Rudolf Binder

Interests

Research

The main research focus in our group is on theoretical investigations of the optical properties of semiconductor structures. Our fundamental theoretical investigations of semiconductors are based on microscopic quantum-mechanical many-body theories and include ultrafast nonlinear optical processes in bulk semiconductors and quantum-well structures. Recent examples of research projects include electromagnetically-induced transparency, slow and fast light effects in bulk semiconductors and semiconductor heterostructures, nonlinear spectroscopy and all-optical switching applications of Bragg-spaced multiple quantum wells, optical refrigeration of semiconductors, optical four-wave mixing instabilities in semiconductor quantum wells systems, including microcavities, optical and elastic properties of semiconductor nanomembranes, optical properties of graphene, and also a topic not related to semiconductors, namely laser cooling of optical glass fibers.

Courses

Scholarly Contributions

Books

• Binder, R. (2016). Optical Properties of Graphene.

Chapters

• Everitt, H., Sandhu, A. S., Kwong, N., Roberts, A., & Binder, R. (2017). Nonlinear saddle point spectroscopy and electron-phonon interaction in graphene. In OPTICAL PROPERTIES OF GRAPHENE.
• Binder, R., & Kwong, N. (2016). Introductory Tutorial. In Optical Properties of Graphene.
• Binder, R., & Kwong, N. (2016). Microscopic Theory of Optical Refrigeration of Semiconductors. In Laser cooling: fundamentals and applications.
• Binder, R., Roberts, A., Kwong, N., Sandhu, A. S., & Everitt, H. (2016). Nonlinear saddle point spectroscopy and electron-phonon interaction in graphene. In Optical Properties of Graphene.
• Kwong, N., Binder, R., Nguyen, D., & Chavez-Pirson, A. (2016). Progress toward Laser Cooling of Thulium-doped Fibers. In Laser cooling: fundamentals and applications.

Journals/Publications

• Spotnitz, M., Kwong, N. H., & Binder, R. (2023). Collective fluctuation modes induced by terahertz radiation in a polariton laser. Phys. Rev. B, 107, 125309.
• Yu, Y., Dong, C., Binder, R., Schumacher, S., & Ning, C. (2023). Strain-Induced Indirect-to-Direct Bandgap Transition, Photoluminescence Enhancement, and Linewidth Reduction in Bilayer MoTe2. ACS Nano, 17, 4230-4238.
• Yuan, M., Rafailov, M., & Binder, R. (2023). Physics of photovoltaic signal modifications in p–n photodiodes. J. Appl. Phys,, 134, 174503.
• Klein, M., Binder, R., Koehler, M., Mandrus, D., Taniguchi, T., Watanabe, K., & Schaibley, J. R. (2022). Slow Light in a 2D Semiconductor Plasmonic Structure. Nat. Comm., 13, 6216.
• Binder, R., & Kwong, N. (2021). Metamorphosis of Goldstone and Soft Fluctuation Modes in Polariton Lasers. Phys. Rev. B.
• Kwong, N. H., Schaibley, J. R., & Binder, R. (2021). Effect of intravalley and intervalley electron-hole exchange on the nonlinear optical response of monolayer MoSe2. Phys. Rev. B, 245434.
• Luk, S., Vergnet, H., Lewandowski, P., Kwong, N., Galopin, E., Lemaitre, A., Roussignol, P., Tignon, J., Schumacher, S., Binder, R., & Baudin, E. (2021). All-optical beam steering using the polariton lighthouse effect. ACS Photonics.
• Spotnitz, M. E., Kwong, N. H., & Binder, R. (2021). Terahertz spectroscopy of semiconductor microcavity lasers: Photon Lasers. Phys. Rev. B, 104, 245434.
• Binder, R., Carcamo, M., & Schumacher, S. (2020). A transfer function replacement of phenomenological single-mode equations in semiconductor microcavity modeling. Applied Optics, 59 Focus Issue James. C. Wyant College of Optical Sciences, G112 - G119.
• Muccianti, C., Zachritz, S., Garlant, A., Eads, C., Badada, B., Alfrey, A., Koehler, M., Mandris, D., Binder, R., LeRoy, B. J., Monti Masel, O. L., & Schaibley, J. R. (2020). Coupled 2D Semiconductor−Molecular Excitons with Enhanced Raman Scattering. J. Phys. Chem. C, 27637 - 27644.
• Breddermann, P., Praschan, T., Heinze, D., Binder, R., & Schumacher, S. (2018). Microscopic theory of cavity-enhanced single-photon emission from optical two-photon Raman processes. Phys. Rev. B (Editor's Suggestion), 97, 125303.
• Lafont, O., Luk, S., Lewandowski, P., Kwong, N., Chan, K., Babilon, M., Leung, P., Gallopin, E., Lemaitre, A., Tignon, J., Schumacher, S., Baudin, E., & Binder, R. (2017). Controlling the optical spin Hall effect with light. Applied Physics Letters, 110, 061108.
• Lewandowski, P., Luk, S., Chan, K., Leung, P., Kwong, N., Binder, R., & Schumacher, S. (2017). Directional optical switching and transistor functionality using optical parametric oscillation in a spinor polariton fluid. Optics Express, 25, 31056 - 31063.
• Luk, S., Kwong, N., Lewandowski, P., Schumacher, S., & Binder, R. (2017). Optically controlled orbital angular momentum generation in a polaritonic quantum fluid. Physical Review Letters, 119, 113903.
• Luk, S., Lewandowski, P., Kwong, N., Baudin, E., Lafont, O., Tignon, J., Leung, P., Chan, K., Babilon, M., Schumacher, S., & Binder, R. (2017). Theory of optically controlled anisotropic polariton. J. Opt. Soc. Am. B, 35, 146-155.
• Binder, R., Roberts, A., Kwong, N., Sandhu, A. S., & Everitt, H. (2016). Global k-space analysis of electron-phonon interaction in graphene and application to M-point spectroscopy. Physical Review B, 93, 085414.
• Breddermann, D., Heinze, D., Binder, R., Zrenner, A., & Schumacher, S. (2016). All-optical tailoring of single-photon spectra in a quantum-dot microcavity system. Physical Review B.
• Lewandowski, P., Lafont, O., Baudin, E., Tsang, C., Leung, P., Luk, S., Gallopin, E., Lemaitre, A., Bloch, J., Tignon, J., Roussignol, P., Kwong, N., Binder, R., & Schumacher, S. (2016). Polarization dependence of nonlinear wave mixing of spinor polaritons in semiconductor microcavities. Physical Review B.
• Tse, Y., Chan, K., Luk, M., Kwong, N., Leung, P., Binder, R., & Schumacer, S. (2015). A population-competition model for analyzing transverse optical patterns including optical control and structural anisotropy. New Journal of Physics, 17, 083054.
• Gu, B., Kwong, N., & Binder, R. (2014). Quantum-confined strain gradient effect in semiconductor nanomembranes. Physical Review B, 90(19), 195208.
• Lewandowski, P., Ardizzone, V., Tse, Y. C., Kwong, N. H., Luk, M. H., Luecke, A., Abbarchi, M., Bloch, J., Baudin, E., Galopin, E., Lemaitre, A., Leung, P. T., Roussignol, P., Binder, R., Tignon, J., & Schumacher, S. (2014). Formation and Control of Transverse Patterns in a Quantum Fluid of Microcavity Polaritons. ULTRAFAST PHENOMENA AND NANOPHOTONICS XVIII, Proc. of SPIE, 8984, 89840X-1 - 89840X-8.
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  Transverse patterns in polariton fluids were recently studied as promising candidates for all-optical low-intensity switching. Here, we demonstrate these patterns in a specifically designed double-cavity system. We theoretically and experimentally analyse their formation and optical control. Our detailed theoretical analysis of the coupled nonlinear dynamics of the optical fields inside the double-cavity and the excitonic excitations inside the embedded semiconductor quantum wells is firmly based on a microscopic many-particle theory. Our calculations in the time domain enable us to study both the ultrafast transient dynamics of the patterns and their steady-state behavior under stationary excitation conditions. The patterns we report and analyze go beyond what can be observed and understood in a simple scalar quantum field. We find that polarization-selective excitation of the polaritons leads to a complex interplay between longitudinal-transverse splitting of the cavity modes and the spin-dependent interactions of the polaritons' excitonic component.
• Roberts, A. T., Binder, R., Kwong, N. H., Golla, D., Cormode, D., LeRoy, B. J., Everitt, H. O., & Sandhu, A. (2014). Optical Characterization of Electron-Phonon Interactions at the Saddle Point in Graphene. PHYSICAL REVIEW LETTERS, 112(18), 187401(5).
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  The role of many-body interactions is experimentally and theoretically investigated near the saddle point absorption peak of graphene. The time and energy-resolved differential optical transmission measurements reveal the dominant role played by electron-acoustic phonon coupling in band structure renormalization. Using a Born approximation for electron-phonon coupling and experimental estimates of the dynamic lattice temperature, we compute the differential transmission line shape. Comparing the numerical and experimental line shapes, we deduce the effective acoustic deformation potential to be D-eff(ac) similar or equal to 5 eV. This value is in accord with recent theoretical predictions but differs from those extracted using electrical transport measurements.
• Ardizzone, V., Lewandowski, P., Luk, M. H., Tse, Y. C., Kwong, N. H., Lücke, A., Abbarchi, M., Baudin, E., Galopin, E., Bloch, J., Lemaitre, A., Leung, P. T., Roussignol, P., Binder, R., Tignon, J., & Schumacher, S. (2013). Formation and control of Turing patterns in a coherent quantum fluid. Scientific Reports, 3.
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  PMID: 24145394;PMCID: PMC3804860;Abstract: Nonequilibrium patterns in open systems are ubiquitous in nature, with examples as diverse as desert sand dunes, animal coat patterns such as zebra stripes, or geographic patterns in parasitic insect populations. A theoretical foundation that explains the basic features of a large class of patterns was given by Turing in the context of chemical reactions and the biological process of morphogenesis. Analogs of Turing patterns have also been studied in optical systems where diffusion of matter is replaced by diffraction of light. The unique features of polaritons in semiconductor microcavities allow us to go one step further and to study Turing patterns in an interacting coherent quantum fluid. We demonstrate formation and control of these patterns. We also demonstrate the promise of these quantum Turing patterns for applications, such as low-intensity ultra-fast all-optical switches.
• Ardizzone, V., Lewandowski, P., Tse, Y. C., Kwong, N. H., Luk, M. H., Lucke, A., Abbarchi, M., Baudin, E., Bloch, J., Lemaitre, A., Leung, P. T., Roussignol, P., Binder, R., Tignon, J., & Schumacher, S. (2013). Formation and control of turing patterns from interacting polaritons in coupled semiconductor microcavities. CLEO: QELS_Fundamental Science, CLEO:QELS FS 2013, Qth4E.7.
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  Abstract: We report on the formation of hexagonal polariton patterns in double semiconductor microcavities operating in the OPO regime. We experimentally and theoretically demonstrate both the formation and the optical control of these patterns. © OSA 2013.
• Gu, B., Kwong, N. H., & Binder, R. (2013). Relation between the interband dipole and momentum matrix elements in semiconductors. Physical Review B - Condensed Matter and Materials Physics, 87(12).
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  Abstract: It is shown that a frequently used relation between the interband momentum and dipole matrix elements (shortened to the "p-r relation") in semiconductors acquires an additional correction term if applied to finite-volume crystals treated with periodic boundary conditions. The correction term, which is a generalization of the one obtained by Yafet for infinite crystals, does not vanish in the limit of infinite volume. We illustrate this with numerical examples for bulk GaAs and GaAs superlattices. The persistence of the correction term is traced to the subtle nature of the dipole matrix element with spatially extended wave functions. In contrast, a straightforward application of the findings by Blount and Haug [Theoretical Solid State Physics (Pergamon, Oxford, 1972)] yields the usual p-r relation in the distribution sense, without any corrections, when Bloch wave functions normalized to delta functions in crystal momentum space are used. Our findings therefore show that, for the interband dipole matrix element, using Bloch wave functions under periodic boundary conditions is not the proper way to approach the infinite-volume limit. From our numerical evaluations, we find that the correction term is large in the case of interband transitions in bulk GaAs, and that it can be chosen to be small in the case of intersubband transitions in superlattices, which are important in the context of terahertz (THz) radiation. We also show that one can interpret the infinite-volume p-r relation in terms of a limiting procedure using progressively broadened wave packet states that approach delta-normalized Bloch wave functions. Finally, we discuss the p-r relation for nanostructures in the envelope function approximation and show that the cell-envelope factorization of the nanostructure dipole matrix element into a cell-matrix element and an envelope overlap integral involves the cell gradient-k rather than the cell dipole matrix element. © 2013 American Physical Society.
• Luk, M. H., Tse, Y. C., Kwong, N. H., Leung, P. T., Lewandowski, P., Binder, R., & Schumacher, S. (2013). Transverse optical instability patterns in semiconductor microcavities: Polariton scattering and low-intensity all-optical switching. Physical Review B - Condensed Matter and Materials Physics, 87(20).
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  Abstract: We present a detailed theoretical study of transverse exciton-polariton patterns in semiconductor quantum well microcavities. These patterns are initiated by directional instabilities (driven mainly by polariton-polariton scattering) in the uniform pump-generated polariton field and are measured as optical patterns in a transverse plane in the far field. Based on a microscopic many-particle theory, we investigate the spatiotemporal dynamics of the formation, selection, and optical control of these patterns. An emphasis is placed on a previously proposed low-intensity, all-optical switching scheme designed to exploit these instability-driven patterns. Simulations and detailed analyses of simplified and more physically transparent models are used. Two aspects of the problem are studied in detail. First, we study the dependencies of the stability behaviors of various patterns, as well as transition time scales, on parameters relevant to the switching action. These parameters are the degree of built-in azimuthal anisotropy in the system and the switching (control) beam intensity. It is found that if the parameters are varied incrementally, the pattern system undergoes abrupt transitions at threshold parameter values, which are accompanied by multiple-stability and hysteresis behaviors. Moreover, during a real-time switching action, the transient dynamics of the system, in particular, the transition time scale, may depend significantly on the proximity of unstable patterns. The second aspect is a classification and detailed analysis of the polariton scattering processes contributing to the pattern dynamics, giving us an understanding of the selection and control of patterns as results of these processes' intricate interplay. The crucial role played by the (relative) phases of the polariton amplitudes in determining the gains and/or losses of polariton densities in various momentum modes is highlighted. As a result of this analysis, an interpretation of the actions of the various processes in terms of concepts commonly used in classical pattern-forming systems is given. © 2013 American Physical Society.
• Nguyen, D. T., Thapa, R., Rhonehouse, D., Zong, J., Miller, A., Hardesty, G., Kwong, N. H., Binder, R., & Chavez-Pirson, A. (2013). Towards all-fiber optical coolers using Tm-doped glass fibers. Proceedings of SPIE - The International Society for Optical Engineering, 8638.
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  Abstract: We present our experimental and theoretical results of optical cooling in Tm-doped glass fibers as optical cooler pumped by single-mode, high efficiency and high power Tm-doped glass fiber lasers. The effects of impurities including OHabsorption and transition metals have been investigated systematically using different purified glasses for fiber fabrication. Our experimental results of spectroscopic measurements show temperature drops of more than 30 degrees from room temperature with pump powers of less than 3W. The results are in good agreement with theoretical simulation. © 2013 SPIE.
