffraction. Japanese Journal of Applied Physics, 48(3 PART 2).
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  Abstract: A hybrid solid immersion lens system (SIL) is described, in which a spherical glass cap lens, a micro gallium phosphide (micro-GaP) SIL and a diffractive optical element (DOE) are combined. Fabrication and aberration correction mechanisms are discussed. © 2009 The Japan Society of Applied Physics.
• Milster, T., Kang, D., & Milster, T. D. (2009). Effect of fractal rough-surface Hurst exponent on speckle in imaging systems. Optics letters, 34(20).
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  Speckle image contrasts from a fractal rough-surface object are investigated in simulation, where the image surface is conjugate to the object surface. It is observed that the Hurst exponent H of fractal roughness affects speckle contrast and statistics dramatically. For example, a strong rough surface (sigma(h)>lambda) exhibits Rayleigh statistics over increasing ranges of point spread function widths as H decreases. Conceptual explanations are also presented for effects of H and the coherence factor on speckle in imaging systems.
• Milster, T., Kang, D., & Milster, T. D. (2009). Effect of optical aberration on Gaussian speckle in a partially coherent imaging system. Journal of the Optical Society of America. A, Optics, image science, and vision, 26(12).
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  Optical aberration effects on Gaussian speckle contrast are theoretically examined in an imaging system exhibiting partial spatial coherence. Analysis includes phase-perturbed random fields from a rough object illuminated by an extended source that generate speckle in the image plane. Results indicate that, unlike coherent illumination, speckle contrast in this partially coherent system depends on odd-functional aberrations, such as coma. In addition, calculations show that speckle contrast reduction as a function of coherence factor exhibits a stronger dependence on aberrations than for an aberration-free case.
• Milster, T., Kang, D., & Milster, T. D. (2009). Simulation method for non-Gaussian speckle in a partially coherent system. Journal of the Optical Society of America. A, Optics, image science, and vision, 26(9).
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  Non-Gaussian speckle contrast from a phase-perturbed random object field in a spatially partially coherent system is simulated. A quasi-monochromatic extended incoherent source is modeled as a collection of independent point sources distributed on a regular grid. The source illuminates a phase screen object in a Kohler configuration. Speckle is calculated from the incoherent sum of irradiances in the image plane generated from the point sources. Simulated speckle contrasts are verified by an experiment with a fractallike rough surface distribution that is fabricated using a grayscale maskless lithography tool. Characteristics of the simulation method and physical quantities affecting speckle contrast are discussed.
• Milster, T., Kang, D., Clarkson, E., & Milster, T. D. (2009). Effect of optical aberration on Gaussian laser speckle. Optics express, 17(5).
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  Optical aberration effects up to the second moment of Gaussian laser speckle are theoretically investigated for both partially and fully developed speckle. In the development, a plane-wave illuminated diffuser generates a phase-perturbed random field in the object plane that creates speckle in the image plane. Theoretical derivations show that image field statistics are generally non-circular Gaussian due to aberrations. Speckle statistics are not affected by odd-functional aberrations, such as coma, and dependency of aberrations is asymptotically ignorable for very weak or strong diffusers. Furthermore, Gaussian speckle contrast as a functional of optical aberrations exhibits a stationary point for the aberration free condition, where apparently contrast does not achieve a local maximum. Calculations of speckle contrast for several aberration conditions are also presented.
• Yang, S., & Milster, T. (2009). Sub-surface imaging system for blue ray disk. 2009 Optical Data Storage Topical Meeting, ODS 2009, 22-24.
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  Abstract: Sub-surface imaging system using a solid immersion lens (SIL) is introduced. Aberration caused by cover layer of Blue ray disk is minimized with truncated SIL and diffractive optical element (DOE). Sub-surface imaging simulation is achieved by using rigorous coupled wave technique, partial coherence and vector diffraction. © 2009 IEEE.
• Yeo, J., Kim, M., Choi, N., Choi, S., Milster, T. D., & Kim, J. (2009). Pupil plane characteristics and filtering for optical data storage using circular polarization with a solid immersion lens. Japanese Journal of Applied Physics, 48(3 PART 2).
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  Abstract: Solid immersion lens (SIL) system is an excellent candidate for future technology to increase the data density of optical data storage. In a SIL system, properties of reflected light seen at the exit pupil strictly depend on the air gap thickness between the SIL and the top surface of the medium. Moreover, signal level and contrast reflected from the data bit is directly related to the modulation of δn=n0. In this case, the signal contrast can be improved by using an appropriate filter. However, unlike the incident beam of a linear polarized light, circular polarized light requires deeper understanding of the pupil plane characteristics corresponding to the vectorial nature of light. © 2009 The Japan Society of Applied Physics.
• Zhang, J., Kim, Y., Kim, Y., Valencia, R., Milster, T. D., & Dozer, D. (2009). High resolution semiconductor inspection by using solid immersion lenses. Japanese Journal of Applied Physics, 48(3 PART 2).
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  Abstract: A near-field subsurface (100 μm) microscope with numerical aperture (NA) = 2:45 is developed for integrated circuit (IC) inspection by using silicon solid immersion lenses (SIL). It is optimized for imaging patterns underneath the surface (around 100 μm deep). With the illumination light at 1.2 μm, a lateral resolution of better than 300nm is experimentally demonstrated. Gap control and tilt servos are suggested for the possibility of dynamic imaging. © 2009 The Japan Society of Applied Physics.
• Choi, T., Muster, T. D., Felix, D., Bletscher, W., & Hansen, D. (2008). Optical data destruction system: Device design and test results. Proceedings of SPIE - The International Society for Optical Engineering, 6879.
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  Abstract: An optical data destruction system using a high power laser beam is introduced. The system exposes data marks on optical media to a focused high power line beam. The exposure changes the physical and optical properties of the data marks and surrounding layers, making retrieval of the data impossible. Maintaining the focused laser beam on a data layer is achieved by a focus servo using a diffractive optical element (DOE). The system performance is evaluated from a number of destruction experiments on CD-Recordable (CD-R) and CD-Re Writable (CD-RW).
• Fukutake, N., & Muster, T. D. (2008). Erratum: Proposal of three-dimensional phase contrast holographic microscopy (Optics Express (2007) 15 (12662)). Optics Express, 16(8), 5964-.
• Lang, M., Aspnes, E., & Milster, T. D. (2008). Geometrical analysis of third-order aberrations for a solid immersion lens. Optics Express, 16(24), 20008-20028.
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  PMID: 19030087;Abstract: This paper gives a treatment for finding 3rd order aberrations in solid-immersion lenses (SILs) using spherical-aberration as the basis for a polynomial power expansion of the wavefront. Unlike previous work, the treatment is general for any incident and lens media, for any lens thickness, and for any chief-ray specification. Using this treatment, a tolerance analysis is given with emphasis on thickness tolerance and limitations on field of view. Major findings include tight thickness tolerance for high-index hyperhemispheres and a tolerance window for hemispheres centered about a thickness less than the radius of curvature of the lens. © 2008 Optical Society of America.
• Milster, T., Lang, M., Aspnes, E., & Milster, T. D. (2008). Geometrical analysis of third-order aberrations for a solid immersion lens. Optics express, 16(24).
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  This paper gives a treatment for finding 3rd order aberrations in solid-immersion lenses (SIL) using spherical-aberration as the basis for a polynomial power expansion of the wavefront. Unlike previous work, the treatment is general for any incident and lens media, for any lens thickness, and any chief-ray specification. Using this treatment, a tolerance analysis is given with particular discussion on thickness tolerance and limitations on field of view. Major findings include very tight thickness tolerance for high-index hyperhemisphere SILs and a thickness tolerance window for hemispheres skewed to values less than the radius of curvature of the lens.
• Chen, T., & Muster, T. D. (2007). Properties of induced polarization evanescent reflection with a solid immersion lens (SIL). Optics Express, 15(3), 1191-1204.
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  PMID: 19532348;Abstract: Properties of the induced polarization signal with a solid immersion lens (SIL) are investigated by experiments and simulations. A LaSFN9 SIL (NA=1.5) is used in the experiment. Physics of the induced polarization signal are described for several configurations of optical systems and substrates. Induced polarization signals from evanescent-wave coupling to dielectric, semiconductor and metal substrates are studied in detail. It is shown that surface plasmon waves are excited with Au substrates and the induced polarization signal is affected by the surface plasmon waves. Simulation results of the induced polarization signal for a gallium phosphide SIL (NA=2.64) are discussed. © 2007 Optical Society of America.
• Chen, T., Milster, T. D., Yang, S., & Hansen, D. (2007). Evanescent imaging with induced polarization by using a solid immersion lens. Optics Letters, 32(2), 124-126.
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  PMID: 17186038;Abstract: Image contrast enhancement, high lateral resolution, and height information are obtained with induced polarization evanescent imaging using a solid immersion lens. Experiments are conducted by imaging features on a patterned Si substrate. Imaging theory is used to predict optimum orientation of high-spatial-frequency samples, and a topographical image is derived from the induced polarization image through a calibration procedure. A numerical aperture of 1.5 is used in the experiment. Height accuracy of ±2 nm is demonstrated with a known sample. © 2006 Optical Society of America.
• Choi, N., Shim, S., Milster, T. D., & Kim, J. (2007). Optical design for the optimum solid immersion lens with high numerical aperture and large tolerance. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 46(6 B), 3724-3728.
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  Abstract: Super hemispherical solid immersion lens system becomes a matter of interest due to its high numerical aperture (NA) gain. However, because of the instability of the aplanatic condition, even small amount of alignment error can easily lower the optical performance. To overcome the instability while maintaining high NA gain, we suggest an optimum solid immersion lens (opti-SIL) system which combines the advantages of both super hemispherical SIL (hyper-SIL) and hemispherical SIL (hemi-SIL). Exemplary designs and simulation results of the tolerance analysis show that opti-SIL system has much higher tolerances to various performance-lowering factors than hyper-SIL, even with relatively small NA resignation. © 2007 The Japan Society of Applied Physics.
• Fukutake, N., & Muster, T. D. (2007). Proposal of three-dimensional phase contrast holographic microscopy. Optics Express, 15(20), 12662-12679.
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  PMID: 19550534;Abstract: We propose a three-dimensional phase contrast digital holographic microscopy. The object to be observed is a low-contrast transparent refractive index distribution sample, such as biological tissue. Low contrast phase objects are converted to high contrast images through the microscopy we propose. In order to gain high three-dimensional resolution, the direction of pump plane wave is scanned, and separate holographic images produced at each angle are acquired and decoded into complex amplitude in Fourier space. The three-dimensional image is reconstructed in a computer from all information acquired through the system. The resolution in the direction of the optical axis is increased by utilizing a Aπ configuration of objective lenzes. © 2007 Optical Society of America.
• Lang, M., & Milster, T. D. (2007). Investigation of optics in the 10-200μm size regime. Optical Review, 14(4), 189-193.
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  Abstract: Optical components and systems with dimensions between 10 and 200 mm are discussed with specific examples of testing, simulation, and assembly methods. This size regime, which is conventionally classified with micro-optics, offers attractive possibilities for next-generation micro-optics packaging. However, optics in this regime suffer from few available testing and simulation tools. Several theoretical application examples are described, including a high-index solid immersion lens and a pickup for optical data storage. Challenges and solutions for design and simulation, testing, and assembly of such systems are also discussed. © 2007 The Optical Society of Japan.
• Lang, M., Milster, T. D., Minamitani, T., & Borek, G. (2007). Investigation of micro solid immersion lens mounting systems. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 46(6 B), 3737-3740.
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  Abstract: Concept, design and analysis of several solid immersion lens (SIL) mounting systems utilizing high-index refractive micro SILs are described. This paper proposes several designs for wafer-scale SIL assemblies capable of a numerical aperture of 2.2. © 2007 The Japan Society of Applied Physics.
• Milster, T. (2007). Hands-on workshop for computer-generated holography. Optics and Photonics News, 18(11), 18-19.
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  Abstract: The University of Arizona's College of Optical Sciences held a three-day workshop to teach participants the design and fabrication of computer-generated holography (CGH) and Diffractive optical elements (DOE) using a custom maskless lithography tool. The maskless lithography tool is used by students to fabricate various DOEs and CHGs in photoresists and chrome masks. The students designed DOE to measure the focal length variation of the refractive lens and the DOE using red and green lasers. The students at the workshop also experimented with a CGH simulation program that incorporated 3-D properties of image reconstruction. The participating students and faculty applied the testing experience to evaluate aspheres for satellite applications.
• Milster, T. D. (2007). Data Storage, Optical. The Optics Encyclopedia. doi:10.1002/9783527600441.OE011
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  In its most general definition, optical data storage is simply using light as a tool to store and retrieve data. Optical data storage is found in popular consumer products. Compact Discs (CDs), Digital Versatile Discs (DVDs), and MiniDiscs (MDs), are all forms of optical data storage. More advanced forms of optical data storage include high-speed devices and library products. All optical data storage devices use optical principles to achieve high data density, rugged packaging, reliable information retrieval, and cost-effective production. There are many forms of optical storage media and many types of optical systems used to scan data. This chapter discusses the basic principles of optical data storage, types of commercial optical media available in 2003, several performance parameters, and some interesting prospects for future systems. Keywords: optical data storage; optical recording; compact disks; digital versatile disks; optical disks; optical memory; optical servos
• Won, K., Choi, N., Lee, J., Shin, Y., Lee, K., Milster, T. D., Lee, J., & Kim, J. (2007). Advanced SIL system with high NA and large tolerance. Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest.
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  Abstract: To achieve high NA and large tolerance, we designed a new SIL system (Optimum SIL) which combines each advantages of the Hyper SIL and the Hemi SIL system. Also using micro-SEL system we can improve its performance. There are simulation results which support our works.