• Verdenhalven, E., Binder, R., Knorr, A., & Malić, E. (2013). Derivation of the screened Bloch equations and application to carbon nanostructures. Chemical Physics, 413, 3-10.
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  Abstract: Optical properties of single-walled semiconducting and metallic carbon nanotubes are significantly influenced by excitonic effects. The excitonic binding energy strongly depends on Coulomb screening. Here, we show-using a non-perturbative single-time equation of motion method-how the momentum-dependent dielectric function (q) for carbon nanotubes can be consistently derived within a microscopic theory. We investigate the influence of the corresponding screening on the absorption spectra of semiconducting and metallic carbon nanotubes. We observe clearly smaller excitonic binding energies for metallic nanotubes arising from an efficient screening stemming from the crossing bands. The presented method can be applied in a straightforward way to calculate the Coulomb screening in other nanostructures, such as graphene and carbon nanoribbons. © 2012 Elsevier B.V. All rights reserved.
• Baijie, G. u., & Binder, R. (2012). Theoretical approach to the excitonic response of GaAs nanomembranes in the averaged-strain approximation. Journal of the Optical Society of America B: Optical Physics, 29(2), A60-A68.
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  Abstract: GaAs nanomembranes are thin crystalline GaAs semiconductor structures that can be bent or otherwise elastically deformed from their natural shape. We present a microscopic theory of the linear optical response of such deformed structures. Our approach combines conventional structural analysis (based on the theory of elasticity), the valence band Hamiltonians (Luttinger and Pikus-Bir) for III-V semiconductors, and the semiconductor Hamiltonian including Coulomb interaction. We formulate the general equation of motion for the interband polarization for thin elastically deformed nanomembranes. A simple limiting case results from the single-subband approximation and the averaged-strain approximation. Within this approximation scheme, we present numerical results for excitonic spectra for a cylindrically deformed membrane. © 2012 Optical Society of America.
• Luk, M. H., Tse, Y. C., Kwong, N. H., Leung, P. T., Schumacher, S., & Binder, R. (2012). All-optical control of transverse patterns in planar semiconductor microcavities. 2012 Conference on Lasers and Electro-Optics, CLEO 2012.
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  Abstract: We analyze the selection/switching of instability-induced optical patterns in semiconductor microcavities. Besides realistic calculations, we use a population model and Catastrophe theory to organize our understanding of the patterns' dynamics. © 2012 OSA.
• Luk, M. H., Tse, Y. C., Kwong, N. H., Leung, P. T., Schumacher, S., & Binder, R. (2012). All-optical control of transverse patterns in planar semiconductor microcavities. CLEO: Applications and Technology, CLEO_AT 2012, JW4A.41.
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  Abstract: We analyze the selection/switching of instability-induced optical patterns in semiconductor microcavities. Besides realistic calculations, we use a population model and Catastrophe theory to organize our understanding of the patterns' dynamics. © 2012 Optical Society of America.
• Luk, M. H., Tse, Y. C., Kwong, N. H., Leung, P. T., Schumacher, S., & Binder, R. (2012). All-optical control of transverse patterns in planar semiconductor microcavities. CLEO: Science and Innovations, CLEO_SI 2012, JW4A.41.
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  Abstract: We analyze the selection/switching of instability-induced optical patterns in semiconductor microcavities. Besides realistic calculations, we use a population model and Catastrophe theory to organize our understanding of the patterns' dynamics. © 2012 Optical Society of America.
• Luk, M. H., Tse, Y. C., Kwong, N. H., Leung, P. T., Schumacher, S., & Binder, R. (2012). All-optical control of transverse patterns in planar semiconductor microcavities. Optics InfoBase Conference Papers.
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  Abstract: We analyze the selection/switching of instability-induced optical patterns in semiconductor microcavities. Besides realistic calculations, we use a population model and Catastrophe theory to organize our understanding of the patterns' dynamics. © 2012 Optical Society of America.
• Nguyen, D. T., Zong, J., Rhonehouse, D., Miller, A., Yao, Z., Hardesty, G., Kwong, N. H., Binder, R., & Chavez-Pirson, A. (2012). All fiber approach to solid-state laser cooling. Proceedings of SPIE - The International Society for Optical Engineering, 8275.
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  Abstract: An all fiber approach to optical cooling is being investigated experimentally and theoretically using Tm-doped fiber laser and Tm-doped fiber cooler. A single mode, high efficiency and high power Tm-doped fiber laser is used to pump at the absorption edge of Tm-doped fiber coolers, one made by germanate and the other by tellurite glasses. The glass characterization shows that the quenching effect, which is negative for cooling processes in the fiber, in germanate glass is much stronger than that in tellurite glass. The preliminary results of experiments indicate cooling effects could occur in the fiber, but net cooling in the system has not been achieved. A theoretical framework aimed at understanding the nature of cooling in this laser cooling system has been developed which shows that the temperature in the sample could increase even if the fiber core is indeed cooling. The details of the temperature dynamics depend on many factors such as background loss and absorption of scattered light by the heat spreader. © 2012 SPIE.
• Nguyen, D. T., Shanor, C., Zong, J., Tian, W., Yao, Z., Jianfeng, W. u., Weiss, J., Binder, R., & Chavez-Pirson, A. (2011). Conceptual study of a fiber-optical approach to solid-state laser cooling. Proceedings of SPIE - The International Society for Optical Engineering, 7951.
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  Abstract: Optical cooling in an all fiber system using fiber laser pumps and cooling fibers doped with rare earth ions has been investigated both theoretically and experimentally. A 2% Tm doped germanate glass was selected from glasses with different Tm concentrations 0.5, 1, 2, 3, 4, 5, 6, 8 and 10% wt for fabrication of the cooling fiber. A high efficiency, single mode Tm-doped fiber laser has been built to pump a Tm-doped fiber cooler. The cooling experiments done in a vacuum chamber show indications that cooling has occurred in the fiber. A theoretical framework to understand the nature of cooling in this laser cooling system has been developed which highlights the cooling power available as a function of various material and fiber parameters including background loss and absorption saturation effects in the cooling fiber. Cooling characteristics, with special emphasis on the fiber's saturation behavior, have been studied using theoretical models of Tm3+-doped glass (4-level models) and Tm3+ doped KLa(WO4)2 crystals (20-level model). © 2010 SPIE.
• Gu, B., Kwong, N. H., Binder, R., & Smirl, A. L. (2010). Slow and fast light associated with polariton interference. Physical Review B - Condensed Matter and Materials Physics, 82(3).
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  Abstract: Propagation times of optical pulses through a medium near an absorptive resonance with and without spatial dispersion are studied and contrasted. When spatial dispersion is not present, a light pulse is expected to traverse a medium in a time inversely proportional to its group velocity. In a medium with spatial dispersion, where two polariton modes exist (here, bulk GaAs as an example), a similar description is obtained if the losses are such that light propagates primarily in one mode. However, we show that, when the broadening of the resonance (dephasing rate) is below a critical value, a frequency range exists near resonance where the transit times are determined by interference between copropagating polaritons and deviate strongly from expectations based on the group velocities of the polariton branches. When the interference is constructive at the samples end face, the transit times are determined by the average of the inverse group velocities; when it is destructive, we find abrupt transitions between very slow (long positive) and very fast (large negative) transit times. We present quantitative criteria for the resolution of these features and for distortion-free propagation in the spectral vicinity of them. Our analysis puts the well-known slow- and fast-light effects in systems without spatial dispersion into a broader context by illustrating that they are a limiting case of systems with spatial dispersion. © 2010 The American Physical Society.
• M., A., Gauthier, D. J., Schumacher, S., Kwong, N. H., Binder, R., & Smirl, A. L. (2010). Transverse optical patterns for ultra-low-light-level all-optical switching. Laser and Photonics Reviews, 4(2), 221-243.
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  Abstract: We review recent theoretical and experimental efforts toward developing an all-optical switch based on transverse optical patterns. Transverse optical patterns are formed when counterpropagating laser beams interact with a nonlinear medium. A perturbation, in the form of a weak switch beam injected into the nonlinear medium, controls the orientation of the generated patterns. Each state of the pattern orientation is associated with a state of the switch. That is, information is stored in the orientation state. A realization of this switch using a warm rubidium vapor shows that it can be actuated by as few as 600±40 photons with a response time of 5μs. Models of non-linear optical interactions in semiconductor quantum wells and microresonators suggest these systems are also suitable for use as fast all-optical switches using this same conceptual design, albeit at higher switching powers. © 2010 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
• Rupper, G., Kwong, N. H., & Binder, R. (2010). Theory of time-resolved photo-luminescence and carrier lifetime measurements in GaAs/GaInP heterostructures. Proceedings of SPIE - The International Society for Optical Engineering, 7614.
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  Abstract: Recently, interest in optical refrigeration of semiconductors, which is based on photo-luminescence up-conversion, has drawn extensive attention both theoretically and experimentally. Theoretical descriptions often treat spatially homogeneous semiconductors, because of their conceptual simplicity. In typical experiments, however, semiconductors are usually heterostructures designed to reduce non-radiative recombination at the sample's surface. In particular, GaAs/GaInP structures have been used in experiments. In these structures, the GaAs layers are usually unintentionally p-doped, while the surface layers of GaInP are n-doped. Recent measurements of the non-radiative recombiation lifetime yielded values in the desirable inverse microsecond regime, and it is believed that the non-radiative recombination processes occur mainly at the heterostructure interfaces and its surfaces. For this reason, it is important to know the spatial density distribution of the excited carriers. Furthermore, photo-luminescence and carrier lifetime measurements are not spatially resolved, and therefore it is desirable to have a theory that can simulate lifetime measurements using the spatially varying density profile as an input. We have developed such a theory, using the simplifying assumption of quasi-thermal equilibrium (at each time during the photo-luminescence decay process). Using this theory, we are able to relate measurable (i.e. spatially averaged) lifetime measurements to the underlying non-radiative decay processes that, in our simulations, occur predominantly at the GaAs/GaInP interface. From this, we find that spatial inhomogeneities in the carrier density, which are most pronounced at low optical excitation powers, can have appreciable effects on the interpretation of the lifetime measurements. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Rupper, G., Kwong, N. H., Binder, R., Li, C., & Sheik-Bahae, M. (2010). Effect of n-p-n heterostructures on interface recombination and semiconductor laser cooling. Journal of Applied Physics, 108(11).
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  Abstract: The design of doped n-p-n semiconductor heterostructures has a significant influence on the structures' nonradiative decay and can also affect their photoluminescence characteristics. Such structures have recently been explored in the context of semiconductor laser cooling. We present a theoretical analysis of optically excited n-p-n structures, focusing mainly on the influence of the layer thicknesses and doping concentrations on nonradiative interface recombination. We find that high levels of n-doping (1019 cm-3) can reduce the minority-carrier density at the interface and increase the nonradiative lifetime. We calculate time-dependent luminescence decay and find them to be in good agreement with experiment for temperatures >120 K, which is the temperature range in which our model assumptions are expected to be valid. A theoretical analysis of the cooling characteristics of n-p-n structures elucidates the interplay of nonradiative, radiative, and Auger recombination processes. We show that at high optical excitation densities, which are necessary for cooling, the undesired nonradiative interface recombination rates for moderate (1017 cm-3) n-doping concentrations are drastically increased, which may be a major hindrance in the observation of laser cooling of semiconductors. On the other hand, high n-doping concentrations are found to alleviate the problem of increased nonradiative rates at high excitation densities, and for the model parameters used in the calculation we find positive cooling efficiencies over a wide range of excitation densities. © 2010 American Institute of Physics.
• Binder, R. (2009). Four-wave mixing and many-particle effects in semiconductors. 2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum Electronics and Laser Science Conference, CLEO/QELS 2009.
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  Abstract: Four-wave mixing in semiconductor quantum wells has long been used to investigate many-particle effects. We introduce the theoretical concepts and illustrate some developments of the field, which D.S. Chemla helped to shape. ©2009 Optical Society of America.
• Binder, R. (2009). Four-wave mixing and many-particle effects in semiconductors. Optics InfoBase Conference Papers.
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  Abstract: Four-wave mixing in semiconductor quantum wells has long been used to investigate many-particle effects. We introduce the theoretical concepts and illustrate some developments of the field, which D.S. Chemla helped to shape. © 2009 Optical Society of America.
• Gu, B., Kwong, N. H., Binder, R., & Smirl, A. L. (2009). Interference-induced slow and fast light in bulk semiconductors. 2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum Electronics and Laser Science Conference, CLEO/QELS 2009.
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  Abstract: The interference between the two exciton polaritons in semiconductors is predicted to give a time delay for traversing light pulses that is unrelated to the polaritons' group velocities. ©2009 Optical Society of America.
• Gu, B., Kwong, N. H., Binder, R., & Smirl, A. L. (2009). Interference-induced slow and fast light in bulk semiconductors. Optics InfoBase Conference Papers.
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  Abstract: The interference between the two exciton polaritons in semiconductors is predicted to give a time delay for traversing light pulses that is unrelated to the polaritons' group velocities. © 2009 Optical Society of America.
• Kwong, N. H., Rupper, G., & Binder, R. (2009). Self-consistent T-matrix theory of semiconductor light-absorption and luminescence. Physical Review B - Condensed Matter and Materials Physics, 79(15).
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  Abstract: We present a detailed theoretical analysis of light-absorption and luminescence of bulk semiconductors at finite electron-hole densities and temperatures. The analysis is carried out within a real-time Green's-function formalism with self-energies evaluated in the self-consistent T-matrix approximation. The theory is applied to a two-band model of GaAs, for which the single-particle self-energies and spectral functions and the absorption and luminescence spectra are calculated. The effects of excitonic correlations on these quantities are highlighted. © 2009 The American Physical Society.
• Kwong, N. H., Schumacher, S., & Binder, R. (2009). Electron-spin beat susceptibility of excitons in semiconductor quantum wells. Physical Review Letters, 103(5).
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  Abstract: Recent time-resolved differential transmission and Faraday rotation measurements of long-lived electron-spin coherence in quantum wells displayed intriguing parametric dependencies. For their understanding we formulate a microscopic theory of the optical response of a gas of optically incoherent excitons whose constituent electrons retain spin coherence, under a weak magnetic field applied in the quantum well's plane. We define a spin beat susceptibility and evaluate it in linear order of the exciton density. Our results explain the many-body physics underlying the basic features observed in the experimental measurements. © 2009 The American Physical Society.
• Rupper, G., Kwong, N. H., & Binder, R. (2009). Microscopic Theory of Luminescence and its Application to the Optical Refrigeration of Semiconductors. Optical Refrigeration: Science and Applications of Laser Cooling of Solids, 139-167.
• Rupper, G., Kwong, N. H., & Binder, R. (2009). The role of finite spatial beam profiles on photo-luminescence and laser cooling in GaAs structures. Proceedings of SPIE - The International Society for Optical Engineering, 7228.
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  Abstract: We present a microscopic many-body theory of optical refrigeration of semiconductors with finite spatial beam profile extension. The theory is an extension of our previous theory of optical refrigeration of GaAs, which had been limited to spatially homogeneous systems. In it, optically excited electron-hole pairs can be an unbound pairs, or pairs bound by the attractive Coulomb interaction (excitons). Assuming the electron-hole pairs to be in quasi-thermal equilibrium, our theory calculates its absorption and luminescence spectra within a diagrammatic (real-time) Green's function approach at the selg-consistent T-matrix level. The present extension to lateral spatial inhomogeneities due to finite beam spot size utilizes a photon transport equation which is based on a diagrammatic formulation of finite beam spot size utilizes a photon transport equation which is based on a for simplicity, and analytical solution for the pair density and power density rate equations is obtained, and numerical self-consistent solutions are presented. The result show that for typical beam waist parameters, lateral (radial) photon transport does not significantly impede the theoretically predicted cooling process. © 2009 SPIE.
• Schumacher, S., Kwong, N. H., Binder, R., & Smir, A. L. (2009). Low intensity directional switching of light in semiconductor microcavities. Physica Status Solidi - Rapid Research Letters, 3(1), 10-12.
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  Abstract: Recently it was demonstrated that in atomic vapors weak control beams can manipulate (or switch) the propagation direction of strong light beams [Dawes et al., Science 308, 672 (2005)]. As a semiconductor analog of such all-optical switching, we present a proposal for similar manipulation and switching in planar semiconductor microcavities. Using a microscopic many-particle theory, we investigate the spatiotemporal dynamics of four-wave mixing signals and related instabilities in these systems. Even though the underlying physical processes are different from atomic systems, we find that microcavities allow for reversible directional manipulation of light. © 2009 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim.
• Schumacher, S., Kwong, N. H., Binder, R., & Smirl, A. L. (2009). Optical instabilities in semiconductor quantum-well systems driven by phase-space filling. Physica Status Solidi (B) Basic Research, 246(2), 307-310.
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  Abstract: Four-wave mixing (FWM) is one of the best known phenomena in semiconductor optics. Recent experimental results of FWM instabilities and optical switching in atomic systems have renewed the interest in FWM and possible related instabilities in semiconductors. We have recently performed theoretical investigations of FWM instabilities in a variety of semiconductor quantum well systems (single quantum wells, Bragg-spaced multiple quantum wells, and planar semiconductor micocavities) and shown that different systems require different physical processes that potentially can give rise to FWM instabilities. In this contribution, we concentrate on the simple (and largely academic) finding that phase-space filling together with spatial exciton dispersion can lead to FWM instabilities in single quantum wells. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.
• Rupper, G., Kwong, N. H., Gu, B., & Binder, R. (2008). Theory of laser cooling of semiconductor quantum wells. Physica Status Solidi (B) Basic Research, 245(6), 1049-1054.
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  Abstract: We present a microscopic many-body theory of laser cooling of semiconductor quantum wells. The cooling mechanism is the upconversion of pump photons through absorption and subsequent luminescence by an electron-hole-exciton mixture maintained at steady state in the quantum well. Assuming this Coulomb plasma to be in quasi-thermal equilibrium, our theory calculates its absorption/luminescence spectra within a diagrammatic (real-time) Green's function approach at the self-consistent T-matrix level. These spectra are used in a cooling threshold analysis for GaAs quantum wells that also takes into account other losses into heat. We compare the present results with previous ones obtained for bulk GaAs. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
• Rupper, G., Kwong, N. H., Gu, B., & Binder, R. (2008). Theory of luminescence and optical refrigeration in p-doped semiconductors. Proceedings of SPIE - The International Society for Optical Engineering, 6907.
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  Abstract: We present a microscopic many-body theory of optical refrigeration of p-doped semiconductors. Conceptually, the refrigeration mechanism is the upconversion of pump photons through absorption and subsequent luminescence by electron-hole pairs. The electron-hole pair can be an unbound pair, a pair bound by the attractive Coulomb interation (exciton), or a pair in which the hole is located at an acceptor site. Assuming the electron-hole pairs to be in quasi-thermal equilibrium, our theory calculates its absorption and luminescence spectra within a diagrammatic (real-time) Green's function approach at the self-consistent T-matrix level. The strong on-site Coulomb repulsion of holes at acceptor sites is taken into account via a truncation of the acceptor Fock space, which excludes states with higher than single-hole occupation. The resulting absorption and luminescence spectra are used in a cooling threshold analysis for GaAs that also takes into account other losses into heat. We compare the present results for p-doped GaAs with previous ones obtained for undoped GaAs.
• Schumacher, S., Kwong, N. H., & Binder, R. (2008). All-optical signal amplification in multiple-quantum-well resonant photonic bandgap structures. Applied Physics Letters, 92(13).
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  Abstract: Using a microscopic many-particle theory, we predict all-optical amplification of low-intensity light pulses in resonant photonic bandgap structures realized by Bragg-spaced semiconductor multiple quantum wells. The discussed scheme is based on mirrorless parametric amplification. © 2008 American Institute of Physics.
• Schumacher, S., Kwong, N. H., & Binder, R. (2008). Large optical gain from four-wave mixing instabilities in semiconductor quantum wells. EPL, 81(2).
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  Abstract: Based on a microscopic many-particle theory, we predict large optical gain in the probe and background-free four-wave mixing directions caused by excitonic instabilities in semiconductor quantum wells. For a single quantum well with radiative-decay limited dephasing in a typical pump-probe setup we discuss the microscopic driving mechanisms and polarization and frequency dependence of these instabilities. © Europhysics Letters Association.
• Schumacher, S., Kwong, N. H., Binder, R., & Smirl, A. L. (2008). Instability induced all-optical switching in planar semiconductor microcavities. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series.
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  Abstract: Using a microscopic theory, we predict all-optical switching in planar semiconductor microcavities where a weak beam switches a stronger signal. The scheme is similar to that recently demonstrated in atomic vapors [Dawes et al., Science 308, 672 (2005)]. © 2008 Optical Society of America.
• Kwong, N. H., Nguyen, D. T., Binder, R., & Smirl, A. L. (2007). Polarization-dependence of ultrafast optical nonlinearities of Bragg-spaced quantum wells. Conference on Lasers and Electro-Optics, 2007, CLEO 2007.
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  Abstract: We present a microscopic theory for the polarization dependence of the nonlinear reflection of Bragg-spaced quantum wells. Our theory includes polariton correlations beyond third order. Comparisons with experimental results show reasonably good agreement. © 2006 Optical Society of America.
• Kwong, N. H., Nguyen, D. T., Binder, R., & Smirl, A. L. (2007). Polarization-dependence of ultrafast optical nonlinearities of Bragg-spaced quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series.
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  Abstract: We present a microscopic theory for the polarization dependence of the nonlinear reflection of Bragg-spaced quantum wells. Our theory includes polariton correlations beyond third order. Comparisons with experimental results show reasonably good agreement. ©2006 Optical Society of America.
• Kwong, N. H., Rupper, G., Gu, B., & Binder, R. (2007). The relation between light absorption and luminescence in laser cooling of two-dimensional semiconductor systems. Proceedings of SPIE - The International Society for Optical Engineering, 6461.
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  Abstract: In efforts underway to achieve laser cooling of semiconductors, an electron-hole population is generated in the sample and maintained in a steady state. The analysis of light absorption by and luminescence from this population is basic to the understanding of feasibility and efficiency issues of the cooling process. It is commonly understood that, when this electron-hole plasma is in quasi-thermal equilibrium (equilibrium at a fixed density), the KMS (Kubo-Martin-Scliwinger) relation holds between its luminescence and absorption spectra: their ratio is proportional to the Bose distribution function characterized by the temperature and chemical potential of the plasma. The proportionality factor, which affects the total luminescence rate, may generally depend on the dimensionality and geometry of the system, In this Contribution, as a preliminary step to extend our theoretical analysis of semiconductor cooling to quantum well systems, we discuss the application of the KMS relation to their spectra. In particular, we derive and discuss the geometrical proportionality factor in the KMS relation forquantum wells and compare it to its counterpart for bulk semiconductors.
• Kwong, N. H., Schumacher, S., & Binder, R. (2007). Electron spin beat nonlinear susceptibility in semiconductor quantum wells. Conference on Lasers and Electro-Optics, 2007, CLEO 2007.
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  Abstract: We present, a comprehensive theory of optically probing electron spin precession in low-density quantum well exciton populations. We trace the microscopic origins of fiatures observed in differential transmission and Faraday rotation measurements to exciton interactions. © 2007 Optical Society of America.
• Kwong, N. H., Schumacher, S., & Binder, R. (2007). Electron spin beat nonlinear susceptibility in semiconductor quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series.
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  Abstract: We present a comprehensive theory of optically probing electron spin precession in low-density quantum well exciton populations. We trace the microscopic origins of features observed in differential transmission and Faraday rotation measurements to exciton interactions. ©2007 Optical Society of America.
• Nguyen, D. T., Kwong, N. H., Yang, Z. S., Binder, R., & Smirl, A. L. (2007). Mechanism of all-optical spin-dependent polarization switching in Bragg-spaced quantum wells. Applied Physics Letters, 90(18).
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  Abstract: The authors outline a microscopic theory of pump-induced anisotropy in the optical response of Bragg-spaced quantum wells (BSQWs). Their theory explains the manipulation of the band structure of the BSQWs by the pump through the microscopic interactions between excitons in the quantum wells. They apply their theory to understand the mechanism of an all-optical polarization switch implemented on a BSQW structure. They trace the relation between the strongly spin-dependent exciton-exciton interactions and the switching signal. Reasonably good agreement is found between their theoretical results and experimental data. © 2007 American Institute of Physics.
• Rupper, G., Kwong, N. H., & Binder, R. (2007). Optical refrigeration of GaAs: Theoretical study. Physical Review B - Condensed Matter and Materials Physics, 76(24).
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  Abstract: We have performed a theoretical analysis of laser cooling (i.e., cooling via luminescence up-conversion) of bulk GaAs based on a microscopic many-particle theory of absorption and luminescence of a partially ionized electron-hole plasma. This theory allows us to model the semiconductor over a wide range of densities and for temperatures from the few-Kelvin regime to above room temperature. In this paper, we analyze in detail how various physical processes help or hinder cooling. We show that at high temperatures (T≥300 K), cooling is limited by Auger recombination. As temperature is lowered to about 200 K, band filling as well as excitonic effects become significant. Phase-space filling hinders cooling but is overcompensated by excitonic effects, which are found to be beneficial for cooling. At very low temperatures (≤30 K), parasitic background absorption limits cooling, and the interplay between excitonic absorption line shapes and parasitic background absorption determines whether or not cooling is possible in this temperature regime. © 2007 The American Physical Society.
• Rupper, G., Kwong, N. H., & Binder, R. (2007). Theory of optical refrigeration in p-doped semiconductors. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series.
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  Abstract: We present a microscopic theory for luminescence of doped GaAs and its application to a study of optical refrigeration. We find that p-doping affects the temperature dependence of the cooling threshold in a complex way. ©2006 Optical Society of America.
• Schumacher, S., Kwong, N. H., & Binder, R. (2007). Influence of exciton-exciton correlations on the polarization characteristics of polariton amplification in semiconductor microcavities. Physical Review B - Condensed Matter and Materials Physics, 76(24).
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  Abstract: Based on a microscopic many-particle theory, we investigate the influence of excitonic correlations on the vectorial polarization state characteristics of the parametric amplification of polaritons in semiconductor microcavities. We study a microcavity with perfect in-plane isotropy. A linear stability analysis of the cavity-polariton dynamics shows that in the co-linear (TE-TE or TM-TM) pump-probe polarization state configuration, excitonic correlations diminish the parametric scattering process, whereas it is enhanced by excitonic correlations in the cross-linear (TE-TM or TM-TE) configuration. Without any free parameters, our microscopic theory gives a quantitative understanding how many-particle effects can lead to a rotation or change of the outgoing (amplified) probe signal's vectorial polarization state relative to the incoming one's. © 2007 The American Physical Society.
• Schumacher, S., Kwong, N. H., Binder, R., & Smirl, A. L. (2007). Theory of optical gain from four-wave mixing instabilities in quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series.
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  Abstract: We predict that in a typical pump-probe setup four-wave mixing instabilities associated with biexcitonic correlations in a single semiconductor quantum well can yield large optical gain in the probe and background-free four-wave mixing directions. ©2007 Optical Society of America.
• Yang, Z., Sipe, J. E., Kwong, N. H., Binder, R., & Smirl, A. L. (2007). Antireflection coating for quantum-well Bragg structures. Journal of the Optical Society of America B: Optical Physics, 24(8), 2013-2022.
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  Abstract: We develop a strategy to reduce large reflection losses from quantum-well Bragg structures through an anti-reflection coating technique. It is based on generalized refractive indices, which we call "effective coupling indices" (ECIs), that can be introduced to describe the coupling of light into quantum-well Bragg structures. For the example of a spectrally narrow band, which is relevant for slow-light applications, we clarify the dependence of the ECIs on the spectral bandwidth and discuss the relation between the ECIs and the group-velocity index. Numerical simulations of reflection spectra demonstrate the effectiveness of the ECI concept. © 2007 Optical Society of America.
• Binder, R., & Lindberg, M. (2006). Optical electron-hole tweezers in semiconductors. Journal of Physics Condensed Matter, 18(2), 729-740.
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  Abstract: The theory of transversal light forces on electron-hole pairs in semiconductors has been formulated recently (Lindberg and Binder 2003 J. Phys.: Condens. Matter 15 1119), but only light forces from single Gaussian beams were considered. In the present paper, it is shown theoretically that Hermite-Gaussian beams can be used to reduce and even reverse natural wavepacket spreading. Furthermore, a spatially moving beam can be used to displace and accelerate an electron-hole plasma, in analogy to well-known optical tweezers in atomic systems. The light forces exerted by Hermite-Gaussian beams appear to be robust and therefore of possible practical importance. © 2006 IOP Publishing Ltd.
• Binder, R., Yang, Z. S., Kwong, N. H., Nguyen, D. T., & Smirl, A. L. (2006). Light pulse delay in semiconductor quantum well Bragg structures. Physica Status Solidi (B) Basic Research, 243(10), 2379-2383.
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  Abstract: We discuss a scheme for controlled stopping, storing, and releasing of light pulses in one-dimensional resonant photonic band gap structures (RPBG's) made of Bragg spaced quantum wells. Our scheme is based on parametric manipulation of the RPBG's bandstructure in real time. We extend earlier studies on the limitations of presently existing quantum well Bragg structures to the regime of small detunings of the exciton resonance from the Bragg frequency. We also set the stage for exploring mechanisms of bandstructure control by studying the nonlinear response of the quantum well RPBG. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA,.
• Kwong, N. H., & Binder, R. (2006). Theory of electron spin coherence in differential transmission measurements on semiconductor quantum wells. Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, CLEO/QELS 2006.
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  Abstract: We present a microscopic interpretation of recent differential transmission measurements of electron spin coherence in GaAs quantum wells. We show that certain unexpected features in the beat signal can reveal finer characteristics of excitonic correlations. © 2006 Optical Society of America.
• Kwong, N. H., Yang, Z. S., Nguyen, D. T., Binder, R., & Smirl, A. L. (2006). Light pulse delay in semiconductor quantum well Bragg structures. Proceedings of SPIE - The International Society for Optical Engineering, 6130.