• Zhang, J., Lang, M., Milster, T. D., Chen, T., Aspnes, E., & Bell, B. (2007). Fabrication and testing of a GaP SIL with NA = 2.64. Proceedings of SPIE - The International Society for Optical Engineering, 6620.
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  Abstract: A solid immersion lens (SIL) is described with NA = 2.64 that is fabricated from a two-step process using a large BK7 glass hemisphere and a small GaP hemisphere. The Gallium Phosphide (GaP) hemisphere has a radius 114μm, and is cemented in the center of BK7 SIL with index-matching epoxy. The BK7 SIL thickness is accommodated to have both BK7 SIL and GaP SIL in an image centric configuration. The two-step GaP SIL is tested on an induced polarization imaging system. Induced polarization pupil images, the native polarization image and induced polarization image of a DVD RW sample are given in this paper.
• Chen, T., & Milster, T. D. (2006). Near-field induced polarization imaging for optical data storage metrology. 2006 Optical Data Storage Topical Meeting - Post Deadline Papers, 37-39.
• Chen, T., & Muster, T. D. (2006). Near-field induced polarization imaging for optical data storage metrology. Proceedings of SPIE - The International Society for Optical Engineering, 6282.
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  Abstract: Near-field induced polarization imaging with a solid immersion lens (SIL) is used to provide high lateral resolution compared with conventional far-field microscopy. In addition, a new technique is used to obtain height information from the near-field induced polarization (cross polarized) image. Several optical data storage samples, including DVD-R, DVD-RW, BD-RW, are studied with this imaging technique. A calibration target indicates an accuracy of ± 2nm for obtaining height information.
• Chen, T., Milster, T. D., & Yang, S. (2006). Experimental investigation of photomask with near-field polarization imaging. Proceedings of SPIE - The International Society for Optical Engineering, 6349 I.
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  Abstract: Near-field induced polarization imaging with a solid immersion lens (SIL) is used to provide high lateral resolution for both native and induced polarization (cross polarized) images. A new technique is used to obtain height information from the near-field induced polarization image. An AltPSM mask sample is studied with this imaging technique, and compared to imaging with an AFM and a PSI interferometer. Topological data from the near-field induced polarization image are within a few nanometer of the AFM result, without contacting surface. In addition, features due to undercutting the Cr are observable in the induced polarization image.
• Chen, T., Milster, T., Park, S., McCarthy, B., Sarid, D., Poweleit, C., & Menendez, J. (2006). Near-field solid immersion lens microscope with advanced compact mechanical design. Optical Engineering, 45(10).
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  Abstract: A compact mechanical package is developed for a standard microscope that implements a solid immersion lens (SIL) on a retractable bimorph swing arm. With the compact package mounted on an inverted microscope, far-field and near-field images are obtained at the same location by moving the SIL with the swing arm. With white-light incoherent illuminafion, the resolution of this system for observing digital versatile discs is around 200 nm with an effective numerical aperture of 1.5. Imaging with the SIL is compared with an atomic force microscopy scan. © 2006 Society of Photo-Optical Instrumentation Engineers.
• Choi, T., & Milster, T. D. (2006). Change in data marks and groove structures of compact recordable disks in response to a high power laser beam. Optical Engineering, 45(6).
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  Abstract: Changes in data marks and groove structures are examined when a high power laser beam (>0.5 W) is focused on compact disk recordable (CD-R) data layers. Observations are recorded as a function of exposure condition and the type of dye used in the recording layer. All samples experience a decrease in the depths of data mark features and the pregroove modulations on exposure. Data marks on cyanine- and azo-dye disks become optically invisible after exposure, while data marks on phthalocyanine-dye disks remain visible, even after high-power exposure. Also, phthalocyanine-dye disks show interesting phenomena, including mixture of the dye and the substrate material during recording and contrast reversal of the marks. © 2006 Society of Photo-Optical Instrumentation Engineers.
• Dvornikov, A. S., Milster, T. D., Walker, E., & Rentzepis, P. M. (2006). Two-photon 3D high-density optical storage media: Optical properties, temperature, radiation, and fatigue studies. Proceedings of SPIE - The International Society for Optical Engineering, 6308.
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  Abstract: We have employed new molecular media for volumetric data storage by means of two photon absorption. The optical and spectroscopic characteristics of the materials that are relevant to volumetric optical storage are described. In addition, fatigue characteristics of the photochromic media and substrates used in the fabrication of the storage devices are presented. These include temperature, read/write/erase cycles and space environments such as heavy ion and proton radiation, and heat under vacuum.
• Milster, T. D., & Zhang, Y. (2006). Materials for multilayer recording. MRS Bulletin, 31(4), 318-323.
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  Abstract: An attractive feature of optical discs is their capacity. Recent research has indicated that the capacity of optical discs can be increased by using multiple layers of bitwise data. Layers are spaced along the depth dimension of the discs. Individual layers are recorded and information is retrieved in a manner that is very similar to conventional optical disc systems using a single layer. The data capacity of each layer is nearly equal to the capacity of a single layer, thus increasing the capacity of a disc by a factor equal to the number of layers. In fact, dual-layer optical discs are already commercially available. With some storage materials, it is possible to record hundreds of data layers. However, system engineering trade-offs, like readout speed, are of concern. More conventional materials can also be used for multilayer recording, but the number of layers is limited by the transmission properties of each layer. This article reviews the materials systems for multilayer recording, the interplay between materials properties and performance, and the optical systems used for multilayer recording.
• Milster, T. D., Park, S. K., & Zhang, Y. (2006). Prospects and limitations for large numbers of multi-layers in optical data storage. 2006 Optical Data Storage Topical Meeting - Post Deadline Papers, 179-181.
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  Abstract: Fourth-generation technologies that use multiple layers are now under investigation. This presentation describes the inter-layer interference and crosstalk characteristics of multiple layers under several illumination conditions using Babinet decomposition of the recording structure. Limitations based on performance bounds are introduced for various film characteristics, like reflectivity, transmission and layer spacing. Primary results include that the total crosstalk is minimized for certain layer spacings for both coherent and incoherent illuminations. The incoherent illumination shows lower values of total crosstalk and more generous tolerances than the coherent illumination. © 2006 IEEE.
• Park, S., Milster, T. D., & Zhang, Y. (2006). Prospects and limitations for large numbers of multi-layers in optical data storage. Proceedings of SPIE - The International Society for Optical Engineering, 6282.
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  Abstract: Media considerations for a multiple-layered system using conventional thin films are presented in detail. The media are designed and fabricated for various geometries of thin film coatings to satisfy the optimum media condition minimizing inter-layer crosstalk for conventional reflective volumetric optical data storage systems.
• Beaudry, N. A., & Milster, T. D. (2005). Imaging properties of a patterned rough surface: Effects of defocus. Optical Engineering, 44(6), 1-10.
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  Abstract: A theoretical investigation of the effects of imaging a patterned rough surface through focus is performed, and the statistics of the image plane irradiance, as well as those of the image pattern printed in a threshold-type photoresist, are investigated. It is demonstrated that the line edge roughness in the printed image increases substantially as the image plane is moved out of focus, for both fully and partially coherent optical systems. Furthermore, the increase in line edge roughness occurs in what is considered to be an otherwise acceptable depth of focus for an ideal system. © 2005 Society of Photo-Optical Instrumentation Engineers.
• Beaudry, N. A., & Milster, T. D. (2005). Imaging properties of a patterned rough surface: Effects of roughness correlation and partial coherence. Optical Engineering, 44(7), 1-8.
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  Abstract: An investigation of partially coherent speckle is performed, including the effects of a pattern structure in the object plane of an imaging system. It is demonstrated that, when forming an image of a patterned rough surface into a binary photoresist, the width variations produced in the resultant pattern (also called line edge roughness) can increase as the imaging system becomes more incoherent. This unusual behavior occurs because of an interaction between the speckle produced by a rough surface and the partially coherent imaging properties of the pattern structure. It is shown that the increase in line edge roughness for a more incoherent system requires that the surface roughness of the object structure have a correlation length that is substantially smaller than the resolution of the imaging system. © 2005 Society of Photo-Optical Instrumentation Engineers.
• Chen, T., Milster, T., Nam, D., & Yang, S. H. (2005). Experimental investigation of solid immersion lens lithography. Proceedings of SPIE - The International Society for Optical Engineering, 5754(PART 1), 254-261.
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  Abstract: There are several next generation technologies for high resolution lithography, such as ArF wet immersion, F2, EUV, etc. However, these technologies are very expensive because of projection lens and mask costs. Near-field optics using a solid immersion lens (SIL) can meet the requirement of high resolution in a cost-effective way. In this paper, a very compact and inexpensive high resolution system using a SIL is introduced and preliminary experimental results are presented using a 405nm laser diode system. The SIL is used with a modified conventional inverted microscope. The air gap between the SIL flat bottom surface and the wafer is kept less than 50nm. Optical reflected power from SIL bottom and wafer interface is used to control the gap. A high resolution experiment with 405nm wavelength is discussed.
• Chen, T., Muster, T., & Yang, S. H. (2005). Semiconductor pattern analysis with induced polarization. Proceedings of SPIE - The International Society for Optical Engineering, 5992(1).
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  Abstract: Image contrast enhancement, resolution improvement and accurate height information are obtained by near-field induced polarization imaging using a solid immersion lens (SIL) microscopy. A semiconductor PC processor is investigated by this imaging technology. With 520nm linear polarization illumination, around 100nm feature size is resolvable, and topographical information is also achieved from this induced polarization image. We demonstrate this near-field induced polarization imaging is a fast acquisition, large field and high resolution metrology solution.
• Choi, T., Milster, T. D., & Lang, M. (2005). Wavelength-domain tracking in multiple-beam optical storage systems. Optical Engineering, 44(5), 1-9.
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  Abstract: Wavelength-domain tracking (WDT) is a new concept for application in multiple-beam optical storage systems. Tracking errors caused by use of multiple beams on curved tracks are avoided in WDT systems by optimizing separations of focused beam spots. The control of beam spot separations is accomplished by wavelength tuning of individual laser sources. Feasibility of WDT is demonstrated by implementation and testing of a single-beam WDT tracking servo. Also, a novel method of error signal extraction by low-frequency modulation is proposed. © 2005 Society of Photo-Optical Instrumentation Engineers.
• Lang, M., Milster, T. D., Minamitani, T., Borek, G., & Brown, D. (2005). Fabrication and characterization of sub-100 μm diameter gallium phosphide solid immersion lens arrays. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 44(5 B), 3385-3387.
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  Abstract: Fabrication and testing of a sub-100 μm gallium phosphide solid immersion lens is described with suitable sphericity (
• Milster, T. D. (2005). Horizons for optical data storage. Optics and Photonics News, 16(3), 28-33.
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  Abstract: The recent developments in the optical data storage technology are studied. CDs and DVDs are well established in the marketplace and Blu-ray Disc (BD)-type products that will be used for high-definition television (HDTV) and home theater, are now becoming available. Magnetically amplifying magneto-optical system (MAMMOS) technology may be used for future optical discs. The outlook for optical storage technology is clearly encouraging and provides a strong motivation for advanced research.
• Nam, D., Milster, T. D., & Chen, T. (2005). Potential of solid immersion lithography using I-line and KrF light source. Proceedings of SPIE - The International Society for Optical Engineering, 5754(PART 2), 1049-1056.
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  Abstract: ArF technology is currently being used for 80nm resolution in the photo-lithography field, and ArF wet immersion technology is expected to be used for high resolution systems down to 50nm. Between ArF wet immersion technology and EUV technology, there is no proper technology that can cover the resolution range from 50nm to 30nm. In this paper, a new lithography technology using a Solid Immersion Lens (SIL) is introduced as an idea for very high resolution, and its resolution achievement is estimated through simulation. SIL technology is a near-field optics technology that achieves high resolution. A SIL is a hemispherical lens, and the incident beam is normal with respect to the surface of the lens. Because a high refractive index material is used for the SIL, very high numerical aperture provides high resolution. The resolution limit is estimated by calculating the vector irradiance inside the thin-film stack composed of the SIL, air gap, photoresist, anti-reflection layer and substrate. Feature size is estimated over reasonable exposure latitude at 20nm depth in the resist. Results show that, using a 365nm wavelength source, 70nm resolution is expected, and 50nm resolution is expected with a 248nm wavelength source. With a shorter wavelength light source and a proper SIL material of high refractive index for the wavelength, higher resolution can be achieved.
• Park, S., Milster, T. D., Miller, T. M., Butz, J., & Bletscher, W. (2005). Master and slave beam servo technique for volumetric bit-wise optical data storage. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 44(5 B), 3442-3444.
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  Abstract: A master and slave servo technique that maintains tracking and focus registration inside a volumetric disk is presented, and the misregistration of the slave beam with respect to the master beam due to disk tilt and beam skew is calculated. © 2005 The Japan Society of Applied Physics.
• Chen, T., Felix, D., Park, S., Hauser, P., McCarthy, B., Sarid, D., Poweleit, C., Menendez, J., & Milster, T. (2004). Near-field solid immersion lens (SIL) microscope with advanced compact mechanical design. Proceedings of SPIE - The International Society for Optical Engineering, 5380, 634-641.
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  Abstract: A compact mechanical package is developed for a standard microscope that implements a solid immersion lens (SIL) on a retractable bimorph swing arm. With the compact package mounted on an inverted microscope, far-field and near-field images are obtained at the same location by moving the SIL in place with the swing arm. With white-light incoherent illumination, the resolution of this system for observing digital versatile discs (DVDs) is around 200nm with an effective NA of 1.5. Imaging with the SIL is compared to an atomic force microscopy (AFM) scan.
• Choi, T., Milster, T. D., & Lang, M. (2004). Wavelength-domain tracking in multiple-beam optical storage systems. Proceedings of SPIE - The International Society for Optical Engineering, 5380, 197-208.