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  Abstract: We present a theoretical analysis of light pulse delay in resonant photonic bandgap structures made from Bragg-spaced semiconductor quantum wells. Quantum well Bragg structures offer the possibility for parametric manipulation of the polariton band structure. This, in turn, may be used for stopping, storing, and releasing of light pulses. Based on a theoretical model utilizing a time-dependent transfer matrix approach to the solution of Maxwell's equations, we study light pulse propagation, light pulse trapping and releasing, and light pulse deformation in these structures. We discuss the photonic band structure concepts relevant to our light delay scheme and present numerical simulation results of pulse delay through presently existing quantum well Bragg structures.
• Nguyen, D. T., Kwong, N. H., Binder, R., & Smirl, A. L. (2006). Theory of ultrafast optical gain in the nonlinear reflectivity of semiconductor bragg structures. Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, CLEO/QELS 2006.
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  Abstract: We present a microscopic theory for the nonlinear reflection of semiconductor Bragg structures. Our theoretical results showing ultrafast optical gain complement recent experimental observations and allow for the identification of the underlying many-particle processes. © 2006 Optical Society of America.
• Rupper, G., Kwong, N. H., & Binder, R. (2006). Large excitonic enhancement of optical refrigeration in semiconductors. Physical Review Letters, 97(11).
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  Abstract: We present a theoretical analysis for laser cooling of bulk GaAs based on a microscopic many-particle theory of absorption and luminescence of a partially ionized electron-hole plasma. Our cooling threshold analysis shows that, at low temperatures, the presence of the excitonic resonance in the luminescence is essential in competing against heating losses. The theory includes self-consistent energy renormalizations and line broadenings from both instantaneous mean-field and frequency-dependent carrier-carrier correlations, and it is applicable from the few-Kelvin regime to above room temperature. © 2006 The American Physical Society.
• Rupper, G., Kwong, N. H., & Binder, R. (2006). Theory of semiconductor laser cooling at low temperatures. Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, CLEO/QELS 2006.
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  Abstract: We present a comprehensive many-particle theory for optical refrigeration of bulk GaAs via luminescence up-conversion. We predict cooling in the regime of a partially ionized exciton gas and discuss its temperature dependence. © 2006 Optical Society of America.
• Rupper, G., Kwong, N. H., & Binder, R. (2006). Theory of semiconductor laser cooling at low temperatures. Physica Status Solidi (C) Current Topics in Solid State Physics, 3(7), 2489-2493.
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  Abstract: We present a microscopic many-body theory of laser cooling of semiconductors. Using a standard diagrammatic Green's function approach, we calculate the absorption/luminescence spectra of a partially ionized electron-hole plasma in quasi-equilibrium at the self-consistent T-matrix level. This theory is applied to studying criteria of cooling threshold and efficiency in bulk GaAs, focusing mainly on the temperature range between 5 K and 100 K. In particular, we discuss the transition from the high temperature regime dominated by absorption in the e-h continuum to the low temperature regime dominated by resonant exciton absorption. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.
• Rupper, G., Kwong, N. H., & Binder, R. (2006). Theory of semiconductor laser cooling at low temperatures. Proceedings of SPIE - The International Society for Optical Engineering, 6115.
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  Abstract: On the road toward experimental realization of laser-induced cooling of semiconductors, theoretical investigations are necessary for a detailed understanding of the microscopic phenomena underlying the cooling process, and for a prediction of optimal parameter regimes where efficient cooling could be expected. A recent realistic theory for cooling of bulk GaAs by Sheik-Bahae and Epstein has focused on the high-temperature regime, where the cooling process involves absorption of and luminescence from an electron-hole plasma. Using a microscopic many-particle theory, we extend the Sheik-Bahae Epstein approach to the low-temperature regime, where excitonic effects, i.e. effects of bound electron hole pairs in quasi-thermal equilibrium with correlated unbound pairs (i.e. the plasma) become important. We use a diagrammatic approach that is non-perturbative in the Coulomb interaction and contains effects of phase-space filling, single-particle renormalization in a partially ionized plasma, and screening. We ensure that our theory contains the relevant limiting cases for (partial) ionization in the low-density regime (Saha equation and Beth-Uhlenbeck formula) as well as the high density regime (Mott transition). Based on our microscopic theory for absorption and luminescence in the quasi-thermal equilibrium regime, we present a detailed study of cooling criteria at low temperature, focusing mainly on the temperature regime between 5K and 100K. In particular, we discuss the transition from the high temperature regime dominated by absorption in the e-h continuum to the low-temperature regime dominated by resonant exciton absorption.
• Kwong, N. H., Binder, R., Sarkar, S., Palinginis, P., & Wang, H. (2005). Theory of inducing electron spin coherence without spin precession in GaAs quantum well waveguides. Quantum Electronics and Laser Science Conference (QELS), 3, 1914-1916.
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  Abstract: We present a theory for a differential transmission experiment that generated electron spin coherence in quantum well waveguides without DC magnetic fields. We show how optical selection rules explain the spin coherence's creation and detection. © 2004 Optical Society of America.
• Kwong, N. H., Rumyantsev, I., Binder, R., & Smirl, A. L. (2005). Relation between phenomenological few-level models and microscopic theories of the nonlinear optical response of semiconductor quantum wells. Physical Review B - Condensed Matter and Materials Physics, 72(23).
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  Abstract: We analyze a generic atomic few-level model for the third-order (χ(3)) optical response of semiconductor quantum wells. The purpose is to seek a good understanding of the physical nature of the model's parameters in terms of the material's microscopic constituents and their motions. The strategy is to bring the algebraic expression of the χ(3) interband polarization in the few-level model to a form similar to that derived in microscopic theories. Most importantly, in the coherent limit, we make the "time evolution structure" of the interband polarization in the few-level and microscopic formalisms coincide, whereby the atomic model's parameters can be interpreted microscopically through a comparison of terms of similar structure in the two formalisms. We also discuss how the conclusion of this comparison can be changed by the introduction of phenomenological dephasing and decay into both theories. © 2005 The American Physical Society.
• Sarkar, S. K., Palinginis, P., Wang, H., Ku, P., Chang-Hasnain, C. J., Kwong, N. H., & Binder, R. (2005). Inducing electron spin coherence in GaAs quantum well waveguides: Spin Coherence without spin precession. Quantum Electronics and Laser Science Conference (QELS), 1, 601-603.
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  Abstract: Electron spin coherence is induced via light-hole transitions in a quantum well waveguide without a DC magnetic field. The spin coherence is detected through effects of quantum interference in spectral domain nonlinear optical response. © 2005 Optical Society of America.
• Sarkar, S., Palinginis, P., Ku, P., Chang-Hasnain, C. J., Kwong, N. H., Binder, R., & Wang, H. (2005). Inducing electron spin coherence in GaAs quantum well waveguides: Spin coherence without spin precession. Physical Review B - Condensed Matter and Materials Physics, 72(3).
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  Abstract: We demonstrate the generation and detection of electron spin coherence in a quantum well waveguide without either an external or internal dc magnetic field. In the absence of spin precession, the induced spin coherence is detected through effects of quantum interference in the spectral domain coherent nonlinear optical response. We interpret the experimental results qualitatively using a few-level model with optical selection rules as its basic ingredient. © 2005 The American Physical Society.
• Yang, Z. S., Kwong, N. H., Binder, R., & Smirl, A. L. (2005). Distortionless light pulse delay in quantum-well Bragg structures. Optics Letters, 30(20), 2790-2792.
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  PMID: 16252776;Abstract: We describe a reflection scheme that allows Bragg-spaced semiconductor quantum wells to be used to trap, store, and release light. We study the temporal and spectral distortion of delayed light pulses and show that this geometry allows multibit delays and offers a high degree of distortion compensation. © 2005 Optical Society of America.
• Yang, Z. S., Kwong, N. H., Binder, R., & Smirl, A. L. (2005). Stopping, storing and releasing light in quantum well Bragg structures. Quantum Electronics and Laser Science Conference (QELS), 3, 1871-1873.
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  Abstract: Stopping, storing and releasing of light in resonant photonic bandgap structures made from Bragg-spaced quantum wells is studied. The expected performance of almost ideal infinite systems is contrasted with that of existing structures. © 2005 Optical Society of America.
• Yang, Z. S., Kwong, N. H., Binder, R., & Smirl, A. L. (2005). Stopping, storing, and releasing light in quantum-well Bragg structures. Journal of the Optical Society of America B: Optical Physics, 22(10), 2144-2156.
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  Abstract: We present a theoretical analysis of light propagation in one-dimensional resonant photonic bandgap structures (RPBGs). The analysis is aimed at evaluating the feasibility of controlled stopping, storing, and releasing of light pulses by parametric manipulation of the RPBG's andstructure. First we lay the conceptual foundation of light-pulse delay by means of band structure control in infinite RPBGs, and then we contrast the idealized concepts with numerical results for realistic, finite-sized RPBGs. For a physical model for RPBGs, we use semiconductor quantum-well Bragg structures, but the general analysis is valid for a wider class of RPBG. We show that the usefulness of RPBGs for optical delay lines depends critically on the number of quantum wells and the dephasing and loss mechanisms in each unit cell of the RPBG, and we also outline optimization strategies in terms of spectral light characteristics as well as quasi-antireflection coating of the RPBGs. © 2005 Optical Society of America.
• Yang, Z. S., Kwong, N. H., Takayama, R., & Binder, R. (2005). Ultrafast coherent dynamics of optically inactive excitons in semiconductors. Europhysics Letters, 69(3), 417-423.
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  Abstract: The center-of-mass momentum distribution of optically created excitons in semiconductors is known to be constrained by the (very small) light momenta at times immediately following the excitation, and it is governed by incoherent scattering processes on longer time scales. The present theoretical analysis suggests that, on intermediate time scales, nonlinear mean-field interactions between excitons lead to a coherent, wave-like evolution in the momentum distribution of optically inactive excitons. Proposals for possible experimental verification of these predictions are discussed.
• Kwong, N. H., Binder, R., & Lindberg, M. (2004). Quantum-dot quantum-interference infrared photodetector: Design proposal and modeling of performance characteristics. Optics Letters, 29(21), 2536-2538.
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  PMID: 15584286;Abstract: A novel design of an IR photodetector operating at wavelengths around 10 μm is presented. It is based on a three-level quantum coherence effect in semiconductor quantum dots as measured in balanced-homodyne detection in a Mach-Zehnder interferometer. The advantage of this design is the combination of room-temperature operation and fast response time, whereas the major drawback is the high noise-equivalent power. © 2004 Optical Society of America.
• Kwong, N. H., Rumyantsev, I., Binder, R., & Smirl, A. L. (2004). The connection between phenomenological few-level models and microscopic theories in the nonlinear optics of semiconductors. OSA Trends in Optics and Photonics Series, 97, 559-560.
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  Abstract: We demonstrate a formal similarity between the evolution equation of the third-order inter-band polarization in a phenomenological model and that in microscopic theories for semiconductor optics, thereby providing a microscopic interpretation of the phenomenological model. © 2004 Optical Society of America.
• Lindberg, M., & Binder, R. (2004). Theoretical foundation of transversal light forces in semiconductors. OSA Trends in Optics and Photonics Series, 97, 227-228.
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  Abstract: It is shown that, similar to the case of atomic and molecular systems, there exist transversal light forces on electrons and holes in semiconductors. However, semiconductor-specific aspects yield important differences to atomic light forces. © 2004 Optical Society of America.
• Rumyantsev, I., Kwong, N. H., Binder, R., Gansen, E. J., & Smirl, A. L. (2004). χ⁽³⁾ analysis of all-optical polarization switching in semiconductor quantum wells. Physical Review B - Condensed Matter and Materials Physics, 69(23), 235329-1-235329-9.
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  Abstract: A theoretical and experimental analysis of an all-optical polarization switching technique that has been demonstrated recently is presented. The analysis is restricted to the lowest-order nonlinear regime (χ(3) regime). The theory allows for a detailed analysis of the switching action, which is based on near-resonant optical excitation of spin-polarized excitons. The theoretical results are found to be in good agreement with experimental data. The respective contributions of phase-space blocking and various many-particle interaction and correlation terms to the switching process are identified and studied as function of experimentally adjustable parameters. The resulting parametric dependence of the switching action is used as a basis for proposals for further optimization of the device.
• Takayama, R., Kwong, N., Rumyantsev, I., Kuwata-Gonokami, M., & Binder, R. (2004). Material and light-pulse parameter dependence of the nonlinear optical susceptibilities in the coherent χ⁽³⁾ regime in semiconductor quantum wells. Journal of the Optical Society of America B: Optical Physics, 21(12), 2164-2174.
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  Abstract: A detailed numerical study of the third-order nonlinear optical susceptibilities (χ(3)) of semiconductor quantum wells is presented. The dependence of χ(3) on material parameters (electron-hole mass ratio and exciton linewidths), on the light polarization configuration (co- and countercircularly polarized) and on the spectral configuration is discussed. The goal of this study is to map out the nonlinear phase shift per quantum well and a related figure of merit caused by quasi-resonant excitonic and biexcitonic nonlinearities induced by picosecond light pulses. The study is based on the dynamics-controlled truncation formalism and evaluated under the assumption that only 1s-heavy-hole excitons contribute to the nonlinearities. It includes all correlation effects (exciton-exciton scattering in the singlet and triplet channels and coherent biexciton formation in the singlet channel) that contribute within the coherent excitonic χ(3) regime. © 2004 Optical Society of America.
• Yang, Z. S., Kwong, N. H., & Binder, R. (2004). su(N,N) algebra and constants of motion for bosonic mean-field exciton equations. Physical Review B - Condensed Matter and Materials Physics, 70(19), 1-11.
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  Abstract: The ultrafast (picosecond) coherent dynamics of exciton systems in semiconductors can be approximately described by bosonic mean-field equations. These equations are nonlinear and therefore difficult to solve analytically. It is thus important to study the general dynamical properties of these equations, such as the underlying symmetry and corresponding conservation laws. It is shown in this paper that, for an N-species exciton system (e.g., heavy-hole and light-hole excitons), a mean-field Hamiltonian (including the coupling to external fields and fermionic corrections) can be formulated which is a member of the su(N,N) algebra. As a consequence, the equations of motion for the center-of-mass momentum dependent exciton distribution and the coherent biexciton amplitude can be cast into a form similar to that of the optical Bloch vector in two-level atoms that belong to the algebra su(2) [or, more generally, N-level atoms with algebra su(N)]. It is shown that the analog to the Bloch sphere in N-level atoms is an unbounded hypersurface (generalized hyperboloid) that constrains the motion of the exciton distribution and coherent biexciton amplitude. Further constants of motions that constrain the motion on the hypersurface are found from an su(N,N) generalization to the Hioe-Eberly method in su(N) systems (N-level atoms).
• Hawkins, S. A., Gansen, E. J., Stevens, M. J., Smirl, A. L., Rumyantsev, I., Takayama, R., Kwong, N. H., Binder, R., & Steel, D. G. (2003). Differential measurements of Raman coherence and two-exciton correlations in quantum wells. Physical Review B - Condensed Matter and Materials Physics, 68(3), 353131-3531311.
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  Abstract: Quantum beats involving the light-hole and heavy-hole excitons in GaAs quantum wells are studied using both conventional and novel temporally gated differential detection techniques. The contributions of the exciton-exciton correlations are separated from those of the intervalence-band Raman coherence and the interband (population) coherence by monitoring the signal in the probe direction and by taking advantage of the polarization selection rules for the excitonic transitions. The results are shown to be in agreement with a theoretical analysis based on the dynamics-controlled truncation formalism.
• Lindberg, M., & Binder, R. (2003). Transversal light forces in semiconductors. Journal of Physics Condensed Matter, 15(7), 1119-1135.
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  Abstract: The transversal light force is a well established effect in atomic and molecular systems that are exposed to spatially inhomogeneous light fields. In this paper it is shown theoretically that in an excited semiconductor, containing an electron-hole plasma or excitons, a similar light force exists, if the semiconductor is exposed to an ultrashort spatially inhomogeneous light field. The analysis is based on the equations of motion for the Wigner distribution functions of charge carrier populations and interband polarizations. The results show that, while the light force on the electron-hole plasma or the excitons does exist, its effects on the kinetic behaviour of the electron-hole plasma or the excitons are different compared to the situation in an atomic or molecular system. A detailed analysis presented here traces this difference back to the principal differences between atoms and molecules on the one hand and electron-hole plasmas or excitons on the other hand.
• Phillips, M. C., Wang, H., Rumyantsev, I., Kwong, N. H., Takayama, R., & Binder, R. (2003). Electromagnetically Induced Transparency in Semiconductors via Biexciton Coherence. Physical Review Letters, 91(18), 1836021-1836024.
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  PMID: 14611283;Abstract: The electromagnetically induced transparency (EIT) in a GaAs quantum well was studied. A biexciton coherence was used to induce the strong EIT. A control pulse was coupled to a biexciton resonance to set up the destructive quantum interference in the EIT. It was observed that the many particle interactions can be used to manipulate the quantum coherences.
• Phillips, M., Wang, H., Rumyantsev, I., Kwong, N. H., Takayama, R., & Binder, R. (2003). Electromagnetically-induced transparency at the exciton resonance. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 89, QFD1/1-QFD1/2.
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  Abstract: We report the experimental demonstration of electromagnetically-induced transparency (EIT) in a GaAs quantum well, in which the absorption of an exciton resonance is reduced by more than twenty-fold. The destructive quantum interference for EIT is set up by a biexciton coherence. ©2000 Optical Society of America.
• Rumyantsev, I., Kwong, N. H., Gansen, E. J., Smirl, A. L., & Binder, R. (2003). Many-particle theory of all-optical polarization switching in semiconductor quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 89, QThJ13/1-QThJ13/2.
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  Abstract: A microscopic many-body theory is used to analyze an all-optical polarization switching technique that has been demonstrated recently. The respective contributions of phase-space blocking and various exciton interaction and correlation terms to the switching process are calculated. ©2002 Optical Society of America.
• Rumyantsev, I., Kwong, N. H., Takayama, R., Binder, R., Phillips, M., & Wang, H. (2003). Optically induced biexciton energy shift in semiconductor quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 89, QThPDA7/1-QThPDA7/2.
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  Abstract: The energy level shift of a coherent biexciton (bound two-exciton state) in a semi-conductor has been observed experimentally and analyzed theoretically. The shift, which results from the presence of excitons, can be related to the AC Stark shifts of the underlying exciton states. ©2003 Optical Society of America.
• Tao, L. i., Wang, H., Kwong, N. H., & Binder, R. (2003). Electromagnetically induced transparency via electron spin coherence in a quantum well waveguide. Optics Express, 11(24), 3298-3303.
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  PMID: 19471458;Abstract: We propose and analyze a novel scheme to realize electromagnetically induced transparency (EIT) via robust electron spin coherence in semiconductor quantum wells. This scheme uses light hole transitions in a quantum well waveguide to induce electron spin coherence in the absence of an external magnetic field. For certain polarization configurations, the light hole transitions form a crossed double-V system. EIT in this system is strongly modified by a coherent wave mixing process induced by the electron spin coherence. ©2003 Optical Society of America.
• Yang, Z. S., Kwong, N. H., Takayama, R., & Binder, R. (2003). Coherent dynamics of optically-inactive excitons in semiconductor quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 89, QThM4/1-QThM4/2.
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  Abstract: Ultrafast coherent dynamics of optically-inactive excitons in photo-excited quantum wells are investigated. The exciton momentum distribution follows an interesting moving pattern driven by the Coulomb coupling between the interband polarization and excitons with non-zero momenta. ©2002 Optical Society of America.
• Rumyantsev, I., Binder, R., Takayama, R., & Kwong, N. H. (2002). On the interplay between excitonic and biexcitonic quantum coherences. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 74, 269-270.
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  Abstract: An overview is given on a theoretical study demonstrating that nonlinear effects similar to those underlying in EIT in 3-level atoms can be realized in the 3rd-order nonlinear regime with excitonic and biexcitonic coherences in semiconductors. The implications of this work are outlined.
• Rumyantsev, I., Binder, R., Takayama, R., Kwong, N. H., Stevens, M. J., & Smirl, A. L. (2002). Signatures of exciton correlations in the time-resolved vectorial polarization state of four-wave mixing signals from semiconductor quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 74, 196-197.
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  Abstract: The microscopy many-body theory applied to the time-resolved vectorial polarization state of the four-wave mixing (FWM) signal documents two-exciton correlations. Under the experimental conditions, the biexciton dephasing rate is much less than twice the exciton dephasing rate.
• Rumyantsev, I., Kwong, N. H., Takayama, R., & Binder, R. (2002). Effects of intervalence band coherences on the coherently coupled heavy-hole-light-hole stark shift in semiconductor quantum wells. Physical Review B - Condensed Matter and Materials Physics, 65(24), 2453251-24532510.
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  Abstract: A theoretical study of the coherently coupled heavy-hole-light-hole optical Stark effect in semiconductor quantum wells is presented. Based on a detailed investigation of the various many-body contributions to the Stark shifts, we identify a parameter regime in which the existence of intervalence band coherences (analogous to the nonradiative Raman coherence in three-level atoms) can be inferred from the coherently coupled heavy-hole-light-hole excitonic optical Stark shift. The analysis is performed for the third-order nonlinear optical regime (X3 regime), and is based on the dynamics-controlled truncation (DCT) formalism. It includes the relevant optical selection rules, excitonic and two-exciton-correlation (e.g., biexcitonic) effects.
• Takayama, R., Kwong, N. H., Aoki, T., Kuwata-Gonokami, M., & Binder, R. (2002). Influence of exciton line shape asymmetries on four wave mixing spectra of semiconductor microcavities. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 74, 217-218.
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  Abstract: Using a full microscopic many-body theory, an attempt was made to compute four-wave mixing spectra of a thin semiconductor quantum well microcavities within the lowest-order nonlinear regime. Focus was on heavy-hole 1s excitons and corresponding two-exciton correlations. Evidence was obtained that there is a non-trivial interplay between linear excitonic lineshapes and nonlinear four-wave mixing spectra.
• Takayama, R., Kwong, N. H., Rumyantsev, I., Kuwata-Gonokami, M., & Binder, R. (2002). T-matrix analysis of biexcitonic correlations in the nonlinear optical response of semiconductor quantum wells. European Physical Journal B, 25(4), 445-462.
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  Abstract: A detailed numerical analysis of excitom-exciton interactions in semiconductor quantum wells is presented. The theory is based on the dynamics-controlled truncation formalism and evaluated for the case of resonant excitation of 1s-heavy-hole excitons. It is formulated in terms of standard concepts of scattering theory, such as the forward-scattering amplitude (or T-matrix). The numerical diagonalization of the exciton-exciton interaction matrix in the 1s-approximation yields the excitonic T-matrix. We discuss the role of the direct and exchange interaction in the effective two-exciton Hamiltonian, which determines the T-matrix, evaluated within the 1s-subspace, and also analyze the effects of the excitonic wave function overlap matrix. Inclusion of the latter is shown to effectively prevent the 1s-approximation from making the Hamiltonian non-hermitian, but a critical discussion shows that other artefacts may be avoided by not including the overlap matrix. We also present a detailed analysis of the correspondence between the excitonic T-matrix in the 1s-approximation and the well-known T-matrix governing two-particle interactions in two dimensional systems via short-range potentials.
• Yang, Z. S., Binder, R., Kwong, N. H., & Takayama, R. (2002). Adiabatic following of incoherent exciton density in semiconductor quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 74, 220-221.
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  Abstract: One incoherent quantity is the incoherent exciton density which is created by excitons scattering each other out of the coherent component. Other than its role in the dephasing and relaxation of the system, the incoherent exciton density has not received much attention. This paper discusses results of theoretical study on the behavior of this quantity and related correlation functions under conditions that inhibit relaxation.
• Kwong, N. H., Takayama, R., & Binder, R. (2001). Theoretical study of the polarization dependence of third-order optical nonlinearities in semiconductor microcavities. Proceedings of SPIE - The International Society for Optical Engineering, 4283, 150-158.
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  Abstract: We present a microscopic theory of the coherent third order (χ(3)) optical response of semiconductor quantum well microcavities, specialized to the four-wave-mixing configuration in the spectral vicinity of the lowest exciton frequency. The theory is that of a quantum mechanical many-electron system dipole-coupled to a classical radiation field. The many-electron dynamics is treated within the dynamics-controlled-truncation formalism restricted to the 1s-exciton subspace. Within this limitation, all Coulomb correlation effects are included, resulting in an effective theory of (virtual) exciton-polariton scattering. The theory is evaluated for various polarization configurations each of which depends differently on the underlying many-body effects, such as phase-space filling, Hartree-Fock exchange, and two-exciton correlations (including two-exciton continuum scattering and coherent biexciton formation).
• Kwong, N. H., Takayama, R., Rumyantsev, I., Kuwata-Gonokami, M., & Binder, R. (2001). Evidence of nonperturbative continuum correlations in two-dimensional exciton systems in semiconductor microcavities. Physical Review Letters, 87(2), 027402/1-027402/4.
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  Abstract: Microcavity four-wave mixing (FWM) signals are sensitive probes of the exact nature of exciton-exciton correlations in quasi-two dimensions. A theory-experiment comparison is presented to demonstrate the failure of the 2nd Born approximation.
• Kwong, N. H., Takayama, R., Rumyantsev, I., Kuwata-Gonokami, M., & Binder, R. (2001). Third-order exciton-correlation and nonlinear cavity-polariton effects in semiconductor microcavities. Physical Review B - Condensed Matter and Materials Physics, 64(4), 453161-4531615.
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  Abstract: We present a microscopic theory of the coherent third-order (X(3)) optical response of semiconductor quantum well microcavities, specialized to the four-wave-mixing configuration in the spectral vicinity of the lowest exciton frequency. The theory is that of a quantum-mechanical many-electron system dipole coupled to a classical radiation field. The many-electron dynamics is treated within the dynamics-controlled-truncation formalism restricted to the 1 s-exciton subspace. Within this limitation, all Coulomb correlation effects are included, resulting in an effective theory of (virtual) exciton-polariton scattering. Good quantitative agreement of the theory is obtained in comparison to the experiments reported by Gonokami et al., Phys. Rev. Lett. 79, 1341 (1997). This comparison reveals the signatures of both the bound biexciton and the exciton-exciton scattering (continuum) correlations. Furthermore, a proper calculation of the scattering correlations is shown to be important: each of two common approximations, the Markov and the second Born, results in clear discrepancies from the data.
• Binder, R., & Lindberg, M. (2000). Three-band excitonic Rabi oscillations in semiconductor quantum wells. Physical Review B - Condensed Matter and Materials Physics, 61(4), 2830-2836.
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  Abstract: Optical Rabi oscillations in atomic two-level systems and excitonic Rabi oscillations in two-band semiconductors are already well established. In contrast to two-level (or two-band) Rabi oscillations, three-level (or three-band) Rabi oscillations offer a rich variety of oscillation dynamics involving both radiative and nonradiative (Raman) transitions. We analyze excitonic three-band Rabi oscillations in semiconductor quantum wells and study, in particular, the role of band-coupling effects and Coulomb effects. ©2000 The American Physical Society.
• Binder, R., Rumyantsev, I., Kwong, N. H., & Takayama, R. (2000). On the identification of intervalence-band coherences in semiconductor quantum wells. Physica Status Solidi (B) Basic Research, 221(1), 169-178.
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  Abstract: A theoretical analysis of intervalence-band coherences is presented. These optically created non-radiative coherences are generalizations of non-radiative coherences in atomic and molecular three-level systems. Whereas in three-level systems these coherences are the basis of important and well-established nonlinear effects, the interpretation of experimental evidence for such coherences in semiconductors needs to be supported by many-body theory. Based on the dynamics-controlled truncation formalism, the respective contributions of intervalence-band coherences and coherent biexcitonic correlations in time-integrated differential transmission spectroscopy is investigated. It is found that the contribution of the biexcitonic correlations to the observable heavy-hole-light-hole beats can be eliminated, either by reducing the light pulse duration or by choosing the central frequency of the light pulses at the heavy-hole exciton.
• Burak, D., & Binder, R. (2000). Microscopical model for polarization stability in optically anisotropic VCSELs. Proceedings of SPIE - The International Society for Optical Engineering, 3944, I/-.
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  Abstract: A comparative study between microscopic and macroscopic models describing polarization switching in optically anisotropic VCSELs is presented. The microscopic model includes: (i) steady-state, many-body multi-band microscopic theory for the optical response of semiconductor quantum wells; (ii) the polarization properties of vectorial eigenmodes of VCSEL structures including mode-dependent losses and frequencies; (iii) realistic model for optical anisotropies resulting from intentional or unintentional strata in an active quantum-well layer. A macroscopic model is derived from this microscopic model. It provides a rigorous generalization of the phenomenological approaches to the description of polarization properties of VCSELs used commonly in the literature. The optical anisotropy of the VCSEL structure is assumed to result from anisotropic strain of the active quantum well material. The valence band anisotropy and heavy-hole light-hole mixing effects determine the system characteristics like anisotropic gain and refractive index. The results of microscopic and macroscopic models agree very well for input/output characteristics of anisotropic VCSELs. Also, the stability properties of polarization eigenmodes are qualitatively the same, although the ranges of stability are quantitatively different for both approaches. Incorporation of many-body effects into the analysis usually diminishes the agreement between microscopic and macroscopic theories.
• Kwong, N. H., & Binder, R. (2000). Green's function approach to the dynamics-controlled truncation formalism: Derivation of the χ⁽³⁾ equations of motion. Physical Review B - Condensed Matter and Materials Physics, 61(12), 8341-8358.
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  Abstract: The dynamics-controlled truncation (DCT) formalism is a successful microscopic approach that describes coherent correlations in optically excited semiconductors. For practical reasons (including numerical evaluations), its application is limited to lowest-order nonlinearities, such as the χ(3) regime. Therefore, it is not convenient to use this formalism to examine the role played by incoherent many-body effects, such as carrier-carrier scattering and screening. Traditionally, the most powerful approach to study incoherent effects and correlations in highly excited semiconductors is that of nonequilibrium Green's functions (NGF). A combination of the insights and technical advantages provided by the two (NGF and DCT) approaches will lead to a comprehensive microscopic theory for nonlinear optical phenomena in semiconductors. In this paper, we take a first step in this direction by presenting detailed one-to-one relations between the two formalisms within the χ(3) approximation. Starting from the standard perturbation theory of nonequilibrium Green's functions, we derive the essential minimal order factorization theorems, to arbitrary order, of DCT and the equations of motions for the interband polarization and the "biexcitonic" correlation function. This lays the foundation for future diagrammatic high-intensity generalizations of the DCT formalism. ©2000 The American Physical Society.