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  Abstract: Wavelength-domain tracking is a new concept for application in multiple-beam optical storage systems. Tracking errors caused by use of multiple beams on curved tracks are avoided in WDT systems by optimizing separations of focused beam spots. The control of beam spot separations is accomplished by wavelength tuning of individual laser sources. Feasibility of WDT is demonstrated by implementation and testing of a single-beam WDT tracking servo. Also, a novel method of error signal extraction by low-frequency modulation is proposed.
• Kasanavesi, S. K., Milster, T. D., Felix, D., & Choi, T. (2004). Data recovery from a compact disc fragment. Proceedings of SPIE - The International Society for Optical Engineering, 5380, 116-127.
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  Abstract: We propose a three-step modular approach to recover data from Compact Disc (CD) fragments. The basic idea is to simulate the effect of an optical read-write system. A high power microscope is used to capture a series of contiguous image frames and recover a derived electronic signal, which is similar to the actual signal that is detected in conventional systems. Real data bytes are recovered from this derived electronic signal using signal processing techniques. Finally, data descrambling is performed to determine the user sequence of these recovered real data bytes. The procedure to recover the Absolute Time In Pre-groove (ATIP) information from the real data bytes is also presented. Statistical analysis of the probability of recovering ATIP information from a CD is illustrated using experimental data. A benchmark is provided for the minimum CD track length that is required to partially or completely recover the ATIP information.
• Khoh, A., Samudra, G. S., Yihong, W. u., Milster, T., & Choi, B. (2004). Image formation by use of the geometrical theory of diffraction. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 21(6), 959-967.
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  PMID: 15191175;Abstract: A deeper understanding of imaging behavior is needed with the widespread adoption of optical proximity correction in advanced lithography processes. To gain insight into the printing behavior of different mask pattern configurations, we derive edge-based and vertex-based image models by combining concepts contained in the geometrical theory of diffraction and Hopkins's image model. The models are scalar models and apply to planar, perfectly conducting mask objects. © 2004 Optical Society of America.
• Milster, T., Chen, T., Nam, D., & Schlesinger, E. (2004). Maskless lithography with solid immersion lens nano probes. Proceedings of SPIE - The International Society for Optical Engineering, 5567(PART 1), 545-556.
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  Abstract: The International Technology Roadmap for Semiconductors (ITRS) shows that 45 nm and lower feature sizes are required in lithographic production before the year 2007. Both immersion lithography and EUV lithography can play major roles in realizing this goal. However, a maskless lithography system capable of producing 45 nm features is an attractive option for small-volume semiconductor fabrication, such as with ASIC manufactures. Compared with a conventional lithography system, the maskless feature of the system allows the chip designer to be free of the very expensive process of mask fabrication and to shortcut development time. In this paper, we discuss a new maskless lithography concept employing an array of solid immersion lens (SIL) nano-probes. The nano-probes are efficient near-field transducers. Each transducer is the combination a SIL, a dielectric probe tip and an antenna structure. The nano-probes are fabricated in arrays that dramatically improve throughput. By combining these technologies, it should be possible to fabricate an efficient array of near-field transducers with optical spot dimensions of around 20 nm when illuminated by a 405 nm laser diode source. This paper plans to address, for the first time, the efficient generation of an array of light spots with dimensions of λ/20 or less that couple efficiently into dielectric films, like photoresist.
• Olkkonen, J., Kataja, K., Aikio, J., Howe, D. G., & Milster, T. D. (2004). Analysis of sub-wavelength apertures via the extended FDTD SF technique. Proceedings of SPIE - The International Society for Optical Engineering, 5380, 653-662.
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  Abstract: We introduce a technique which enables FDTD modeling of the transmission of obliquely incident plane waves through an aperture in a film having infinite lateral extent. As an example, we analyze surface plasmon enhanced light transmission through a cylindrical aperture in a silver film.
• Wu, F., Shieh, H. D., Huang, D., & Milster, T. D. (2004). Performance of a write-once multilayer optical disk that uses transparent recording material with an optical switching layer. Applied Optics, 43(29), 5498-5502.
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  PMID: 15508607;Abstract: A volumetric optical disk that has multiple transparent films with optical switching layers is used as a recording medium to increase the number of recording layers. In the disk the optical switching layer is adapted to reduce decay of laser energy and increase reading and recording sensitivity. Well-defined marks of ∼100-nm depth can be placed precisely on the transparent films by a focused laser beam. Writing and reading of a four-layer recordable disk, fabricated by molding and spin, bonding, have been demonstrated experimentally. The volumetric disk can achieve a nigh recording capacity with conventional optical pickups. © 2004 Optical Society of America.
• Wu, F., Shieh, H. D., Milster, T. D., & Huang, D. (2004). Write-once volumetric optical disk using transparent recording material with an optical switching layer. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 43(7 B), 4937-4940.
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  Abstract: A volumetric optical disk having multiple transparent films with optical switching layers is proposed as a recordable medium to increase the number of recording layers. In the disk, an optical switching layer is adopted to reduce laser energy decay and increase recording sensitivity for reading and recording, respectively. A well-defined deformation area (mark) with submicron to nanometric dimensions can be yielded precisely on the transparent films by a focused laser beam. The peak writing power of 7mW for a four-layer recordable medium, fabricated by molding and spin bonding techniques, was demonstrated experimentally as an example. The proposed volumetric disk can achieve a higher recording capacity by using conventional optical pickup units.
• Zhang, Y., & Milster, T. D. (2004). Simulation of a fluorescent bit-wise volumetric optical data storage system. Proceedings of SPIE - The International Society for Optical Engineering, 5380, 376-386.
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  Abstract: An analytical optical transfer function concept and a quasi-vector diffraction simulation tool are introduced to simulate a fluorescent bit-wise volumetric optical data storage system. Examples and a comparison of simulation results are presented.
• Zhang, Y., Butz, J., Curtis, J., Beaudry, N., Bletscher, W. L., Erwin, K. J., Knight, D., Milster, T. D., & Walker, E. (2004). Characterization of a bit-wise volumetric storage medium for a space environment. Optics Express, 12(12), 2662-2669.
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  PMID: 19475107;Abstract: We report playback performance results of volumetric optical data storage disks that are made from a class of light-absorbing (photo-chromic) compounds. The disks are exposed to a simulated space environment with respect to temperature and radiation. To test for temperature sensitivity, a vacuum oven bakes the disks for certain amount of time at a designated temperature. Radiation exposure includes heavy ions and high energy protons. Disks fail in high temperature and large proton-dose conditions. Heavy ions do not cause significant disk failure. The prevention of disk failure due to harsh space environments is also discussed. © 2004 Optical Society of America.
• Zhang, Y., Milster, T. D., Kim, J. S., & Park, S. (2004). Advanced lens design for bit-wise volumetric optical data storage. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 43(7 B), 4929-4936.
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  Abstract: The storage capacity of a fluorescent bit-wise volumetric optical data storage system is limited by the inter-layer crosstalk and the maximum compensation range of spherical aberration induced by different layers inside the medium. Lens designs of far-field and near-field optical systems suitable for volumetric storage are presented. The maximum compensation range of each design is calculated. The storage densities of far-field and near-field confocal systems in terms of bits-in-2re derived based on the maximum compensation ranges and appropriate data layer spacings that induce a -30 dB maximum level of inter-layer crosstalk. It is shown that an optimized near-field system is able to achieve 1.65 Tb-in-2 data density.
• Zhou, L., Bain, J. A., Schlesinger, T. E., Lang, M., & Muster, T. D. (2004). Prototype mode index lens for heat assisted magnetic recording. Proceedings of SPIE - The International Society for Optical Engineering, 5380, 28-33.
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  Abstract: Mode index lenses for light delivery intended for use as part of a heat-assisted magnetic recording head were designed and tested. The waveguides in which these lenses were constructed consisted of a Si 3N 4 guiding layer on top of a SiO 2 cladding layer with thickness of 1 μm. The top confining layer of the waveguide was air. Mode index lenses were created by using Si 3N 4 regions of two different thicknesses (350 nm and 140 nm), having mode indices of 1.925 and 1.745, respectively. A scanned optical fiber was used to profile light scattered out of the waveguide. The measured spot size is 2.2 μm at the exit of the final lens in a three-lens sequence, which is an upper bound on the actual spot size with this resolution set by limitations of the measurement system.
• Khoh, A., Flagello, D., Milster, T., Choi, B., Samudra, G. S., & Yihong, W. u. (2003). Extending a GTD-based image formation technique to EUV lithography. Proceedings of SPIE - The International Society for Optical Engineering, 5037 II, 682-689.
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  Abstract: An image formation technique based on the Geometrical Theory of Diffraction was presented last conference. The technique is a scalar technique and is applicable to infinitely thin and perfectly conducting mask. We explore in this paper the extension of the technique to 1D Extreme Ultra-Violet(EUV) Lithography mask, taking into consideration both the material property and the topography of the mask. Vectorial nature of light is incorporated in the treatment. Results obtained are promising and encouraging. Computation time is relatively much shorter and the technique could simulate irradiance profile for any illumination angle. The technique is simple and elegant and lends understanding to image formation. We conclude that the asymmetry-through-focus characteristic usually found in EUV and Phase Mask imaging is an imaging phenomenon. We also conclude that corrections for proximity effect and pattern infidelity will be needed when EUV Lithography is introduced at the 32 nm node, assuming a system NA of 0.25. Lastly, for a partially coherent illumination, it appears necessary to compute the irradiance corresponding to each illumination point individually.
• Miller, T. N., Butz, J., Milster, T. D., Bletscher, W., Walker, E. P., Park, S., & Felix, D. (2003). A novel method for tracking in homogeneous volumetric media. Proceedings of SPIE - The International Society for Optical Engineering, 5069, 269-278.
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  Abstract: Volumetric media have great potential for meeting future optical data storage demands, but homogeneous media lack internal features for tracking. A novel method of tracking inside homogeneous media is described that uses external reference tracks attached to the media. Several possible configurations for implementing the "slave-servo" concept are described and compared. An optical design for the most promising configuration is presented. This design utilizes a diffractive optical element for dispersion compensation. Modeling describes the limits of device performance and alignment. Early prototype results are presented.
• Milster, T. D. (2003). Physical Optics Simulation in Matlab for High-Performance Systems. Optical Review, 10(4), 246-250.
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  Abstract: Two advanced optical system applications are implemented in a Matlab™ based simulation engine. The applications are aligning a micro-optic fiber coupler and scanning an optical disk with a readout system having an effective numerical aperture of 1.8. Many phenomena, like scalar diffraction, vector diffraction, addition of aberrations, thin-film interactions, and Babinet decomposition are described in the examples. A powerful graphical user interface (GUI) is also described that allows users to define optical elements, program operations and control program flow. Users can also easily interface custom field operations to the simulation engine.
• Milster, T. D., & Tang, S. G. (2003). Generation of compact near-field energy for optical recording: Transducer efficiency and signal detection. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 42(2 B), 1095-1100.
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  Abstract: A new theory of illumination is derived for near-field optical transducers, in which transmitted power is related to total power in the illuminating laser beam. Several transducers are compared, including simple holes in metallic films, a dielectric probe and solid immersion lens combination, and plasmon-enhanced holes. The ratio of transmitted power to incident power is a function of the illumination numerical aperture, due to the angular selectivity of the transducers. Also, a simplified collection theory is reviewed, which reveals that, when transducers are used for the collection of data signals in optical storage applications, a combination of the transducer and a solid immersion lens provides a large angular collection range, and hence a good contrast signal.
• Tang, S., & Milster, T. D. (2003). Consideration and control of writing conditions with near-field aperture solid immersion lens probe. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 42(2 B), 1090-1094.
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  Abstract: Control of writing conditions for near-field aperture-SIL (APSIL) probe is investigated with respect to polarization, axial focus position of the objective lens and beam transverse misalignment. Both FDTD simulations and edge-scan experiments are used in the investigation. The TE direction is the optimal writing polarization direction and the probe exit plane is the optimum focus position of the illuminating lens. Spot size change and spot position shift relative to the center of the probe are observed with TE polarization when the writing beam is transversely misaligned.
• Tien, C., Chou, H., Chiu, Y., Hsu, W., Milster, T. D., Lai, Y., & Shieh, H. D. (2003). Fiber-lens-based module for optical recording applications. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 42(7 A), 4345-4348.
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  Abstract: An optical fiber-lens-type pickup with numerical aperture (NA) ≅ 0.27 was demonstrated for thermal recording of continuous 1.6-μm-wide lines on MO disks with 50% throughput efficiency. Moreover, a Si-micromachined near-field module integrated with a fiber lens, solid immersion lens (SIL), and submicron aperture was fabricated to improve the mechanical fragility and increase the NA of the optical-fiber-based pickup. The preliminary configuration design and measurement suggest the feasibility of the module as a submicron heat source for high-density optical data storage.
• Zhang, Y., Butz, J., Curtis, J., Beaudry, N., Bletscher, W. L., Erwin, K. J., Knight, D., Milster, T. D., & Walker, E. (2003). Characterization of a photochromic bit-wise volumetric storage media for space applications. Proceedings of SPIE - The International Society for Optical Engineering, 5069, 286-293.
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  Abstract: We report playback performance results of volumetric optical data storage disks that are made from a new class of light-absorbing (photo-chromic) compounds. The disks are first exposed to a simulated space environment. In order to simulate the space environment, a vacuum oven bakes the disks for certain amount of time at a designated temperature. Test results in this temperature study are fit into an Arrhenius model. Disks are also exposed to radiation doses similar to those found in a space environment. Disks fail in high temperature and large proton-dose conditions. Heavy ions do not cause significant disk failure. The prevention of disk failure due to harsh space environments is also discussed.
• Zhang, Y., Muster, T. D., Butz, J., & Bletcher, W. (2003). A new test stand for dynamically testing coupon samples. Proceedings of SPIE - The International Society for Optical Engineering, 5069, 357-360.