• Kwong, N. H., & Binder, R. (2000). Green's function approach to the dynamics-controlled truncation formalism: derivation of the χ⁽³⁾ equations of motion. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 51-52.
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  Abstract: A study was carried out to examine in detail the standard Feynman-Dyson perturbation theory diagrams for the Green's functions corresponding to the interband polarization, the one-particle density matrix, and the coherent biexcitonic correlation function. The surviving diagrams were classified in increasing order of the external field. In each order up to order three, it was shown that all non-vanishing terms contributing to the relevant Green's functions can be ressumed to yield closed equations of motion.
• Kwong, N. H., Takayama, R., Rumyantsev, I., & Binder, R. (2000). Exciton-scattering and biexciton contributions to four-wave mixing signals in semiconductor quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 78-79.
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  Abstract: Thorough understanding of the many-particle effects in four-wave-mixing (FWM) can only be achieved from a strict justification as well as extension of the phenomenological many-body concepts on the basis of a fully microscopic theory. This article discusses the results of such a study. The results include theoretical identification, careful numerical analysis of all matrix elements entering the excitonic X-theory and a comparison with experimental data from the literature.
• Rumyantsev, I., Kwong, N. H., Takayama, R., & Binder, R. (2000). Comparison of phenomenological models with a microscopic theory for semiconductor optical nonlinearities. Proceedings of the 8th International Symposium Nanostructures: Physics and Technology, 287-290.
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  Abstract: A microscopic theory of the third order coherent semiconductor optical response is used for the investigation of four-wave mixing signals. The theory is based on the dynamics-controlled truncation formalism and evaluated for the case of resonant excitation of heavy-hole excitons. This approach allows for a direct comparison with other theories (microscopic or phenomenological), and yields a detailed understanding of important many-body effects such as excitation-induced dephasing.
• Binder, R. (1999). Rabi oscillations and Raman coherences in semiconductor quantum wells. IQEC, International Quantum Electronics Conference Proceedings, 13-.
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  Abstract: The relationship between generalized Rabi oscillations involving optical transitions in three band systems and Raman coherences is investigated. The system under observation is a conventional GaAs semiconductor quantum well in which only the lowest subband of the conduction, the heavy-hole (hh) and light-hole (lh) bands need to be taken into account. Two simultaneous, strong sub-picosecond pulses of opposite circular polarization, spectrally centered at the hh and the lh-excitons, respectively, are considered. In this configuration, both the intervalence-band Raman coherence and excitonic Rabi oscillations are created.
• Binder, R., & Lindberg, M. (1998). Ultrafast adiabatic population transfer in p-doped semiconductor quantum wells. Physical Review Letters, 81(7), 1477-1480.
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  Abstract: The light-induced adiabatic population transfer of holes from the heavy-hole (hh) to the light-hole (lh) band in p-doped semiconductor quantum wells is investigated theoretically. The exact analog to the population-trapped state (PTS) used in atomic and molecular adiabatic population transfer does not exist in a semiconductor due to the continuum of transition energies and the dynamic light-induced shifts thereof. However, it is found that the population transfer only requires an approximate PTS condition to be fulfilled. As for a possible observation of the effect, the transient creation of a hh exciton resonance at the expense of the lh exciton is predicted.
• Binder, R., & Lindberg, M. (1998). Ultrafast adiabatic population transfer in p-doped semiconductor quantum wells. Technical Digest - European Quantum Electronics Conference, 108-.
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  Abstract: The ultrafast adiabatic heavy hole-light hole (HH-HL) population transfer in p-doped semiconductor quantum wells, wherein the transfer of holes from the HH band to the LH band is possible without creating electrons in the process, is theoretically analyzed. The theory involves a numerical solution of the equation of motion for the interband polarizations and intraband populations within an appropriate six-band model. It takes into account the Coulomb interaction and the linear and nonlinear exciton effects.
• Burak, D. W., & Binder, R. H. (1998). Theoretical analysis of polarization properties of VCSEL eigenmodes. Proceedings of SPIE - The International Society for Optical Engineering, 3283, 269-279.
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  Abstract: A theoretical analysis of the polarization properties of Vertical-Cavity Surface-Emitting Lasers is presented. A model is derived which contains the influence of material (strain in cavity layers, scattering rates, refractive indices of layers) and cavity design (size, number of layers) parameters on input/output characteristics of the system. The electromagnetic field is represented as a superposition of cold-cavity vectorial eigenmodes of the VCSEL cavity. Each eigenmode is characterized by its resonant wavelength, threshold gain and 3D vectorial eigenmode profile. The electromagnetic field is then coupled to semiconductor Bloch equations describing the active quantum well material. The theory is evaluated for the case of two orthogonal HE 11-like modes and a six-band model of quantum well. ©2003 Copyright SPIE - The International Society for Optical Engineering.
• Burak, D., & Binder, R. (1998). Electromagnetic characterization of vertical-cavity surface-emitting lasers based on a vectorial eigenmode calculation. Applied Physics Letters, 72(8), 891-893.
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  Abstract: A complete theoretical approach to the electromagnetic properties of vertical-cavity surface-emitting lasers (VCSELs) is presented. The solution of the 3D vector Maxwell equations is obtained by means of a generalized vectorial transform matrix. Results for the characterization of laser modes include modal frequencies, cavity losses, and eigenmode light-field vector patterns. As an example, modal properties of air-post index-guided VCSELs are analyzed for various cavity design parameters. Scattering losses due to modal mismatch at cavity interfaces are found to be small and, hence, would not overcompensate potential cavity design improvements based on increased relative index steps. © 1998 American Institute of Physics.
• Burak, D., & Binder, R. (1998). Full vectorial eigenmode analysis of VCSELs: Threshold gain values and modal frequencies. Proceedings of SPIE - The International Society for Optical Engineering, 3286, 220-229.
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  Abstract: A complete theoretical approach to the electromagnetic properties of vertical-cavity surface-emitting lasers is presented. The Maxwell's equations are solved by using the local mode expansion technique. The transverse components of the electromagnetic field in each layer of the cavity are expressed in terms of complete set of orthogonal local modes. Matching these components at each boundary yields the vectorial transform matrix of the structure. The cavity eigenmodes are found from the condition of vanishing in-coming amplitudes. Results for the characterization of laser modes include modal frequencies, threshold gains and eigenmode light-field vector patterns. The influence of scattering losses on threshold gain values as a function of VCSEL radius, mode order and number of dielectric layers are discussed.
• Kwong, N. H., Bonitz, M., Binder, R., & Köhler, H. (1998). Semiconductor Kadanoff-Baym equation results for optically excited electron-hole plasmas in quantum wells. Physica Status Solidi (B) Basic Research, 206(1), 197-203.
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  Abstract: We present results from solutions of the semiconductor Kadanoff-Baym equations (full two-time semiconductor Bloch equations) with self-energies in quasistatic Born approximation, for GaAs single quantum wells. We concentrate on memory and correlation effects under fs-pulse excitation conditions. A remarkable feature is the observed kinetic energy increase which is due to the build-up of correlations among the generated carriers. We demonstrate that the two-time approach is (i) very well suited to study correlation phenomena both on short and long times, thereby avoiding well-known problems of one-time kinetic equations, and (ii) that it is becoming practical with the use of efficient integration techniques.
• Micallef, R. W., Kivshar, Y. S., Love, J., Burak, D., & Binder, R. (1998). Spatial solitons generated from nonlinear guided modes. Technical Digest - European Quantum Electronics Conference, 183-184.
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  Abstract: Optical waveguides provide an efficient way of confining and propagating light with the additional advantage of allowing the observation of nonlinear effects at relatively low input powers. However, to create a steerable reconfigurable waveguide in a bulk medium, a different concept based on the propagation of self-guided beams or spatial solitons may be used. These two concepts were combined and applied to the problem of the generation of spatial solitons by using nonlinear guided modes of a nonlinear slab waveguide. The different types of single and multiple spatial solitons generated by this method are described, and the soliton parameters generated by the method are determined from numerical simulations.
• Micallef, R. W., Kivshar, Y., Love, J. D., Burak, D., & Binder, R. (1998). Generation of spatial solitons using non-linear guided modes. Optical and Quantum Electronics, 30(7-10), 751-770.
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  Abstract: We investigate how two-dimensional spatial optical solitons can be generated in a non-linear Kerr medium using the non-linear guided modes of a weakly-guiding slab waveguide with a linear core and a non-linear cladding as the source of excitation. Symmetric, antisymmetric and asymmetric non-linear modes are considered, from which we determine the parameters of single solitons, oscillating two-soliton bound states, and two repelling solitons, respectively. Both the beam propagation method and inverse scattering transform are used.
• Milster, T., Jiang, W., Walker, E., Burak, D., Claisse, P., Kelly, P., & Binder, R. (1998). A single-mode high-power vertical cavity surface emitting laser. Applied Physics Letters, 72(26), 3425-3427.
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  Abstract: We show how a structural element introduced into a vertical cavity surface emitting laser (VCSEL) results in the device operating in single stable high-order mode. The results from a 55 μm diameter device, λ=772nm, are presented. The stability of the mode structure is investigated as a function of injection current. A simple theory, based on a modal loss discrimination mechanism in VCSELs with slightly perturbed mirrors, is used to explain the preferred lasing mode in VCSEL structures using a central etched well. © 1998 American Institute of Physics.
• Binder, R. (1997). Interaction-induced polarization rotation in anisotropic semiconductor quantum wells. Physical Review Letters, 78(23), 4466-4469.
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  Abstract: It is shown that the ultrafast coherent nonlinear optical effect of interaction-induced polarization rotation can be used to identify and study interaction processes in many-body systems. In the theoretical example presented here, signatures of coherent exciton-exciton interactions are identified in polarization trajectories in Poincaré's Cartesian complex plane of polarization, which is used to visualize the differential polarization rotation (or. alternatively, the polarization of the reflected light) of femtosecond light pulses in uniaxially strained quantum wells. Interaction processes are found to affect significantly the polarization trajectories, including their symmetry properties.
• Binder, R. (1997). Nonlinear excitonic birefringence in anisotropic semiconductor quantum wells. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 12, 38-39.
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  Abstract: A new method, the time-resolved nonlinear differential polarimetry, was developed to analyze the ultrafast exciton-exciton interactions in uniaxially strained quantum wells. Semiconductor GaAs quantum wells which exhibited dichroism and birefringence in the spectral vicinity of the heavy hole (hh) exciton resonance were used in the study. The strong light pulse was numerically simulated to compute for the induced nonlinear optical polarization. Results that contain only Pauli blocking effects were seen to differ from those containing exciton interaction effects resulting from the Coulomb interaction.
• Binder, R. H. (1997). Theory of ultrafast optical nonlinearities of uniaxially strained quantum wells. Proceedings of SPIE - The International Society for Optical Engineering, 2994, 452-459.
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  Abstract: A theoretical study of ultrafast many-body effects in anisotropic semiconductors is presented. Signatures of coherent exciton-exciton interactions are identified in polarization traces in Poincare's cartesian complex plane of polarization which is used to visualize the differential polarization rotation of ultrashort light pulses due to excitons in uniaxially strained quantum wells.
• Binder, R. H., Koehler, H. S., Kwong, N., & Bonitz, M. (1997). Theory of momentum orientation relaxation in semiconductors. Proceedings of SPIE - The International Society for Optical Engineering, 2994, 690-695.
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  Abstract: We present numerical results for charge-carrier relaxation processes by carrier-carrier scattering in various semiconductor structures. Common to all examples is the aspect of anisotropy. Our results are based on a generalized quantum Boltzmann equation. Specifically, we solve the Kadanoff-Bayn equations for the relevant two-time Green's function. The systems under consideration are bulk GaAs with anisotropically photo-excited electrons and hexagonal CdS.
• Binder, R., Köhler, H., Bonitz, M., & Kwong, N. (1997). Green's function description of momentum-orientation relaxation of photoexcited electron plasmas in semiconductors. Physical Review B - Condensed Matter and Materials Physics, 55(8), 5110-5116.
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  Abstract: We present numerical results for the momentum-orientation relaxation of optically excited electron plasmas in bulk semiconductors. Our results are based on the full two-time Green's function approach for carrier-carrier scattering and are compared to the results obtained within the conventional quantum Boltzmann equation. Defining "memory effects" by this comparison, we find memory effects mainly to be differences in the time-scale of the relaxation process rather than distinct qualitative features. Within the limitations of our isotropic static screening model, we find that, in both approaches, an initial anisotropic and nonmonotonic distribution function relaxes in a three-stage process in which the distribution becomes monotonic before it loses its anisotropy.
• Bonitz, M., Binder, R., & Köhler, H. (1997). Quantum kinetic equations: Correlation dynamics and selfenergy. Contributions to Plasma Physics, 37(2-3), 101-113.
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  Abstract: The derivation of non-Markovian quantum kinetic equations is reconsidered in the framework of density operators. Conventional derivations use for the decoupling of the BBGKY-hierarchy the assumption of vanishing three-particle correlations g123 = 0. This yields non-Markovian kinetic equations with infinite memory depth. We discuss a different closure relation to the hierarchy, which overcomes this difficulty without assumptions on weakening of initial correlations and in fact corresponds to the inclusion of selfenergy effects (beyond Hartree-Fock).
• Burak, D., & Binder, R. (1997). Cold-cavity vectorial eigenmodes of VCSEL's. IEEE Journal of Quantum Electronics, 33(7), 1205-1215.
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  Abstract: An analytical approximate solution of Maxwell's equations for the cold-cavity eigenmodes of cylindrical etched air-post vertical-cavity surface-emitting lasers (VCSEL's) is presented. In radial and azimuthal directions, the modes correspond to the hybrid modes of cylindrical optical waveguides. A vectorial transform matrix approach is derived which takes into account coupling of bound eigenmodes in VCSEL structures. The method is illustrated for the case of noncoupled modes and the corresponding simplified transform matrix approach is used to calculate the field profiles in longitudinal direction and predict the resonance wavelengths for the VCSEL eigenmodes. Although approximate, the resulting eigenmodes may be viewed as a useful alternative to full numerical solutions, especially with regard to future more comprehensive modeling of VCSEL's.
• Burak, D., & Binder, R. (1997). Dispersion-induced bifurcations of spatial soliton parameters in nonlinear planar waveguides. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 12, 71-.
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  Abstract: The dynamical collapse and break up of bright soliton Y junctions and breather solitons as a result of dispersion-induced structural bifurcations are numerically demonstrated. The propagation of light pulses in planar single-mode waveguide under the influence of normal group velocity dispersion is described by the (1+2) dimensional nonlinear Schrodinger equation. The basic steering behavior of these Y junctions is obtained from the solution of the Zakharov-Shabat eigenvalue problem for the dispersionless case.