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  Abstract: A new dynamic test stand is built to test coupon samples for volumetric bit wise optical data storage applications. An unconventional rotating head and fixed sample design is employed. Results from media samples are reported that illustrate pulse-length/power optimization and focus sensitivity. One sample is shown to be appropriate for volumetric applications based in its focus sensitivity.
• Beaudry, N. A., & Milster, T. D. (2002). Interferometric phase reconstruction by nonuniform shifting of the reference beam. Applied Optics, 41(10), 1915-1921.
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  PMID: 11936790;Abstract: A method for phase measurement in common-path interferometers, believed to be novel, is presented. We use the property of phase reconstruction algorithms, such as the Carré and Hariharan algorithms, that do not require uniform phase across the reference beam. Only the ratio of the phase steps must be the same at each pixel. We show phase measurement and reconstruction in a common-path interferometer by shifting either the tilt or the focus of the reference wave front. We present a theoretical explanation of phase measurement using this property. We also present results from a proof-of-principle experiment using a scatterplate interferometer, in conjunction with the tilt phase-shifting technique, to measure the reflected phase of a test optical element. Furthermore, we present a computer simulation to demonstrate the mathematical validity of this measurement technique using defocus shifting, rather than tilt shifting, in the reference wave front. © 2002 Optical Society of America.
• Hashimoto, N., & Milster, T. D. (2002). Optical equalizer of a data storage system using liquid crystal super-resolution devices. Proceedings of SPIE - The International Society for Optical Engineering, 4342, 486-491.
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  Abstract: Super-resolution with suppressed side-lobes using a liquid crystal super-resolution device and its application to optical equalizer are presented. The liquid crystal device modulates linearly polarized input into orthogonaled linearly polarized pairs and to place the device in focusing optics causes super-resolution effects and polarization states of its side - lobes become different from its main - lobes. Then we can reduce side-lobes using polarization filterings. To apply this device to optical heads with an analyzer in the collection path, we can find variable optical equalizer effects by rotating a direction of the analyzer.
• Jo, J. S., & Milster, T. D. (2002). Tolerance issues in solid immersion lens systems. Proceedings of SPIE - The International Society for Optical Engineering, 4342, 312-319.
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  Abstract: Analysis that includes physical optics with diffraction, polarization, and aberration, as well as geometrical optics is used to understand tolerancing of SIL systems. Irradiance distributions inside a simple substrate are explored as the distance between the objective lens and SIL and the radius of curvature of the SIL are varied. Gap-induced aberration is included in the analysis. Irradiance distributions inside a phase-change recoding medium are explored as the decentration of the SIL and angular misalignment of the incident beam onto the objective lens are changed. Reflection characteristics are explored versus air gap heights and the thickness of the recording layer in a magneto-optical medium.
• Jo, J. S., Milster, T. D., & Erwin, J. K. (2002). Phase and amplitude apodization induced by focusing through an evanescent gap in a solid immersion lens microscope. Optical Engineering, 41(8), 1866-1875.
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  Abstract: We characterize phase and amplitude apodization induced when a converging beam passes through an evanescent gap. The apodization is caused by vector transmission and reflection properties. General characteristics are described for solid immersion lens indices from nSIL = 1.5 to 3.1, gap heights from h = 0 to 300 nm, and marginal ray angles αm = 0.7 or 0.84, where αm is the direction cosine of the marginal ray angle inside the solid immersion lens. A small amount of defocus is found to be a good compensator of the phase apodization for low nSIL and h. After proper defocus is applied, asymmetry of focus in the spot may remain, primarily due to the uncompensated amplitude apodization. Simplification of the phase and amplitude characteristics is accomplished by applying a Jones-matrix expansion to the transmission coefficient through the gap. Simulation and experiment quantify the effect with a simple solid immersion lens geometry. © 2002 Society of Photo-Optical Instrumentation Engineers.
• Khoh, A., Milster, T., Choi, B., Samudra, G. S., & Yihong, W. u. (2002). Influence of OPC features on the profile of 2D mask patterns. Proceedings of SPIE - The International Society for Optical Engineering, 4691 II, 1127-1138.
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  Abstract: With increasing use of OPC, there is a need to understand image formation better. The widely used Hopkin's model gives believable results but yields little insight into image formation. We present in this paper a new image formation technique based on the Geometrical Theory of Diffraction (GTD). Using GTD, we obtained a relationship between the edge on the mask and the disturbance in image space. We call this disturbance the Diffraction Edge Response (DER). Heuristically, the strength of the DER must drop nearing the end of an edge. The DER is thus modulated by a certain function. At this point of the development, we could not derive an expression for this function. However, we postulate that the Modulation Function is the square root of the intensity of the edge segment. This postulate is justified by the excellent agreement with results obtained using existing simulation tool. Image formation is thus governed by the DER and the Modulation Function. If the new image formulation is separated into the cross and non-cross terms respectively, it is observed from simulations that the cross terms have values closed to zero at the feature boundary. This unique property, stemming from the nature of the DER, turns a non-linear problem into approximately a linear problem at the feature boundary. A host of problems could then be understood. Using this tool, we show how the behavior of a simple corner varies with NA, PC and its dimension. We also discuss the implications of this tool on current OPC strategy. We have assumed an aberration-free system and an infinitely-thin 2D mask in this development. It is possible to extend it to an aberrated system and to 3D-mask. That will be our work in the future.
• Kim, J., & Milster, T. D. (2002). Design aspects of waveguide hybrid advanced MEMS(WHAM). Proceedings of SPIE - The International Society for Optical Engineering, 4342, 447-456.
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  Abstract: Three different versions of high numerical aperture (NAi =1.9) 0.3 ° field diffraction limited WHAM lens systems are designed for hi-density data storage by using over-hemi-cylinder surfaces. A prototype WHAM lens with NAi = 1.23 is also discussed. Detail of unique tolerance issue is presented.
• Milster, T., Beaudry, N. A., & Milster, T. D. (2002). Interferometric phase reconstruction by nonuniform shifting of the reference beam. Applied optics, 41(10).
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  A method for phase measurement in common-path interferometers, believed to be novel, is presented. We use the property of phase reconstruction algorithms, such as the Carré and Hariharan algorithms, that do not require uniform phase across the reference beam. Only the ratio of the phase steps must be the same at each pixel. We show phase measurement and reconstruction in a common-path interferometer by shifting either the tilt or the focus of the reference wave front. We present a theoretical explanation of phase measurement using this property. We also present results from a proof-of-principle experiment using a scatterplate interferometer, in conjunction with the tilt phase-shifting technique, to measure the reflected phase of a test optical element. Furthermore, we present a computer simulation to demonstrate the mathematical validity of this measurement technique using defocus shifting, rather than tilt shifting, in the reference wave front.
• Tien, C., Lai, Y., Milster, T. D., & Shieh, H. D. (2002). Design and fabrication of fiberlenses for optical recording applications. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 41(3 B), 1834-1837.
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  Abstract: The novel design and fabrication of a microlens on the front end of a single-mode fiber is described. The beam quality and spot size for optical recording applications are analyzed. A hyperbolic-shaped microlens on a single-mode fiber with focused spot of 1/e2 = 0.82 μm (x-direction) and 0.89 μm (y-direction) at ∼ 145 μm working distance was achieved by a simple fabrication procedure.
• Milster, T. D. (2001). Near-field optical data storage: Avenues for improved performance. Optical Engineering, 40(10), 2255-2260.
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  Abstract: Because they produce small spot size, near-field techniques are applied to optical data storage systems to increase recording density. Two practical near-field implementations are aperture probes and solid immersion lenses (SILs). The basic signal modulation characteristics of these systems are reviewed, and some considerations for improving performance are discussed. Combinations of SILs and apertures could produce data storage systems with ultra-fine resolution and good detection characteristics. © 2001 Society of Photo-Optical Instrumentation Engineers.
• Milster, T. D., & Tang, S. (2001). Highly efficient near-field probes. Optics and Photonics News, 12(12), 38-.
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  Abstract: The highly efficient near-field probes are discussed. In the near-field optical system, the object and the optical system must be closer than the wavelength of light that was used to illuminate the object. The fabrication procedure involves a photoresist exposure, development, and ion milling, with which the glass was etched into the desired probe tip array. It was found that a combination of dielectric apertures and solid immersion lens optics provide both a small spot size and high coupling efficiency.
• Milster, T. D., Akhavan, F., Bailey, M., Erwin, J. K., Felix, D. M., Hirota, K., Koester, S., Shimura, K., & Zhang, Y. (2001). Super-Resolution by Combination of a Solid Immersion Lens and an Aperture. Japanese Journal of Applied Physics, Part 2: Letters, 40(3 B), 1778-1782.
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  Abstract: A solid immersion lens is combined with various aperture shapes in order to improve resolution. Both metallic and dielectric apertures are investigated, and optimum shapes for each are determined. Fabrication techniques for each type of combination probe are discussed and implemented, and a simple experiment with a dielectric combination probe scanning a reflective grating demonstrates improved resolution compared to a solid immersion lens alone. ©2001 The Japan Society of Applied Physics.
• Milster, T. D., Felix, D., Burkhart, C. J., Butz, J., Zhang, Y., & Curtis, J. (2001). Semi-kinematic rails for construction of optical test stands. Proceedings of SPIE - The International Society for Optical Engineering, 4444, 358-361.
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  Abstract: We describe a new mounting technique for rapid alignment using semi-kinematic (SK) rails. Features of the technique include structures for positioning lens elements, beam splitters, mirrors, and the like. The SK rails are less complicated to machine than traditional v- groove technology.
• Shimura, K., & Milster, T. D. (2001). Vector diffraction analysis by discrete-dipole approximation. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 18(11), 2895-2900.
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  PMID: 11688879;Abstract: The discrete-dipole approximation is applied to vector diffraction analysis in a system with large-numerical-aperture (NA) optics and subwavelength targets. Distributions of light diffracted by subwavelength dielectric targets are calculated in a solid angle that corresponds to a NA of 0.9, and their dependence on incident polarization, target shape, and target size is studied. Electric field distributions inside the target are also shown. Basic features of the vector diffraction are clearly demonstrated. This technique facilitates understanding of the vectorial effects in systems that are expected to be applied in the future to optical data storage. © 2001 Optical Society of America.
• Tang, S., Milster, T. D., Erwin, J. K., & Bletscher, W. L. (2001). High-performance readout and recording by a combination aperture. Optics Letters, 26(24), 1987-1989.
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  PMID: 18059754;Abstract: A solid immersion lens combined with a conical dielectric tip exhibits good resolution and efficiency in reading and recording data marks on optical storage media. We demonstrate a combination aperture that produces ∼200-nm full-width 1/e2 spot size and achieves 50% optical efficiency in an edge-scan experiment. A comparison of recording with the combination aperture, with an unmodified solid immersion lens, and with a far-field system is made. © 2001 Optical Society of America.
• Upton, R. S., & Milster, T. D. (2001). Detector pattern from optical disks. Optical Engineering, 40(6), 1030-1044.
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  Abstract: The irradiance in the exit pupil of a typical optical data storage system (i.e., the detector pattern) consists of fringes formed by the interference of fields reflected from the optical disk. The reflected fields are decomposed using Babinet's principle into desired and undesired components. The behavior of the fringes depends on the interaction of the focused light spot with the features on the optical disk and media parameters, such as mark and land reflectivities, groove depth, and mark pattern. The behaviour of the desired and of the undesired fringes are determined for both write-bright media (bright data marks written on a dark background) and write-dark media (darks marks written on a bright background). Both a theoretical development and a scalar diffraction simulation tool are used in the analysis.
• Walker, E. P., & Milster, T. D. (2001). Beam shaping for a high-power vertical cavity surface emitting laser. Proceedings of SPIE - The International Society for Optical Engineering, 4443, 105-114.
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  Abstract: A high-power vertical cavity surface emitting laser (VCSEL) is described that can emit over 40 mW in pulsed operation at 780 nm. The mode structure of the device is unusual, in that only the HE31 mode lazes over a broad environment of mechanical and thermal conditions. The stable mode structure suggests that this laser may be used in an optical system like those used in optical data storage, which demand diffraction-limited performance. However, the laser mode cannot be used directly in a classical optical system due to its ring amplitude and periodic phase properties. In this paper, we discuss potential beam-shaping techniques that can be used to overcome these limitations. For example, a simple phase mask can be used to eliminate the periodic phase properties. Optical systems for focusing the shaped laser light are also discussed.
• Walker, E. P., & Milster, T. D. (2001). Beam shaping for optical data storage. Proceedings of SPIE - The International Society for Optical Engineering, 4443, 73-92.
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  Abstract: The basic instrument used for optical data storage is a scanning laser microscope. Each device contains a beam from a laser diode that is collimated, shaped and focused with an objective lens to produce a microscopic spot on the recording media. The reflected light is collected by the objective lens and directed to data and servo detectors with a beam splitter. Data density on the storage medium is primarily defined by the size and shape of the focused laser beam used to scan the data. Several interesting techniques have been used to shape the focused spot in a way that decreases the primary feature of the spot, thus increasing density. For example, both amplitude and phase filters have been used to decrease the central lobe, at the expense of increased sidelobe levels. Effects of the sidelobes can be minimized with special electronic circuits. The configuration of the readout optics also can influence density. That is, optical filters can be placed in the collection pupil to improve the system transfer function. When combined with electronic shaping circuits, the optical filters significantly improve device performance. This paper reviews the techniques used for beam shaping in optical data storage with an explanation of each technique and its success or failure.
• Beaudry, N. A., & Milster, T. D. (2000). Effects of object roughness on partially coherent image formation. Optics Letters, 25(7), 454-456.
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  PMID: 18064077;Abstract: Phase perturbations in the object plane of a partially coherent imaging system are found to produce artifacts in the aerial image. It is demonstrated that phase perturbations of as little as λ/30 rms can produce visible deformation in the final image for modest coherence factors, such as σc = 0.4. A combination of simulation and experiment is used to demonstrate the effects. Application to line-edge roughness in lithography is described. © 2000 Optical Society of America.
• Hirota, K., Milster, T. D., Shimura, K., Zhang, V., & Jo, J. S. (2000). Near-field phase change optical recording using a GaP hemispherical lens. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 39(2 B), 968-972.
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  Abstract: A GaP solid immersion lens and a modified liquid immersion lens (MLIL) are studied. The phase change marks exhibit a diameter of approximately 200 nm when recorded by the MLIL. ©2000 Publication Board, Japanese Journal of Applied Physics.
• Hirota, K., Milster, T. D., Zhang, V., & Erwin, J. K. (2000). Design of a near-field probe for optical recording using a 3-dimensional finite difference time domain method. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 39(2 B), 973-975.
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  Abstract: Tapered dielectric near-field probes are designed for optical recording by means of a 3-Dimensional finite difference time domain (FDTD) method. Probe fabrication is attempted with a double-exposure holographic technique. ©2000 Publication Board, Japanese Journal of Applied Physics.
• Jo, J. S., Milster, T. D., & Erwin, J. (2000). Amplitude and phase apodization caused by focusing light through an evanescent gap in SIL recorders. Proceedings of SPIE - The International Society for Optical Engineering, 4081, 135-142.
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  Abstract: High numerical aperture(NA) vector diffraction theory is used to analyze a near field optical system using a solid immersion lens (SIL). The amplitude and phase of the transmitted light through the system changes as a function of the air gap height as well as indices of refraction, incident angle, etc. We call these `amplitude apodization' and `phase apodization'. The characteristics of those are done using supergaussian form. The effects of amplitude and phase apodization on irradiance are investigated for various index of refraction and air gap height.
• Milster, T. D. (2000). Near-field optical data storage: Avenues for improved performance. Proceedings of SPIE - The International Society for Optical Engineering, 4081, 126-134.
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  Abstract: Because they produce small spot size, near-field techniques are applied to optical data storage systems in order to increase recording density. For data storage, the optical near field is defined in terms of evanescent coupling between the system used to read data and the recording layer. Two practical implementations that use evanescent energy are aperture probes and solid immersion lenses (SILs). In this paper, the basic characteristics of these systems are reviewed, and some considerations for improving performance are discussed. Combinations of SILs and apertures could produce data storage systems with ultra-fine resolution and good detection characteristics.
• Milster, T. D. (2000). Near-field optics: A new tool for data storage. Proceedings of the IEEE, 88(9), 1480-1489.
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  Abstract: Evanescent energy can be used to produce extremely small optical spots. Two practical implementations that use evanescent energy are aperture probes and solid immersion lenses (SILs). For data storage, the optical near field is defined In terms of evanescent coupling between the system used to read data and the recording layer. Because of the small spot size, near-field techniques are applied lo optical data storage systems in order to increase recording density. Both aperture-type systems and SIL systems show good promise of achieving densities of more than ISO Cb/in2. The characteristics and performance of several systems are compared, and future near-field technologies are discussed. © 2000 IEEE.
• Shimura, K., Milster, T. D., Jo, J. S., & Hirota, K. (2000). Pupil plane filtering for optical pickup heads with effective numerical aperture of 1.1 and 2.0. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 39(2 B), 897-901.
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  Abstract: A pupil plane filtering technique is applied to data signal detection in an optical data storage system that uses a solid immersion lens (SIL) and a quadrilayer phase change recording medium. Two systems that have the effective numerical aperture (NAEFF) of 1.1 and 2.0 are investigated. A new filter is designed for the NAEFF = 2.0 system on the basis of this study. We have confirmed by numerical calculations that the technique improves signal contrast, which is defined by the ratio of the difference signal to the sum signal between the homogeneous crystalline area and the homogeneous amorphous area. We have also confirmed that the technique makes the contrast less sensitive to the gap width between the SIL and the recording medium. The vectorial feature of the light is considered in the calculations. The calculated irradiance distributions and signal levels for the system with NAEFF = 1.1 are confirmed by experiments. © 2000 Publication Board, Japanese Journal of Applied Physics.
• Upton, R. S., & Milster, T. D. (2000). Exit pupil patterns from optical disks. Proceedings of SPIE - The International Society for Optical Engineering, 4081, 143-154.
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  Abstract: The modulation of the irradiance in the exit pupil of an optical data storage scanning system is described by analyzing the behavior of scan-dependent interference fringes. These fringes are grouped into three independent irradiance components. The variation of the exit pupil irradiance pattern as a function of groove depth is discussed.
• Upton, R. S., Akhavan, F., Milster, T. D., Schweisguth, M., Bletscher, W. L., Erwin, J. K., & Nichol, A. M. (2000). Electronic crosstalk cancellation with a quadrant cell detector. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 39(2 B), 837-839.
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  Abstract: Single beam electronic crosstalk cancellation by a quadrant cell detector placed in the exit pupil of an optical data storage system is experimentally shown to reduce crosstalk levels by - 10dB and improve jitter by a factor of 2.5 for double density recorded compact disk rewritable media (CD-RW). Simulations show -21 dB reduction in crosstalk levels for CD-RW. © 2000 Publication Board, Japanese Journal of Applied Physics.
• Akhavan, F., & Milster, T. D. (1999). CD-R and CD-RW optical disk characterization in response to intense light sources. Proceedings of SPIE - The International Society for Optical Engineering, 3806, 84-92.
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  Abstract: Several commercial CD-R and CD-RW optical recording disks are exposed to intense white light sources (Halogen Tungsten and High-Intensity Discharge) at different exposure times under three minutes. Main analog playback parameters for CD-R and CD-RW optical recording disks are identified and characterized. The contents of a test disk is recorded onto each CD-R and CD-RW disk using a commercial rewritable/recordable disk drive. For each disk, written marks are imaged under a Nomarsky/Bright field optical microscope before and after exposure. Using a dynamic tester carrier-to-noise ratio and timing jitter are determined before and after exposure. AZO-dye CD-R disks, cyanine-dye CD-R disks, and CD-RW disks show considerable reduction in written mark contrast after exposure. Pthalocyanine-dye CD-R disks do not show significant changes in the mark contrast after exposure. Dynamic tester results confirm the mark contrast results and give insight into playback behavior of exposed disks.
• Beaudry, N. A., & Milster, T. D. (1999). Effects of mask roughness and condenser scattering in EUVL systems. Proceedings of SPIE - The International Society for Optical Engineering, 3676(II), 653-662.
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  Abstract: The wavefront reflected from extreme ultraviolet lithography (EUVL) mirror and mask surfaces can contain a non-negligible amount of phase variation due to roughness of the mirror surfaces and variations in multilayer thin-film coatings. We examine the characteristics of image and pattern formation as a function of phase variations originating at the mask surface and at condenser mirrors. A theoretical development and a Monte-Carlo simulation are used to show relationships between statistics of the phase variations and the mask pattern, coherence factor, and numerical aperture of the projection camera. Results indicate that it is possible to produce nearly 1% line-edge roughness in a photoresist pattern from moderate values of phase variations.
• Hirota, K., Milster, T. D., & Zhang, Y. (1999). Design of a nearfield probe for optical recording using a 3-dimensional finite difference time domain method. Proceedings of SPIE - The International Society for Optical Engineering, 3864, 261-263.
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  Abstract: The electromagnetic field of tapered dielectric probes for optical recording was examined by the 3D finite-difference time-domain method. The probes with a diameter at the bottom surface of approximately 1/n wavelength exhibited high light beam throughput when compared with conventional metal-coated near-field scanning optical microscope probes. The beam sizes inside the recording media, using LaSFN9 glass and GaP probe, were estimated to be 0.75 and 0.43 wavelength, respectively. The computational study of the scattering field from the recorded mark show that these probe can work in the reflection-detection mode.
• Hirota, K., Milster, T. D., Shimura, K., Zhang, Y., & Jo, J. S. (1999). Nearfield phase change optical recording using a GaP hemispherical lens. Proceedings of SPIE - The International Society for Optical Engineering, 3864, 361-363.
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  Abstract: The solid immersion lens (SIL) and modified liquid immersion lens (MLIL) using a GaP lens resolve the 400 nm pitch periodical structure are demonstrated. The edge response of the MLIL is 300 nm, which is approximately 1/3 as small as that of conventional objective lens. The amorphous marks, 200 nm in diameter, can be recorded and read by the MLIL and a red semiconductor laser.
• Milster, T. D. (1999). Chromatic correction of high-performance solid immersion lens systems. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 38(3 B), 1777-1779.
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  Abstract: The chromatic dispersion of hyper-hemisphere solid immersion lens (SIL) systems is discussed. A simple correction mechanism using a diffractive optical element (DOE) is presented that improves the chromatic aberration by a factor of ten. © 1999 Publication Board, Japanese Journal of Applied Physics.
• Milster, T. D., & Upton, R. S. (1999). Fundamental principles of crosstalk in optical data storage. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 38(3 B), 1608-1613.
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  Abstract: Cross talk in the read out signal resulting from narrow track pitches is analyzed with a Babinet decomposition of the light reflected from the disk surface. Results indicate that the commonly used technique of measuring cross talk does not adequately describe the temporal behavior of cross talk effects because the intermodulation of the scan-track mark pattern and the adjacent-track mark pattern is not considered. Our analysis takes this inter-modulation into account and shows its significance. The analysis presents a fundamentally new way to conceptualize cross talk in which effects due to different terms of the Babinet decomposition can be studied separately or combined in meaningful signal groups that relate directly to measurements. Example calculations are presented that illustrate the behavior of the readout signal from optical disks that might be used for land-and-groove recording. Quantification of cross talk effects are presented with respect to shifts of signal transitions. © 1999 Publication Board, Japanese Journal of Applied Physics.
• Milster, T. D., Gregg, D. P., & Wilson, K. C. (1999). Crescent geometry for an optical ribbon recorder. Proceedings of SPIE - The International Society for Optical Engineering, 3864, 106-108.
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  Abstract: Several geometries have been presented in the literature for optical tape recorders. A new scanning architecture called crescent scanning is addressed. The primary features of this architecture include a new scanning mechanism and the resulting crescent-like pattern of tracks across the width of the ribbon. In addition, the ribbon is contained in a sealed or semi-sealed cartridge where the optical surface of the ribbon does not come into contact with any surface other than rolling upon the tape itself. The concepts related to scanning the ribbon are discussed.
• Milster, T. D., Jo, J. S., & Hirota, K. (1999). Roles of propagating and evanescent waves in solid immersion lens systems. Applied Optics, 38(23), 5046-5057.
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  PMID: 18323997;Abstract: The electromagnetic field incident on the thin-film layers in a solid immersion lens (SIL) system is decomposed into contributions from homogeneous and inhomogeneous waves, which are commonly referred to as propagating and evanescent waves, respectively. The homogeneous and the inhomogeneous parts have different properties with respect to the field distribution in the gap and inside the recording layers. The homogeneous part is shown to diffract like a focused wave with a numerical aperture of 1, and the inhomogeneous part decays exponentially away from the bottom of the SIL. Two examples are discussed in detail, and the concept of a vector illumination system transfer function, which includes effects of the recording layers, is introduced.
• Milster, T. D., Jo, J. S., Hirota, K., Shimura, K., & Zhang, Y. (1999). The nature of the coupling field in optical data storage using solid immersion lenses. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 38(3 B), 1793-1794.
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  Abstract: The field incident onto the interface between the solid immersion lens (SIL) and recording medium is decomposed into two parts that exhibit different behavior as the beam propagates through the recording layers. The homogeneous part is shown to diffract, and the inhomogeneous part decays exponentially away from the bottom of the SIL. Reflection and signal contrast are calculated for a phase-change recording medium. The dependences of the signal contrast on the gap width, the refractive index of gap and the SIL arc analyzed. © 1999 Publication Board, Japanese Journal of Applied Physics.
• Milster, T. D., Shimura, K., Jo, J. S., & Hirota, K. (1999). Pupil-plane filtering for improved signal detection in an optical data-storage system incorporating a solid immersion lens. Optics Letters, 24(9), 605-607.
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  PMID: 18073797;Abstract: The data-signal detection of an optical data-storage system with a solid immersion lens (SIL) was improved using a pupil-plane filtering technique. The technique improves the signal contrast and reduces the cancellation of positive and negative signal contributions in the pupil. Furthermore, the technique makes the signal contrast less sensitive for relatively large gap widths.
• Milster, T. D., Upton, R. S., & Luo, H. (1999). Objective lens design for multiple-layer optical data storage. Optical Engineering, 38(2), 295-301.
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  Abstract: A number of aberration compensation systems are investigated for use with multiple-layer optical data storage. A Burch-type objective lens in conjunction with a Galilean telescope is found to be a compact, simple and effective optical system for spherical aberration Compensation. © 1999 Society of Photo-Optical Instrumentation Engineers.
• Shimura, K., Milster, T. D., Hirota, K., & Jo, J. S. (1999). Pupil plane filtering for improved signal detection in an optical data storage system incorporating a solid immersion lens. Proceedings of SPIE - The International Society for Optical Engineering, 3864, 378-380.
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  Abstract: A new method that significantly improves signal contrast when using solid immersion lens (SIL) optics with a certain phase-change recording layer structure is proposed. Linearly polarized light is used to illuminate the lens that focuses light onto the medium, and a special filter is used to block negative signal components from reaching the detector after light is reflected from the recording layers. Numerical calculation showed that the minimum contrast can be improved from near zero to over 0.25 by the filtering.
• Upton, R. S., Akhavan, F., Milster, T. D., Bletscher, W. L., Erwin, J., Nicol, A. M., & Flores, S. (1999). Cross talk cancellation with a quadrant cell detector. Proceedings of SPIE - The International Society for Optical Engineering, 3864, 26-28.