• Burak, D., & Binder, R. (1997). Spatiotemporal bright soliton Y junctions in nonlinear planar waveguides. Journal of the Optical Society of America B: Optical Physics, 14(6), 1458-1464.
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  Abstract: The splitting and steering of ultrashort pulses propagating through a Kerr medium are investigated. This investigation extends earlier ones of cw spatial soliton Y junctions into the area of subpicosecond solitonlike pulse propagation. Besides that of the all-optical steering process, the influence of normal group-velocity dispersion and two-photon absorption is discussed. It is found that both processes modify the transmission characteristics of the system (i.e., output versus input beam intensity) in a similar way. However, two-photon absorption inhibits the steering property of Y junctions, whereas normal group-velocity dispersion enhances it. A model based on an adiabatic propagation approximation is used to explain this behavior qualitatively. © 1997 Optical Society of America.
• Burak, D., & Binder, R. H. (1997). Theoretical study of electromagnetic eigenmodes of VCSELs. Proceedings of SPIE - The International Society for Optical Engineering, 2994, 159-167.
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  Abstract: The empty-cavity electromagnetic eigenmodes of vertical- cavity surface-emitting lasers, including light-vector polarization properties, are calculated from Maxwell equations in cylindrical symmetry. The electromagnetic field in each layer is expanded into local modes of the corresponding cylindrical waveguide and the vectorial transform matrix method is used to calculate the light propagation through the structure. A simplified approach for the case of uncoupled modes is also formulated. For the cavity geometry under consideration the resonant frequencies of eigenmodes predicted within the CMA agree very well with results of exact calculations. The presented method for the empty-cavity eigenmode determination may be useful for future calculations of a steady-state laser models with semiconductor material gain parameters and carriers and temperature diffusion processes taken into account.
• Dufty, J. W., Kim, C. S., Bonitz, M., & Binder, R. (1997). Density matrix methods for semiconductor coulomb dynamics. International Journal of Quantum Chemistry, 65(5), 929-940.
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  Abstract: Current experiments on semiconductor devices using femtosecond lasers provide new theoretical challenges for the description of charge carrier dynamics. Among the new features of such experiments are states driven very far from equilibrium and probes on time scales short compared to scattering and other characteristic material relaxation times. Standard many-body methods must be modified and extended to accommodate these features. We propose that the quantum hierarchy for reduced density operators is an ideal formulation of such initial value problems and describe how the dominant effects of exchange and charge correlations can be accounted for in a simple and physically transparent closure of the hierarchy of equations. The transformations, approximations, and interpretation can be accomplished independent of any particular matrix representation. Decomposition into kinetic equations for band occupation densities and polarization densities follows in a straightforward way after the many-body problem has been brought under control. © 1997 John Wiley & Sons, Inc.
• Köhler, H., & Binder, R. (1997). The interplay of electron-phonon and electron-electron scattering within the two-time green's function description. Contributions to Plasma Physics, 37(2-3), 167-172.
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  Abstract: We present numerical results for electron-phonon and electron-electron scattering in optically excited electron plasmas in bulk semiconductors. Our results are based on the full two-time Green's function approach. They include quantum mechanical memory and correlation effects because the scattering integrals are generalizations of the conventional Boltzmann scattering integrals. The interplay of two different scattering mechanisms is studied and compared to results where only one scattering mechanism is present.
• Binder, R., Kohler, H. S., & Bonitz, M. (1996). Memory effects in the momentum orientation relaxation of optically excited plasmas in semiconductors. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 9, 154-155.
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  Abstract: In the study of memory effects in the momentum orientation relaxation, the theoretical basis of analysis are the equations of motion for the the full two-time one-particle Green's function g < (k→, t1, t2) within the screened Hartree-Fock approximation. This Green's function reduces to the distribution function of the charge carriers as function of momentum k and time t in the equal time limit: f(k→, t) = -iℏg < (qq, t, t). The numerical solution incorporates full correlation effects because it is based on an time integration in the two-dimensional t1 - t2 plane. Of course, one can apply certain additional approximations such as the Markov approximation to reduce the equation of motion to the conventional Boltzmann equation. The comparison of the results with and without such additional approximations yields important information about charge-carrier correlation contributions, memory effects, and nonkinetic energy preserving processes.
• Bonitz, M., Kremp, D., Scott, D. C., Binder, R., Kraeft, W. D., & Köhler, H. (1996). Numerical analysis of non-Markovian effects in charge-carrier scattering: One-time versus two-time kinetic equations. Journal of Physics Condensed Matter, 8(33), 6057-6071.
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  Abstract: The non-Markovian carrier-carrier scattering dynamics in a dense electron gas is investigated. Within the framework of quantum kinetic equations in the second Born approximation we study the relevance of retardation (memory) effects, energy broadening and correlation build-up for femtosecond relaxation processes. Furthermore, the important issue of total energy conservation, within various well-established approximation schemes, is analysed. The most important non-Markovian effect is shown to be the broadening of the energy delta function leading to an increase of kinetic energy with time. Our numerical analysis includes both the single-time kinetic equation and the full two-time Kadanoff-Baym equations. Our results are expected to correctly reproduce qualitative features of non-Markovian dynamics in plasmas, fluids, nuclear matter and in the intraband relaxation of semiconductors. The comparison of the exact solutions for different approximations allows suggestions for simplifications that make this kind of calculation and their extension, especially to realistic semiconductor situations, more feasible.
• Burak, D., & Binder, R. (1996). Electromagnetic eigenmodes of microdisc resonators. Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 9, 193-194.
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  Abstract: Recently a new class of semiconductor and polymer micro-resonators has been shown to achieve low-threshold lasing. The main objective of using micro-resonators is that a decrease of the size of such structure decreases the number of modes in optically active spectral region. Thus if the volume of the resonator approaches the cubic wavelength, one can obtain ultra-low-threshold lasing into a single mode. Despite their importance, modes of microdisc resonators have been analyzed only within a scalar approximation or have been treated as microsphere analog to 'whispering gallery modes' (WGM). Presented is a study of the microdisc analog to WGMs calculated from Maxwell equations.
• Burak, D., & Binder, R. H. (1996). Role of carrier diffusion in semiconductor microdisc lasers. Proceedings of SPIE - The International Society for Optical Engineering, 2693, 176-187.
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  Abstract: A theoretical analysis of the influence of carrier diffusion on the threshold characteristics of semi-conductor microdisc lasers is given. The cold-cavity modes (Whispering Gallery Modes) and their wavelengths are obtained from approximate analytical solutions of Maxwell's equations. In the steady-state, the parameters of these modes are modified in an active semiconductor medium by the presence of intensity dependent gain, refractive index and diffusion of the carriers. An increase of threshold current with decreasing carriers' lifetime is predicted. Also, the dependence of the mode pulling on the diffusion length is discussed. These effects can be explained by considering spatially varying carrier density and therefore the spatially dependent refractive index and gain.
• Binder, R., & Koch, S. W. (1995). Nonequilibrium semiconductor dynamics. Progress in Quantum Electronics, 19(4-5), 307-462.
• Lindberg, M., & Binder, R. (1995). Dark states in coherent semiconductor spectroscopy. Physical Review Letters, 75(7), 1403-1406.
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  Abstract: The possibility of creating dark states (a concept well known in atomic systems) in semiconductors is discussed. Based on the semiconductor Bloch equations, the analysis shows that, in spite of complications due to hand-structure and strong excitonic many-body effects, signatures of dark states should be observable in femtosecond nonlinear optical excitation experiments.
• Lindberg, M., & Binder, R. H. (1995). Optically induced ultrafast three-band coherences in semiconductor quantum wells. Proceedings of SPIE - The International Society for Optical Engineering, 2399, 480-486.
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  Abstract: Intervalence band coherences in semiconductor quantum wells induced by femtosecond light pulses are investigated. Especially, the possibility of creating dark states, known from atomic physics, in semiconductor quantum wells, is discussed. The analysis includes many-body effects due to the Coulomb interaction and bandstructure effects appropriate for GaAs quantum wells.
• Bonitz, M., Binder, R., Scott, D. C., Koch, S. W., & Kremp, D. (1994). Theory of plasmons in quasi-one-dimensional degenerate plasmas. Physical Review E, 49(6), 5535-5545.
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  Abstract: An analysis of collective longitudinal electrostatic plasma excitations in quasi-one-dimensional degenerate plasmas is presented using the dielectric function in the random phase approximation. Analytical continuation of the dielectric function into the lower energy half plane allows us to compute the complete spectrum of the collective excitations, including frequencies and damping or growth rates. In contrast to two- and three-dimensional plasmas, a multicomponent quasi-one-dimensional system at zero temperature is found to exhibit one undamped plasmon mode for each component. The conditions for the occurrence of unstable modes are investigated and the influence of temperature and collisions on the results is discussed. © 1994 The American Physical Society.
• Bonitz, M., Scott, D. C., Binder, R., & Koch, S. W. (1994). Nonlinear carrier-plasmon interaction in a one-dimensional quantum plasma. Physical Review B, 50(20), 15095-15098.
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  Abstract: Periodic growth and decay of linearly unstable plasmon modes are predicted by numerical solution of the one-dimensional collisionless quantum Boltzmann equation. The nonlinear mode stabilization is accompanied by the generation of higher harmonics. The results are analyzed using quantum generalized quasilinear theory. © 1994 The American Physical Society.
• Hu, Y. Z., Binder, R., Koch, S. W., Cundiff, S. T., Wang, H., & Steel, D. G. (1994). Excitation and polarization effects in semiconductor four-wave-mixing spectroscopy. Physical Review B, 49(20), 14382-14386.
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  Abstract: The dependence of optical four-wave-mixing (FWM) signals in semiconductors on carrier density and laser-field polarization is investigated. The theoretical and experimental analysis reveals the importance of the excitation-induced dephasing processes for the understanding of numerous published results on polarization selections rules in FWM signals. Even apparently contradictory earlier findings can be explained with this theoretical model. © 1994 The American Physical Society.
• Knorr, A., Streich, T., Schönhammer, K., Binder, R., & Koch, S. W. (1994). Asymptotic analytic solution for Rabi oscillations in a system of weakly excited excitons. Physical Review B, 49(19), 14024-14027.
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  Abstract: An asymptotic solution for light-induced exciton density oscillations in a semiconductor is calculated from the semiconductor Bloch equations in the low density limit (weak optical excitation). The analytic approximation is compared with a numerical solution of the full equations. It is shown that even for low area fields (2) density oscillations are caused by Coulomb exchange effects coupling the generated excitons and that the oscillation frequency and amplitude depend nonlinearly on the Rabi frequency of the incident field. © 1994 The American Physical Society.
• Koch, S. W., Binder, R., Hu, Y. Z., Jahnke, F., Knorr, A., Lindberg, M., & Schafer, W. (1994). Coherent interactions and femtosecond pulse propagation in semiconductors. Proceedings of the International Quantum Electronics Conference (IQEC'94), 144-145.
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  Abstract: The optical response of semiconductors on an ultrafast (femtosecond) time scale is significantly affected by many-particle interactions of the excited electrons and holes. In this paper we address three aspects: (1) coherent excitation dynamics in systems of different dimensionality, (2) signatures of memory effects in dephasing processes, and (3) pulse propagation effects. First, we show that the influence of the coherent exchange interaction, which modifies the external field and increases the effective Rabi frequency, is similar in bulk and quantum-well systems but is reduced in thick quantum wires. Secondly, we study incoherent effects. To determine the non-Markovian character of dephasing processes in a two-pulse scenario, we propose the use of chirped pulses. The theoretical results were obtained with a Gaussian memory function that models dephasing due to electronphonon scattering. Finally, the influence of exchange and correlation effects on the pulse propagation is discussed for both noninverted semiconductors and semiconductor amplifiers. The problem of long-distance propagation is addressed, and, in particular, recent results are presented for a gain-absorption compensation; these results indicate the possibility of long-distance propagation of light pulses in amplifiers.
• Lindberg, M., Binder, R., Hu, Y. Z., & Koch, S. W. (1994). Dipole selection rules in multiband semiconductors. Physical Review B, 49(24), 16942-16952.
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  Abstract: Rigorous dipole selection rules are derived for an interacting electron-hole system in a multiband semiconductor. The electronic system is described by the Coulomb many-body Hamiltonian and the valence-band structure is modeled using the Luttinger Hamiltonian in the axial approximation. For the example of a third-order analysis of polarization dependent two- and three-beam four-wave-mixing experiments the polarizations of the mixing signals are computed. Besides situations with well-defined four-wave-mixing polarizations configurations are identified where the polarization state of the outgoing signal depends on the dynamic and coherent properties of the semiconductor. © 1994 The American Physical Society.
• Lindberg, M., Hu, Y. Z., Binder, R., & Koch, S. W. (1994). (3) formalism in optically excited semiconductors and its applications in four-wave-mixing spectroscopy. Physical Review B, 50(24), 18060-18072.
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  Abstract: The truncation of the infinite hierarchy of equations of motion is discussed for optically excited semiconductors. We derive a complete set of equations of motion, which are valid up to third order in the excitation field amplitude. To illustrate the results the induced four-wave-mixing signals for linearly polarized laser fields are computed by numerically integrating the (3) semiconductor Bloch equations. As the dominating nonlinearity, a strong excitation-induced dephasing effect is obtained in the (3) regime. © 1994 The American Physical Society.
• Lindberg, M., Hu, Y. Z., Binder, R., & Koch, S. W. (1994). Many-body effects in a χ⁽³⁾ analysis of optically excited semiconductors. Proceedings of the International Quantum Electronics Conference (IQEC'94).
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  Abstract: Recently, the importance of the so-called excitation-induced dephasing (EID) effects for the understanding of four-wave-mixing signals has been discussed. In its simplest formulation this effect means that the effective dephasing time T2 of the excitonic resonance, which is measured in a four-wave-mixing experiment, depends on the intensity of the excitation light pulses. This phenomenon causes, for example, a coupling of the two spin-degenerate heavy-hole excitons in a strained GaAs sample. Whereas the general consequences of EID can be described within a partly phenomenological approach, a fully systematic microscopic approach is highly desirable. In general, the microscopic description of many-body effects in a system with Coulomb interaction is complicated by the fact that the interaction causes an infinite hierarchy of coupled equations of motion for the various expectation values. However, Axt and Stahl have recently shown that under certain circumstances this hierarchy can be truncated. Within a χ(n) expansion for the description the optical response to an external field one needs only to consider a finite number of expectation values of operators {N, M} = a1+a2+ ... aN+a1 ... aM, where 1, 2, . . . denote band and momentum variables. As an example, we illustrate in Fig. 1 the relevant operators in a χ(3) expansion, together with the corresponding couplings due to the external field and the Coulomb interaction. We apply this theory to a strained GaAs system and study four-wave-mixing signals induced by linearly polarized pulses. A complete numerical solution of the full set of equations, which might be called genralized semiconductor Bloch equations (see, for example, Refs. 3 and 4), is, however, still infeasible. We therefore neglect, in a first approach, the biexciton contribution and factorize contributions from the carrier-carrier scattering. In Fig. 2 we show the computed time-resolved four-wave-mixing signal induced by colinearly-polarized and cross-linearly-polarized pump and probe pulses. The ratio of the two signals is of the order 102, indicating a strong EID effect in the low-excitation limit.