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  Abstract: Cross talk levels of -20.8 dB for double-density tracks on compact disk-RW (CD-RW) media are demonstrated by using quadrant pupil detection (QPD) signal cancellation with a single focused spot. Cross talk cancellation in a single optical beam systems by means of a quadrant cell detector is analyzed. Results indicate that cross talk arising from single-tone frequency patterns can be corrected by simple amplitude and phase scaling, while dual-tone cross talk cancellation may require the use of shading bands.
• Hirota, K., Jo, J. S., & Milster, T. D. (1998). High density phase change optical recording using a solid immersion lens. Proceedings of SPIE - The International Society for Optical Engineering, 3401, 34-39.
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  Abstract: The use of solid immersion lens (SIL) optical head for high density phase change recording was demonstrated. Amorphous marks of 300nm in diameter were written and erased using the SIL (NAeff=1.1). This technique can be further improved and can achieve a higher density recording by using a shorter wavelength semiconductor laser and a higher refractive index lens mounted on a near contact or in-contact head slider.
• Milster, T. D. (1998). New way to describe diffraction from optical disks. Applied Optics, 37(29), 6878-6883.
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  PMID: 18301504;Abstract: An efficient decomposition of the diffraction pattern from optical disks that yields insight into the origin and the characteristics of various signals is described. The Bahinet principle is used to separate components that describe the data signal, servo signals, and three types of cross talk. The construction of a basis set that yields efficient calculation for optimization studies is described. Two media types are considered as examples. Several applications are also described, including an explanation for the origin of the differential phase-detection tracking signal that is used with DVD-ROM media. © 1998 Optical Society of America.
• Milster, T. D., & Beaudry, N. A. (1998). Scattering and coherence in EUVL. Proceedings of SPIE - The International Society for Optical Engineering, 3331, 537-543.
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  Abstract: We illustrate the importance of considering scattering from the illuminator in extreme ultraviolet lithography (EUVL) systems. Our results indicate that a significant mount of amplitude modulation noise is present in the aerial image if scatter is present in a Köhler illuminator. The effect depends on the spatial frequency of the pattern on the mask, the numerical aperture of the projection camera, the coherence factor, and placement of the plane in the illuminator where the scattering occurs.
• Milster, T. D., Wehrenberg, P. J., & Kubota, S. (1998). Proceedings of SPIE - The International Society for Optical Engineering: Introduction. Proceedings of SPIE - The International Society for Optical Engineering, 3401, ix.
• Tang, H., & Milster, T. D. (1998). Modulation transfer function of bar code scanning. Optical Engineering, 37(9), 2574-2580.
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  Abstract: Bar code scanners are ubiquitous in supermarkets. As a bar code is passed over a scanner, a laser beam scans across the bar code. The scattered light is modulated by the reflectivity of the bars and spaces of the bar code. The bar code scanning process can be described as a 1-D convolution of the scanning laser profile and the bar code reflectivity function. The modulation transfer function (MTF) of bar code scanning is the Fourier transform of the marginal profile of the laser beam. The properties of the MTF of bar code scanning is similar to that of an incoherent imaging system. Measurements of the MTF of bar code scanning at one focal position are presented. The experimental results are then discussed. © 1998 Society of Photo-Optical Instrumentation Engineers.
• Upton, R. S., & Milster, T. D. (1998). Complex-plane description of differential phase detection in optical data storage. Proceedings of SPIE - The International Society for Optical Engineering, 3401, 263-271.
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  Abstract: Differential phase detection (DPD) is a method of generating a tracking error signal from rotation of the irradiance pattern formed in the pupil of an optical data storage system. The amount of rotation is related to the distance between the scanning spot and the center of the track being scanned. Media parameters, such as reflectivities of the marks and land and the groove depth affect the DPD signal. The representation of mark and land reflectivity vectors on a complex plane diagram proves to be an elegant technique for designers to optimize a given medium for DPD.
• Flagello, D. G., & Milster, T. D. (1997). High-numerical-aperture effects in photoresist. Applied Optics, 36(34), 8944-8951.
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  PMID: 18264448;Abstract: Two-beam and three-beam vector interference in thin photoresist films is used to illustrate the striking differences between s-polarized and p-polarized high-numerical-aperture illumination. Both simulations and experiments are performed for several cases, including undyed photoresist on silicon, dyed photoresist on silicon, and the addition of an antireflective layer between the photoresist and the silicon. A 0.85 numerical-aperture system is examined. The major differences between s- and p-polarized illumination include elliptical versus rectangular features and lower contrast for p-polarized images. © 1997 Optical Society of America.
• Froehlich, F. F., & Muster, T. D. (1997). Mechanical resonance behavior of near-field optical microscope probes. Applied Physics Letters, 70(12), 1500-1502.
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  Abstract: The mechanical resonance behavior of near-field optical microscope probes is examined with a simple experiment on a flat pyrex sample. While our tapered-fiber probe is locked on the second resonance for servo control, the vibration characteristics around the first resonance are investigated. We find that the overwhelming cause of decreased vibration amplitude as the tip approaches the sample is an increase in damping presumably due to a fluidlike layer on the sample. A small additional effect is also observed that could be due to force derivatives. © 1997 American Institute of Physics.
• Milster, T. D. (1997). A new way to describe diffraction from optical disks. Proceedings of SPIE - The International Society for Optical Engineering, 3109, 229-234.
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  Abstract: We describe an efficient decomposition of the diffraction pattern from optical disks that yields might into the origin and characteristics of various signals. Babinet's Principle is used to separate components that describe the data signal, servo signals, and two types of crosstalk. The construction of a basis set is described that yields efficient calculation for optimization studies. Two media types are considered as examples. Several applications are also described, including an explanation for the origin of the differential phase detection tracking signal that is used with DVD-ROM media.
• Milster, T. D. (1997). Optimization of DVD media parameters. Topical Meeting on Optical Data Storage - Digest of Technical Papers, 34-35.
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  Abstract: The dependence of the data signal modulation and the quadrant pupil detection (QPD) amplitude on mark reflectivity, land reflectivity, and mark/land phase difference on reflection is reported. The modelling parameters was performed by utilizing the scalar diffraction calculation facility in OPTISCANTM, which is a new optical system simulation program.
• Milster, T. D. (1997). User-friendly diffraction modeling program. Topical Meeting on Optical Data Storage - Digest of Technical Papers, 60-61.
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  Abstract: The simulation of optical systems with ray tracing or diffraction modeling is a design and analysis requirement for optical data storage systems. This can be achieved by utilizing OPTISCAN, a program that runs in an MATLAB language environment, for the optical data storage systems modeling. OPTISCAN simulates and solves the common problem of simulation codes. It provides a graphical user interface (GUI) that makes the programming less complicated and makes the OPTISCAN user-friendly. The GUI feature of the OPTISCAN and an optical disk application are presented.
• Milster, T. D., & Luo, H. (1997). Objective lens design for multiple-layer optical data storage. Topical Meeting on Optical Data Storage - Digest of Technical Papers, 83-84.
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  Abstract: The methods of compensating aberrations in multiple-layer storage with common objective lens designs are discussed. A new class of objective lenses that could be useful for this technology is also introduced. Mechanical change in the compensation optics to focus at different depths are not entirely satisfactory either due to a restricted range of compensated thickness or due to extremely tight alignment tolerances. Common objective-lens shapes do not perform well off axis due to a large amount of coma. Instead, changing the shape so that the radii are symmetric and nearly equal to the surface separation produces excellent results.
• Milster, T. D., Upton, R. S., & Luo, H. (1997). Objective lens design for multiple-layer optical data storage. Proceedings of SPIE - The International Society for Optical Engineering, 3109, 142-149.
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  Abstract: A finite conjugate, high numerical aperture objective configured with a compensating telescope was designed to read and write in multiple layer optical disk storage system. The system was capable of focusing onto individual data layers with high numerical aperture and good field performance. A number of finite conjugate aberration compensation systems was investigated. The results showed that a Burch-type objective lens in conjuction with a Galilean telescope was a compact, simple and effective optical system for spherical aberration compensation.
• Russell, T. H., & Milster, T. D. (1997). Polarization switching control in vertical-cavity surface-emitting lasers. Applied Physics Letters, 70(19), 2520-2522.
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  Abstract: Orthogonal polarizations within vertical-cavity surface-emitting lasers (VCSEL) lase at slightly different wavelengths. We describe the use of optical feedback to confine polarization variations to reproducible injection currents. An external cavity is used to select specific wavelengths that reflect back into the VCSEL, hence, changing the cavity Q for the different polarization states. With this control, we can change the polarization state of the laser output. © 1997 American Institute of Physics.
• Schlichting, W., Faris, S., Fan, B., Haag, J., Zhijian, L. u., Kane, S., Le, L. i., Milster, T., & Luo, H. (1997). Recording and readout of a cholesteric liquid crystal based multilayer disk. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 36(1 B), 587-588.
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  Abstract: A novel approach to optical storage based on layering of cholesteric liquid crystal (CLC) media is being investigated. CLC media have been chosen due to their unique property of selective reflection, whereby a CLC film reflects light of a characteristic wavelength and polarization handedness with near-zero loss while transmitting all other light. This new technology has the potential of enabling terabyte storage on a single optical disk. A two-layer disk with 5 μm data marks was recorded and crosstalk-free readout was demonstrated by selecting the correct circular polarization state of a 514 nm laser.
• Flagello, D. G., Milster, T., & Rosenbluth, A. E. (1996). Theory of high-NA imaging in homogeneous thin films. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 13(1), 53-64.
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  Abstract: A description is given of a modeling technique that is used to explore three-dimensional image distributions formed by high numerical aperture (NA > 0.6) lenses in homogeneous, isotropic, linear, and source-free thin films. The approach is based on a plane-wave decomposition in the exit pupil. Factors that are due to polarization, aberration, object transmittance, propagation, and phase terms are associated with each plane-wave component. These are combined with a modified thin-film matrix technique in a derivation of the total field amplitude at each point in the film by a coherent vector sum over all plane waves. One then calculates the image distribution by squaring the electric-field amplitude. The model is used to show how asymmetries present in the polarized image change with the influence of a thin film. Extensions of the model to magneto-optic thin films are discussed. © 1996 Optical Society of America.
• Milster, T. D. (1996). Combination of ray-trace and diffraction modeling to describe coupling laser diodes to fibers and waveguides. Proceedings of SPIE - The International Society for Optical Engineering, 2610, 194-202.
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  Abstract: We describe a design tool for analyzing coupling between laser diodes and waveguides. The calculation includes adding system aberration information from a ray trace to a diffraction calculation in order to estimate the distribution of light incident on the waveguide. The overlap integral is used to calculate coupling efficiency. A simple example is given that analyzes coupling from a single-mode laser diode to a single-mode fiber using a ball lens. Calculations are compared with experimental results.
• Milster, T. D., & Walker, E. P. (1996). Mechanism for improving the signal-to-noise ratio in scanning optical microscopes. Optics Letters, 21(16), 1304-1306.
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  PMID: 19876333;Abstract: We demonstrate an improved signal-to-noise ratio in a scanning optical microscope used to read out information from a magneto-optical data storage layer. By placing a shading band in the return path of the optical system we can reduce noise by as much as 3 dB in certain spatial frequency ranges. The signal-to-noise ratio improvement arises from differences in the signal and noise distributions in the pupil of the optical system. Although the experimental results are shown only in one dimension, the concept is applicable to two-dimensional scanning of low-contrast samples. © 1996 Optical Society of America.
• Milster, T. D., Chen, Z., Walker, E. P., Tuell, M. T., & Gage, E. C. (1996). Optical data storage readout with quadrant pupil detection. Applied Optics, 35(14), 2471-2476.
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  PMID: 21085384;Abstract: A novel detection scheme that uses combinations of quadrant signals derived in a pupil of the optical system is described for optical storage devices. The signals arise because of an asymmetry in the reflected light distribution when the focused spot scans data with a nonzero tracking offset. Theoretical and scalar diffraction characterization indicates that the signals may be useful for improved data density by reducing intertrack interference (cross talk). The signals may also be useful for providing a tracking error signal. © 1996 Optical Society of America.
• Vernold, C. L., & Milster, T. D. (1996). Alignment of an optical axis to a rotating mechanical axis using grating phase modulation. Proceedings of SPIE - The International Society for Optical Engineering, 2730, 639-642.
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  Abstract: We describe a technique for aligning the axis of an optical system to the axis of a rotating mechanical system. The optical system is focused onto a linear grating that rotates in conjunction with the mechanical system. Light reflected from the grating produces an interference pattern in the pupil of the optical system. Temporal modulation of the fringes in the interference pattern is observed as the mechanical system rotates of the optical and mechanical axes are misaligned. Our application for this technique is in aligning an optical and mechanical system for writing circularly symmetric computer generated holograms. Experimentally we demonstrate alignments to accuracies of 0.1 micrometers.
• Milster, T. D. (1995). Design issues in optical data storage. Proceedings of SPIE - The International Society for Optical Engineering, 2383, 382-389.
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  Abstract: We present an introduction to some of the critical considerations in designing pickup systems for optical data storage.
• Froehlich, F. F., & Milster, T. D. (1994). Minimum detectable displacement in near-field scanning optical microscopy. Applied Physics Letters, 65(18), 2254-2256.
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  Abstract: The optical geometry of the beam diffraction method was described, and an equation for the minimum detectable displacement (MDD) was developed. Theoretical calculations and experimental measurements of the MDD were presented and compared. The minimum detectable displacement of a nearfield optical microscopy tapered fiber probe was measured using the beam diffraction technique. The shot-noise limited sensitivity value obtained agreed well with a theoretical value computed with the assistance of a scalar diffraction model. The beam diffraction method is deemed simple to execute and is suitable to the orthogonal probe-sample geometry utilized in near-field microscopes.
• Schlichting, W., Milster, T. D., Wang, M. S., & Brucker, C. (1994). Signal and noise with a magnetic circular dichroism detection system in optical data storage. Journal of Applied Physics, 75(5), 2322-2324.
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  Abstract: This paper presents a comparative study of magnetic circular birefringence (MCB) to magnetic circular dichroism (MCD) detection of the Kerr effect in a magneto-optical head with circular polarized light incident on a Co/Pt superlattice medium. Results show that the MCD system can deliver a CNR of 40 dB despite the loss of in capability to reject common mode noise, which is less than the requirement for error-free recording. Thus it can be applied only to systems that can tolerate a higher bit error rate or operate at lower data frequency.
• Froehlich, F. F., Milster, T. D., & Uber, R. (1993). High-resolution optical lithography with a near-field scanning subwavelength aperture. Proceedings of SPIE - The International Society for Optical Engineering, 1751, 312-320.
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  Abstract: We report on a novel method for generating sub-micron lithographic patterns in photoresist through the use of a scanned sub-wavelength optical aperture. The aperture consists of the tip of a single-mode optical fiber that is drawn down to a diameter of 80 nm and coated with aluminum. The fiber tip is manipulated with a modified scanning tunneling microscope (STM) that brings the tip into proximity of a photoresist-coated substrate. The resolution is primarily a function of the aperture diameter and tip-to-sample separation. A linewidth of 200 nm has been achieved in preliminary experiments.
• Milster, T. D., Wang, M. S., Weiquan, L. i., & Walker, E. (1993). Optical filtering in the collection path of a data storage device. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 32(11 B), 5397-5401.
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  Abstract: The effects of placing a shading band in the collection path of a magneto-optical data storage device are presented. The shading band consists of an opaque region in the center of the collection aperture, which reduces the low-frequency response of the system without affecting the high-frequency response. This partially equalizes the system transfer function. Dynamic measurements indicate that the noise is also reduced in the low-frequency region, thus not significantly affecting the narrow-band carrier-to-noise ratio (CNR). The integrated signal-to-noise ratio (SNR) shows slight improvement in the high-frequency region.
• Schlichting, W., Milster, T. D., & Campillo, C. J. (1993). Optical data storage based on magnetic circular dichroism. Applied Physics Letters, 62(22), 2751-2753.
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  Abstract: An alternative to differential detection in optical data storage is magnetic circular dichroism (MCD) detection. The MCD system has increased light efficiency when compared to the commonly used differential detection method. Also, the signal amplitude for MCD detection can be twice as large as for differential detection when an s-p phase difference of 90°is introduced in the medium. Modeling results show that a thin-film device can introduce the necessary s-p phase difference. Our signal-to-noise analysis indicates that the MCD system rejects polarization noise. Experimental results on coupon samples verify that the signal from MCD detection can be twice as large as from differential detection.
• Wang, M. S., & Milster, T. D. (1993). Crosstalk cancellation using differential wax-wane focus servo technique. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 32(11 B), 5277-5283.
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  Abstract: We present studies of crosstalk cancellation using the differential wax-wane focus servo technique. A scalar diffraction model is employed to accurately predict its performance. The measured wavefront is implemented in the diffraction model and excellent agreement between experimental and modeling results is achieved. With measured system aberration, the tracking crosstalk is reduced from 0.7 μm in a single channel to less than 0.1 μm in the optimized differential channel. Comparisons to the astigmatic and pupil obscuration focus error detection techniques are given. Without any aberration, the differential wax-wane technique has a tracking crosstalk amplitude of 0.04 μm compared to about 0.25 μm in other techniques.
• Wang, M. S., & Milster, T. D. (1993). Differential wax-wane focus servo. Applied Optics, 32(25), 4797-4807.
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  Abstract: A differential wax-wane servo method for optical data storage applications is reported, and its performance studied by a scalar diffraction model. The advantages of this technique over single wax-wane focus servo method are 2 times higher gain, better lock-on range, and 10 times better linearity with respect to rms deviation.
• Flagello, D. G., & Milster, T. D. (1992). Three-dimensional modeling of high-numerical-aperture imaging in thin films. Proceedings of SPIE - The International Society for Optical Engineering, 1625, 246-261.
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  Abstract: This paper describes a modelling technique used to explore three dimensional (3D) image irradiance distributions formed by high numerical aperture (NA > 0.5) lenses in homogeneous, linear films. This work uses a 3D modelling approach that is based on a plane-wave decomposition in the exit pupil. Each plane wave component is weighted by factors due to polarization, aberration, and input amplitude and phase terms. This is combined with a modified thin-film matrix technique to derive the total field amplitude at each point in a film by a coherent vector sum over all plane waves. Then the total irradiance is calculated. The model is used to show how asymmetries present in the polarized image change with the influence of a thin film through varying degrees of focus.
• Milster, T. D., & Treptau, J. P. (1992). Combining ray-trace and diffraction analysis: a design example. Proceedings of SPIE - The International Society for Optical Engineering, 1625, 108-112.
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  Abstract: We present an example of using a combined ray trace and diffraction modeling code to simulate effects of objective-lens tilt in an optical data storage device.
• Milster, T. D., & Wong, J. N. (1992). Modeling and measurement of a micro-optic beam deflector. Proceedings of SPIE - The International Society for Optical Engineering, 1625, 78-83.
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  Abstract: We investigate the use of a unity-magnification micro-optic beam deflector. The deflector consists of two arrays of positively powered lenslets. The lenslets on each array are arranged in a square grid. Design criteriaare based on usefulness in optical data storage devices. The deflector is designed to operate over a ± 1.6° range of deflection angles. We compare modeling results with interferometric analysis of the wavefront from a single lenslet pair. Our results indicate that the device is nearly diffraction limited, but there are substantial wavefront errors at the edges and corners of the lenslets.
• Milster, T. D., & Treptau, J. P. (1991). Measurement of laser spot quality. Proceedings of SPIE - The International Society for Optical Engineering, 1414, 91-96.
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  Abstract: Several ways of measuring spot quality are compared. We examine in detail various figures of merit such as full-width-at-half maximum (FWHM), full-width-at-1/e2 maximum, Strehl ratio, and encircled energy. Our application is optical data storage, but results can be applied to other areas like space communications and high-energy lasers. We found that the optimum figure of merit in many cases is Strehl ratio.
• Milster, T. D., Trusty, R. M., Wang, M. S., Froehlich, F. F., & Erwin, J. K. (1991). Micro-optic lens for data storage. Proceedings of SPIE - The International Society for Optical Engineering, 1499, 286-292.
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  Abstract: A new type of microlens is described for data storage applications that has improved off-axis performance. The lens consists of a micro-Fresnel pattern on a curved substrate. The radius of the substrate is equal to the focal length of the lens. If the pattern and substrate are thin, the combination satisfies the Abbe sine condition. Therefore, the lens is free of coma. A 0.5 numerical aperture and 0.50 mm focal length lens are described in detail. A 0.16 numerical aperture lens was fabricated holographically, and results are presented.
• Milster, T. D., Wang, M. S., Froehlich, F. F., Kann, J. L., Treptau, J. P., & Erwin, K. E. (1991). Differential spot-size focus servo. Proceedings of SPIE - The International Society for Optical Engineering, 1499, 348-353.
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  Abstract: The performance of a differential spot-size (wax-wane) focus servo is described. Cross-talk from the tracks is analyzed in the single detector and differential focus circuits. Magnitude of the cross-talk is reduced by a factor of three in the differential circuit. A false FES signal is present when the spot crosses sector marks at an angle.
• Treptau, J. P., Milster, T. D., & Flagello, D. G. (1991). Laser beam modeling in optical storage systems. Proceedings of SPIE - The International Society for Optical Engineering, 1415, 317-321.
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  Abstract: A computer model has been developed that simulates light propagating through an optical data storage system. This paper will discuss a model of a laser beam that originates at a laser diode, propagates through an optical system, interacts with a optical disk, reflects back from the optical disk into the system, and propagates to data and servo detectors.
• Milster, T. D., Benedict, M. K., & Stahl, R. P. (1990). Laser diode requirement for magneto-optical storage devices. Proceedings of SPIE - The International Society for Optical Engineering, 1316, 143-149.
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  Abstract: There are several characteristics of laser diodes that influence the performance of a magneto-optical (MO) storage device. A few of the important optical characteristics include divergence angles, wavelength, astigmatism, polarization, and power output. Due to the large variation in these characteristics from commercial devices, compromises must be made in order to design an optical system that is manufacturable. In this paper we discuss how variations in the laser optical characteristics affect spot quality on the recording medium. Optical characteristics of a sample population of laser diodes are measured, and a hypothetical optical system is evaluated.
• Milster, T. D., N, J. A., Barrett, H. H., Landesman, A. L., Mar, L. S., Patton, D. D., Roney, T. J., Rowe, R. K., & III, R. S. (1990). A full-field modular gamma camera. Journal of Nuclear Medicine, 31(5), 632-639.
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  PMID: 2341900;Abstract: A modular gamma ray camera is described that gives useful image information over its entire crystal face. The lack of dead area on the periphery of the camera is made possible by a unique application of digital electronics and optimal position estimation using maximum likelihood (ML) estimates. The ML estimates are calculated directly from photomultiplier tube responses and stored in a lookup table, so the restriction of calculating the position estimates in separate circuitry is removed. Each module is designed to be optically and electronically independent, so that many modules can be combined in a large system. Results from a prototypical module, which has an active crystal area of 10 cm x 10 cm, are presented.
• Barrett, H. H., Smith, W. E., Myers, K. J., Milster, T. D., & Fiete, R. D. (1985). QUANTIFYING THE PERFORMANCE OF IMAGING SYSTEMS.. Proceedings of SPIE - The International Society for Optical Engineering, 535, 65-69.
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  Abstract: A figure of merit for characterizing the performance of medical imaging systems is suggested. It depends on statistical properties of the object and noise and on the transfer matrix specifying the imaging system.
• Milster, T. D., III, R. S., Barrett, H. H., Landesman, A. L., & Selberg, L. A. (1985). LOCALIZATION OF WEAK POINT SOURCES OF LIGHT.. Acta Polytechnica Scandinavica, Applied Physics Series, 97-100.
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  Abstract: A statistical estimation technique is introduced that is useful in determining parameters of an event, e. g. , position, energy, etc. , from a small number of detector signals.
• Paxman, R. G., Barrett, H. H., Smith, W. E., & Milster, T. D. (1985). Image reconstruction from coded data: II. Code design.. Journal of the Optical Society of America. A, Optics and image science, 2(4), 501-509.
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  PMID: 3872931;Abstract: A strategy is given for the design of coded apertures with respect to a given class of objects that are to be imaged. Previous knowledge of the first- and second-order statistics for the object class is assumed. The object class is characterized by its Karhunen-Loève eigenvectors and eigenvalues, whereas the imaging system is characterized by its singular-value decomposition. We introduce the concept of alignment in which the aperture parameters are adjusted until the system is tuned to measure the given object class well. A mean-square-error figure of merit that indicates degree of alignment is given, and alignment is performed by standard optimization techniques. We illustrate this technique with a simple proof-of-principle experiment. These concepts are general and may be applied to any linear imaging system.
• Milster, T. D., Selberg, L. A., Barrett, H. H., Landesman, A. L., & III, R. S. (1984). DIGITAL POSITION ESTIMATION FOR THE MODULAR SCINTILLATION CAMERA.. IEEE Transactions on Nuclear Science, NS-32(1), 748-752.
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  Abstract: Digital implementation of position estimation for the modular scintillation camera is presented. The modular camera system comprises an array of small, mechanically and electronically independent, all-digital scintillation cameras. This paper addresses how to best determine the event position given the photomultiplier-tube signals. Two Bayesian estimators are investigated, namely, maximum-likelihood and minimum-mean-square-error estimators. Both estimators performed similarly. The more important aspect of the estimation problem was found to be the shape of the detector responses as a function of position.
• Milster, T. D., Selberg, L. A., Barrett, H. H., Easton, R. L., Rossi, G. R., Arendt, J., & Simpson, R. G. (1983). MODULAR SCINTILLATION CAMERA FOR USE IN NUCLEAR MEDICINE.. IEEE Transactions on Nuclear Science, NS-31(1), 578-580.
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  Abstract: A 'modular' scintillation camera is discussed as an alternative to using Anger cameras for gamma-ray imaging in nuclear medicine. Each module is an independent gamma camera and consists of a scintillation crystal, light pipe and mask plane, photomultiplier tubes (PMTs), and processing electronics. Groups of modules efficiently image radionuclide distributions by effectively utilizing crystal area. Performance of each module is maximized by using Monte-Carlo computer simulations to determine the optical design of the camera, optimizing the signal processing of the PMT signals using maximum-likelihood estimators, and incorporating digital lookup tables. Each event is completely processed in 2 mu sec, and FWHM of the point-spread function over the crystal area is expected to be 3 mm. Both one-dimensional and two-dimensional prototypes are tested for spatial and energy resolution.

Proceedings Publications

• Brar, N., Zhang, Y., Kim, Y., Choi, H., Esparza, M. A., Kim, D., Yi, A., Cai, Y., Kim, G. H., Apai, D., & others, . (2023). Development of a MODE lens telescope. In Optical Fabrication and Testing.
• Milster, T. D., Brar, N., Zhang, Y., Kim, Y., Choi, H., Esparza, M., Kim, D., Yi, A., Cai, Y., Kim, G., & others, . (2023). Ultralightweight hybrid refractive/diffractive MODE telescopes for space applications. In Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems IV.
• Milster, T. D., Kim, Y., Brar, N., & Wang, Z. (2023). Theory and practice of high-harmonic diffractive surfaces. In ODS 2023: Industrial Optical Devices and Systems.
• Apai, D., Milster, T. D., Kim, D., Kim, Y., Schneider, G., Rackham, B. V., Arenberg, J., Choi, H., Esparza, M. A., Wang, Z., & others, . (2022). Nautilus Space Observatory: a very large aperture space telescope constellation enabled by scalable optical manufacturing technologies. In Optical Manufacturing and Testing XIV, 12221.
• Brar, N., Zhang, Y., Kim, Y., Yi, A., Cai, Y., Kim, G. H., & Milster, T. D. (2022). Precision glass molding technology for the MODE lens telescope. In Optical Manufacturing and Testing XIV, 12221.
• Choi, H., Esparza, M. A., Luu, R., Milster, T., Apai, D., & Kim, D. (2022). Autonomous closed-loop control for multi-segmented optic aligning and assembly. In Optical Manufacturing and Testing XIV, 12221.
• Esparza, M. A., Luu, R., Choi, H., Milster, T. D., Apai, D., & Kim, D. (2022). Progress towards alignment of Multi-Order Diffractive Engineered (MODE) lens segments using the Kinematically-Engaged Yoke System (KEYS) for optical performance testing. In Optical Manufacturing and Testing XIV, 12221.
• Katayama, R., & Takashima, Y. (2022). ODS 2022: Industrial Optical Devices and Systems. In Proc. of SPIE Vol, 12231.
• Kim, D., Milster, T. D., & Apai, D. (2022). Nautilus: The advent of large lens-based space telescopes. In European Physical Journal Web of Conferences, 266.
• Kim, Y., Esparza, M., Wang, Z., Brar, N., Choi, H., Kim, D., Apai, D., & Milster, T. D. (2022). Stray light analysis and testing of a MODE lens telescope. In Optical Manufacturing and Testing XIV, 12221.
• Milster, T. D., Kim, Y., & Wang, Z. (2022). Type 2 longitudinal chromatic aberration from a high-harmonic MODE lens and color corrector. In Optical Manufacturing and Testing XIV, 12221.
• Dmitrovic, S., Molnar, B., Kim, Y. S., Schumann, D., Foley, J., Shelley, J. T., & Milster, T. D. (2021). Progress toward a VUV Raman spectrometer to detect pathogens. In Label-free Biomedical Imaging and Sensing (LBIS) 2021, 11655.
• Kim, Y., Zhang, Y., & Milster, T. (2021). Molding error and its compensation in multi-order diffractive lens segmented telescope assembly. In Optical Fabrication and Testing.
• Milster, T. D., Wang, Z., & Kim, Y. (2021). Theory of color correction in high-harmonic diffractive lenses. In International Optical Design Conference.
• Wang, Z., Kim, Y., & Milster, T. (2021). Design of multi-order diffractive lens telescope for broadband application. In International Optical Design Conference.
• Apai, D., Milster, T. D., Kim, D., Bixel, A., Schneider, G., Rackham, B. V., Liang, R., & Arenberg, J. (2020). Nautilus: A Biosignature Survey in a Thousand Exo-Earths. In American Astronomical Society Meeting Abstracts# 235, 235.
• Apai, D., Milster, T. D., Kim, D., Schneider, G. H., Bixel, A., Benhamin, R., & Jonathan, A. (2020, November). Very Large-diameter, Ultralight Space Telescopes to Enable Large-scale Survey of Candidate Earth-like Planets for Signatures of Life. In ASCEND 2020, 2020, pp 8.
• Arenberg, J., Arenberg, J., Kim, G. H., Kim, G. H., Choi, H., Choi, H., Spires, O., Spires, O., Berkson, J., Berkson, J., Esparaza, M., Esparaza, M., Quach, H., Quach, H., Purvin, K., Purvin, K., Wang, Z., Wang, Z., Phan, A., , Phan, A., et al. (2020, August 2020). Disruptive space telescope concepts, designs, and developments: OASIS and Nautilus. In Topical Meeting 6 – Frontiers in Optical Metrology (EOS Annual Meeting 2020), 238 (2020), 06001.
• Choi, H., Esparza, M. A., Lamdan, A., Feng, Y., Milster, T., Apai, D., & Kim, D. W. (2020). In-process metrology for segmented optics UV curing control. In Optical Manufacturing and Testing XIII, 11487.
• Finan, E., & Milster, T. D. (2020). Phase retrieval methods for adaptive optics correction with diffractive samples. In ODS 2020: Industrial Optical Devices and Systems, 11500.
• Kim, Y., Wang, Z., & Milster, T. (2020). Optical Design and Analysis of Ultralight, Large Aperture Transmissive Lenses for Space Telescopes. In Frontiers in Optics.
• Milster, T. D. (2020). Complex diversity for multiple-wavelength single-shot phase retrieval (Conference Presentation). In Quantitative Phase Imaging VI, 11249.
• Milster, T. D., & Kuhn, W. P. (2020). Practical measurement of cell-phone camera lens focal length. In Optical System Alignment, Tolerancing, and Verification XIII, 11488.
• Milster, T. D., Apai, D., Kim, D. W., Kim, Y. S., Kim, G. H., Zhang, Y., Choi, H., Esparza, M., Spires, O., Liang, R., & others, . (2020). Progress toward optical design and fabrication of ultralight, large aperture transmissive lenses for space telescopes. In Frontiers in Optics.
• Zhang, Y., Zhou, W., Spires, O., Kim, Y. S., Yi, A., Liang, R., & Milster, T. D. (2020). Precision Glass molding for diffractive optics. In Frontiers in Optics.
• Apai, D., Milster, T. D., Kim, D., Bixel, A., Schneider, G., Rackham, B. V., Arenberg, J., & Liang, R. (2019, September). Nautilus Observatory: a space telescope array based on very large aperture ultralight diffractive optical elements. In Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems II, 11116, 08.
• Bendek, E., Sirbu, D., Henze, C., Belikov, R., Milster, T., Finan, E., & Pluzhnik, E. (2018). Sparse wavefront control: A new approach to high-contrast imaging. In Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave, 10698.
• Finan, E., Milster, T., & Kim, Y. (2018). Performance of an Adaptive Optics System in the Presence of Diffractive Grooves. In Frontiers in Optics.
• Jean, M., Bronson, R., Scott, R. P., Hart, M., Johnson, L., & Milster, T. D. (2017, July). Multi-wavelength Characterization of Multi-Order Diffractive Lenslet Arrays. In OSA Optical Fabrication and Test.
• Scott, R. P., Jean, M. A., Johnson, L., Gatlin, R., Bronson, R., Hart, M., & Milster, T. D. (2017, August). Lithographic manufacturing of adaptive optics components. In Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems, 10401.
• Eguchi, A., Lu, P., Kim, Y., & Milster, T. D. (2016). Characterization of multiphoton emission from aggregated gold nano particles. In SPIE Nanoscience+ Engineering.
• Pacheco, S., Salahieh, B., Zheng, G., Milster, T. D., Rodriguez, J., & Liang, R. (2016). Reflective Fourier ptychography (Conference Presentation). In SPIE BiOS.
• Vorndran, S. D., Johnson, L., Milster, T., & Kostuk, R. K. (2016). Measurement and analysis of algorithmically-designed diffractive optic for photovoltaic spectrum splitting. In Photovoltaic Specialists Conference (PVSC), 2016 IEEE 43rd.
• Ge, T., Yang, J., Summitt, C., Wang, S., Johnson, L., Zaverton, M., Milster, T., & Takashima, Y. (2015). High contrast and metal-less alignment process for all-polymer optical interconnect devices. In ADVANCED FABRICATION TECHNOLOGIES FOR MICRO/NANO OPTICS AND PHOTONICS VIII, 9374.
• Katayama, R., & Milster, T. D. (2015). PROCEEDINGS OF SPIE Optical Data Storage 2015. In OPTICAL DATA STORAGE 2015, 9587.
• Keyes, D. S., Jota, T. S., Gao, W., Luepke, D., Densmore, V., Kim, Y., Kim, G., & Milster, T. D. (2015). Optomechanical design and tolerance of a microscope objective at 121.6 nm. In OPTICAL MANUFACTURING AND TESTING XI, 9575.
• Milster, T. D., Lu, P., & Kieu, K. (2015). Potential of multi-photon reading and writing for optical data storage systems. In OPTICAL DATA STORAGE 2015, 9587.
• Summitt, C., Wang, S., Johnson, L., Zaverton, M., Ge, T., Milster, T., & Takashima, Y. (2015). Process optimization for a 3D optical coupler and waveguide fabrication on a single substrate using buffer coat material. In ADVANCED FABRICATION TECHNOLOGIES FOR MICRO/NANO OPTICS AND PHOTONICS VIII, 9374.
• Vorndran, S. D., Ayala, S., Wu, Y., Russo, J. M., Zaverton, M. A., Milster, T., & Kostuk, R. K. (2015). Freeform Surface Relief Diffractive Optic for Photovoltaic Spectrum Splitting. In 2015 IEEE 42ND PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC).
• Yang, J., Ge, T., Summitt, C., Wang, S., Milster, T., & Takashima, Y. (2015). All-polymer based fabrication process for an all-polymer flexible and parallel optical interconnect. In NANOENGINEERING: FABRICATION, PROPERTIES, OPTICS, AND DEVICES XII, 9556.
• Densmore, V. E., Kim, Y., Kim, G., & Milster, T. (2014). High NA Pupil Plane Image Polarimetry for Detection of Surface and Subsurface Damage in Optical Materials. In Frontiers in Optics, FTh3G--8.
• Densmore, V., Kim, Y. S., Milster, T., Wattson, M., & Kwok, D. (2014). A high-NA solid immersion objective for imaging a Blu-ray disc and investigating subsurface damage. In SPIE Optical Engineering+ Applications, 92010Q--92010Q.
• Eguchi, A., Lu, P., Milster, T., & Visscher, K. (2014). Proposal of a new imaging method with trapped gold nano particles and the properties of multi-photon emission. In Laser Science, JW3A--14.
• Johnson, L., Zaverton, M., Hashimoto, T., Milster, T., Kim, Y., & Felli, A. (2014). Freeform Diffractive Structure Writing through Maskless Lithography. In Laser Science, JW3A--7.
• Jota, T., Kim, Y., Kwok, D., Milster, T., & Luepke, D. S. (2014). Development of Optical Microscopy with a 121.6 nm Source. In Frontiers in Optics, JW3A--15.
• Katayama, R., & Milster, T. D. (2014). Optical Data Storage 2014 : 18-19 August 2014, San Diego, California, United States. In Optical Data Storage 2014.
• Katayama, R., & Milster, T. D. (2014). Optical Data Storage 2014. In Proc. of SPIE Vol, 9201, 920101--1.
• Lu, P., & Milster, T. (2014). Subsurface Damage Characterization with Nonlinear High Numerical Microscopy. In Frontiers in Optics, JW3A--9.
• Milster, T. D. (2014). Prospects and philosophy for high-density optical recording. In SPIE Optical Engineering+ Applications, 92010O--92010O.
• Summitt, C., Wang, S., Johnson, L., Zaverton, M., Ge, T., Milster, T., & Takashima, Y. (2014). Micro-optics fabrication by mask-based and mask-less mixed lithography process towards 3D optical circuits. In SPIE MOEMS-MEMS, 89740C--89740C.
• Wang, S., Summitt, C., Johnson, L., Zaverton, M., Milster, T., & Takashima, Y. (2014). Optical characterization of CMOS compatible micro optics fabricated by mask-based and mask-less hybrid lithography. In SPIE NanoScience+ Engineering, 91700F--91700F.
• Wang, S., Wang, S., Summitt, C., Ge, T., Johnson, L., Zaverton, M., Milster, T. D., Takashima, Y., Takashima, Y., & Wang, S. J. (2014). Alignment process for fabrication of mirror-based optical via using maskless lithography tool with buffer coat materials. In IMAPS (International Microelectronics Assembly & Packaging Society) 10th International Conference and Exhibition on Device Packaging (2014).
• Tamkin, J. M., & Milster, T. D. (2010). Analysis and Tolerancing of Structured Mid-Spatial Frequency Errors in Imaging Systems. In International Optical Design Conference 2010.
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  Structured mid-spatial frequency surface errors on aspheric optics can create ghost images and reduced contrast. This reduction in performance is shown to be non-linear with surface height using Fourier methods without small signal or statistical approximations. Tolerancing MSF errors can use traditional MTF metrics, and derives peak-to-valley limits on MSF surface height components. OCIS codes: (110.3000); (240.5770).
• Milster, T. D. (2004). Data Storage, Optical. In Encyclopedia of Applied Physics.
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  In its most general definition, optical data storage is simply using light as a tool to store and retrieve data. Optical data storage is found in popular consumer products. Compact Discs (CDs), Digital Versatile Discs (DVDs), and MiniDiscs (MDs), are all forms of optical data storage. More advanced forms of optical data storage include high-speed devices and library products. All optical data storage devices use optical principles to achieve high data density, rugged packaging, reliable information retrieval, and cost-effective production. There are many forms of optical storage media and many types of optical systems used to scan data. This chapter discusses the basic principles of optical data storage, types of commercial optical media available in 2003, several performance parameters, and some interesting prospects for future systems. Keywords: optical data storage; optical recording; compact disks; digital versatile disks; optical disks; optical memory; optical servos
• Milster, T. D. (1990). Characteristics Of Phase-Compensation Techniques In Magnetooptical Read-Back Systems. In Polarization Considerations for Optical Systems II.
• Milster, T. D., Barrett, H. H., Smith, W. E., Myers, K. J., & Fiete, R. D. (1985). Quantifying The Performance Of Imaging Systems. In Application of Optical Instrumentation in Medicine XIII.

Presentations

• Milster, T. D. (2015, June). Diffractive and Nano Optics Research. 2015 Raytheon MEOSTN Technical Symposium. Raytheon Missle Systems, Tucson.
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  Invited presentation