• Pereira Jr., M. F., Binder, R., & Koch, S. W. (1994). Many-body theory of nonlinear optical absorption in coupled-band quantum wells. Proceedings of the International Quantum Electronics Conference (IQEC'94), 112-113.
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  Abstract: The operation of all-optical and optoelectronic semiconductor devices near the band gap relies on their highly nonlinear optical properties. Furthermore, quantum-well devices, especially those with strained layers, outperform their bulk-material counterparts in several operational characteristics and can have their properties custom designed for specific applications to a large extent. Realistic modeling of the nonlinear interaction of light with quantum wells is possible through generalized optical Bloch equations. The equations combine the influence of many-body, strain, and band-coupling effects. Figure 1(a) shows full numerical quasi-steady-state solutions of the equation for the interband polarization that gives rise to optical spectra for a 50-angstrom In0.15 Ga0.85As-GaAs quantum well at 300 K. The compressive strain within the InGaAs layers pushes the light-hole (lh) levels out of the confining potential, and they are unbound. We clearly see the exciton bleaching and the development of negative absorption (gain) for high carrier densities. Figure 1(b) displays results for an unstrained 50-angstrom GaAs-Al0.23 Ga0.77As well. In this case both the heavy-hole (hh) and lh components of the transition dipole contribute to the (TE) spectra and the valence subbands are significantly coupled. Note the larger broadening of the lh peak. This is a consequence of the added contributions from the lh band near k ≈ 0 with the non-zero k contributions of the hh, which are due to valence-band coupling. In both Figs. 1(a) and 1(b), and for low densities, the reduction of the exciton binding energy due to phase-space filling and plasma screening compensates the red-shifting effect of the exchange and Coulomb-hole self-energy corrections. For high densities, the bandgap shrinkage overcompensates for the excitonic bleaching and the absorption peaks are red shifted. The excess red shift for GaAs is a consequence of the simple quasi-static model used. The computed refractive-index changes of the first four nonlinear spectra with respect to the linear curves of Figs. 1(a) and 1(b) are shown, respectively, in Figs. 1(c) and 1(d). The computed saturation densities for the peak of TE absorption of the hh1 exciton are Ns ≈ 0.31 for the strained case are Ns = 0.57 for the unstrained case. We have used a fit to the simple law α(N) = α0/(1 + N/Ns).
• Pereira Jr., M. F., Binder, R., & Koch, S. W. (1994). Theory of nonlinear optical absorption in coupled-band quantum wells with many-body effects. Applied Physics Letters, 64(3), 279-281.
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  Abstract: The paper presents a theoretical analysis of optical nonlinearities in a strained and lattice matched quantum wells with many-body effects. The nonlinear absorption spectra and refractive index are solved numerically by the interband polarization equation. The computed spectra with the experimental results are described in this paper for comparison purposes.
• Scott, D. C., Binder, R., Bonitz, M., & Koch, S. W. (1994). Multiple undamped acoustic plasmons in three-dimensional two-component nonequilibrium plasmas. Physical Review B, 49(3), 2174-2176.
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  Abstract: Within the random-phase approximation, we demonstrate the existence of multiple undamped acoustic plasmons in a two-component three-dimensional plasma with an isotropic momentum distribution. © 1994 The American Physical Society.
• Wang, H., Ferrio, K. B., Steel, D. G., Berman, P. R., Hu, Y. Z., Binder, R., & Koch, S. W. (1994). Transient four-wave-mixing line shapes: Effects of excitation-induced dephasing. Physical Review A, 49(3), R1551-R1554.
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  Abstract: We describe the transient four-wave-mixing (FWM) response in systems where decay of the optically induced coherence depends on the excitation level of the system. Using modified optical Bloch equations, we show that excitation-induced dephasing due to phase-interrupting excited-state interactions qualitatively modifies the temporal behavior and polarization dependence of the FWM signal. © 1994 The American Physical Society.
• Bonitz, M., Binder, R., & Koch, S. W. (1993). Carrier-acoustic plasmon instability in semiconductor quantum wires. Physical Review Letters, 70(24), 3788-3791.
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  Abstract: A novel carrier-acoustic instability is predicted for quasi-one-dimensional plasmas in semiconductor quantum wires with nonequilibrium carrier distributions. The complete collective excitation spectrum of the one-dimensional quantum plasma is obtained solving the complex dispersion relation in the random-phase approximation.
• Hu, Y. Z., Binder, R., & Koch, S. W. (1993). Photon echo and valence-band mixing in semiconductor quantum wells. Physical Review B, 47(23), 15679-15687.
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  Abstract: The coherent optical response of semiconductor quantum wells is studied theoretically using the multiband semiconductor Bloch equations which include coupling of the heavy- and light-hole bands as well as many-body Coulomb effects. For the case of a two-pulse excitation scheme it is shown how the different rotational symmetries of heavy- and light-hole bands induce a strong polarization dependence of the signal in the photon echo direction. The selection rules are based on the Kane-Luttinger theory while the transition amplitudes are obtained by numerically solving the multiband semiconductor Bloch equations. In addition, the influence of valence-band mixing effects on the optical Stark effect is demonstrated. © 1993 The American Physical Society.
• Koch, S. W., Hu, Y. Z., & Binder, R. (1993). Photon echo and exchange effects in quantum-confined semiconductors. Physica B: Physics of Condensed Matter, 189(1-4), 176-188.
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  Abstract: Photon echo calculations for semiconductor quantum dots and quantum wells are presented and the role of the Fermion exchange effects is emphasized. The echoes for the quantum-dot systems arise as a consequence of the inhomogeneous broadening due to the dot size distribution. It is shown that quantum beats are superimposed to the echo signals, suggesting a sensitive way to determine the energy level separation in these systems. In semiconductor quantum wells the inhomogeneous broadening is caused by the continuum of states for the unconfined directions of electron motion. To investigate this case the semiconductor Bloch equations are generalized to include confinement induced valence band mixing. Photon echo and phase conjugate signals are computed with and without band mixing effects. The significance of the exchange contributions is analyzed for the different configurations. © 1993.
• Sayed, K. E., Binder, R., Scott, D. C., & Koch, S. W. (1993). Undamping of acoustic plasmons in nonequilibrium plasmas. Physical Review B, 47(16), 10210-10216.
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  Abstract: Intraband pair excitation and plasmon spectra of nonequilibrium plasmas are analyzed using the dynamic dielectric function in the random-phase approximation. Nonequilibrium conditions are identified for which the Landau damping of acoustic plasmons vanishes. This acoustic-plasmon undamping is discussed for two-component plasmas and for one-component plasmas with a double-peaked distribution in momentum space. © 1993 The American Physical Society.
• Wang, H., Ferrio, K., Steel, D. G., Hu, Y. Z., Binder, R., & Koch, S. W. (1993). Transient nonlinear optical response from excitation induced dephasing in GaAs. Physical Review Letters, 71(8), 1261-1264.
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  Abstract: The leading contribution to the polarization dependent four-wave-mixing signal is shown to result from density induced dephasing processes. Experimental observations are in qualitative agreement with theoretical calculations based on the semiconductor Bloch equations where dephasing due to excitonic screening has been taken into account.
• Binder, R., Scott, D., Paul, A. E., Lindberg, M., Henneberger, K., & Koch, S. W. (1992). Carrier-carrier scattering and optical dephasing in highly excited semiconductors. Physical Review B, 45(3), 1107-1115.
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  Abstract: A quantitative analysis of carrier-carrier scattering and optical dephasing in semiconductors is presented and results are given for quasiequilibrium situations and for the relaxation of a kinetic hole in a quasithermal carrier distribution. The calculations involve direct numerical integration of the Boltzmann equation for carrier-carrier scattering in the Born approximation. The screening of the Coulomb interaction is treated consistently in the fully dynamical random-phase approximation. Carrier relaxation rates are extracted from the Boltzmann-equation solution and a quantitative test of the relaxation-time approximation for situations near thermal quasiequilibrium is performed. The parametric dependence of carrier-collision rates and dephasing on plasma density, temperature, and electron and hole masses is discussed and analyzed in terms of phase-space blocking and screening. © 1992 The American Physical Society.
• Fu, W. S., Harris Jr., J. S., Binder, R., Koch, S. W., Klem, J. F., & Olbright, G. R. (1992). Nonlinear optical properties and ultrafast response of GaAs-AlAs type-II quantum wells. IEEE Journal of Quantum Electronics, 28(10), 2404-2415.
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  Abstract: Femtosecond and CW optical nonlinearities associated with the spatial separation of electrons and holes in GaAs-AlAs type-II quantum wells are reported. Without applied electric field, the nonlinearities due to blue shift and bleaching of the heavy-hole exciton resonance are observed. An applied static longitudinal dielectric field changes these nonlinearities through the redistribution of electrons. Furthermore, optical nonlinearities and even gain for ultrahigh excitation conditions in type-II structures are reported and compared to those in similar type-I structures. The theoretical framework used for modeling the type-II system in the presence and absence of electrons is described.
• Henneberger, K., Herzel, F., Koch, S. W., Binder, R., Paul, A. E., & Scott, D. (1992). Spectral hole burning and gain saturation in short-cavity semiconductor lasers. Physical Review A, 45(3), 1853-1859.
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  Abstract: A coupled set of equations for carrier distributions and stimulated emission in a semiconductor laser is presented, based on a nonequilibrium Greens-function formulation. Carrier momentum-dependent dephasing caused by carrier-carrier scattering and frequency-dependent optical gain are shown to govern the interplay between carrier relaxation and stimulated recombination. Ignoring the interband Coulomb interaction, the coupled system of equations for the carrier distribution functions and the optical gain is solved self-consistently for a single-mode short-cavity semiconductor laser under steady-state operation conditions. Numerical results show spectral and kinetic hole burning as well as nonlinear gain saturation. © 1992 The American Physical Society.
• Knorr, A., Binder, R., Lindberg, M., & Koch, S. W. (1992). Theoretical study of resonant ultrashort-pulse propagation in semiconductors. Physical Review A, 46(11), 7179-7186.
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  Abstract: Femtosecond-pulse propagation in resonantly excited semiconductors is investigated by numerically solving the semiconductor Maxwell-Bloch equations for plane waves. For excitation at the exciton resonance, it is shown that the pulse absorption exhibits a strongly nonlinear dependence on the input pulse area. Very long propagation distances for strong pulses are observed, but even when all dephasing processes have been neglected, no lossless propagation (self-induced transparency) was found. The influence of the electron-hole many-body effects, nonequilibrium carrier relaxation, and optical dephasing on the pulse-propagation dynamics is studied. The exchange interaction in the electron-hole plasma is shown to support large propagation distances. For excitation of the continuum states, the dependence of the absorption on the intensity of the input pulse is reduced due to the rapid carrier relaxation into quasiequilibrium distributions. © 1992 The American Physical Society.
• Lindberg, M., Binder, R., & Koch, S. W. (1992). Theory of the semiconductor photon echo. Physical Review A, 45(3), 1865-1875.
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  Abstract: The semiconductor Bloch equations are solved numerically for a two-pulse photon-echo configuration. The time-dependent diffracted signal is computed and the significance of many-body effects, carrier relaxation, and dephasing is investigated in detail. Assuming femtosecond-pulse excitation at various intensities and frequencies, distinctly different results are obtained if the exciton or the continuum electron-hole-pair states are excited. It is shown that pure exciton excitation produces a free-induction decay signal and no photon echo. An echo signal is obtained only if continuum states are excited either directly by choosing the central pulse frequencies appropriately or if the band-gap renormalization is sufficiently strong to shift continuum states into resonance. A continuous transition between free-induction decay and photon-echo signal is obtained with increasing excitation amplitude. A perturbative analytical analysis of the equations allows one to identify the role of the many-body effects in producing the different features. © 1992 The American Physical Society.
• Paul, A. E., Binder, R., & Koch, S. W. (1992). Spectral hole burning and light-induced band splitting in the gain region of highly excited semiconductors. Physical Review B, 45(11), 5879-5882.
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  Abstract: A many-body analysis of spectral hole burning and light-induced band renormalization in the gain region of an initially inverted semiconductor is presented. The results are based on the numerical solution of the semiconductor Bloch equations, specialized to the case of noncopropagating pump-and-probe light fields. These equations account for coherent pump-probe scattering and include the Coulomb correlation between charge carriers. They also contain optical dephasing and carrier-carrier scattering rates that are computed within the random-phase approximation. © 1992 The American Physical Society.
• Scott, D. C., Binder, R., & Koch, S. W. (1992). Ultrafast dephasing through acoustic plasmon undamping in nonequilibrium electron-hole plasmas. Physical Review Letters, 69(2), 347-350.
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  Abstract: Strong enhancement of acoustic plasmons in optically excited nonequilibrium electron-hole plasmas in bulk semiconductors is shown to cause ultrashort (∼10 fs) dephasing times and very high carrier-carrier scattering rates.
• Binder, R., Galbraith, I., & Koch, S. W. (1991). Theory of band-edge optical nonlinearities in type-I and type-II quantum-well structures. Physical Review B, 44(7), 3031-3042.
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  Abstract: A theoretical analysis of the many-body effects in the band-edge absorption spectra of highly excited type-I and type-II semiconductor quantum-well structures is presented. The situation of a homogeneous electron-hole plasma in a usual type-I structure is compared and contrasted to the situation in a type-II structure, where the electron and hole plasmas are spatially separated into adjacent layers. The plasma effects are determined through numerical solutions of a generalized Wannier equation, which accounts for dynamical exchange and screening effects as well as Pauli blocking. In the description of dynamical screening, an alternative to the so-called Shindo approximation is developed. The induced electric-field effects in the type-II systems are investigated by solving the coupled Schrödinger and Poisson equations for the charge carriers. © 1991 The American Physical Society.
• Binder, R., Koch, S. W., Lindberg, M., Schäfer, W., & Jahnke, F. (1991). Transient many-body effects in the semiconductor optical Stark effect: A numerical study. Physical Review B, 43(8), 6520-6529.
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  Abstract: A comprehensive numerical study of the optical Stark effect and associated phenomena in semiconductors is presented. The results are obtained from numerical solutions of the full semiconductor Bloch equations for bulk and quantum-well structures. Coherent oscillations, the optical Stark effect, and adiabatic following, i.e., ultrafast bleaching and recovery of the exciton, are discussed. The relative importance of the different contributions in the semiconductor Bloch equations is identified. Optical-absorption spectra are computed for different exciton dephasing models and a large variety of pump-probe excitation parameters. © 1991 The American Physical Society.
• Olbright, G. R., Fu, W. S., Owyoung, A., Klem, J. F., Binder, R., Galbraith, I., & Koch, S. W. (1991). Cw and femtosecond optical nonlinearities of type-II quantum wells. Physical Review Letters, 66(10), 1358-1361.
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  Abstract: Femtosecond time-resolved and quasi-cw measurements of optical nonlinearities of type-II GaAs/ AlAs quantum wells are reported. A pronounced blueshift of the heavy-hole exciton is observed, which develops on a 100-ps time scale after resonant interband excitation. The experimental observations are analyzed using many-body theory, explaining exciton blueshift and dynamical evolution in terms of electron-hole Coulomb enhancement, hole-phase-space filling, and hole-plasma cooling.
• Galbraith, I., Binder, R., Koch, S. W., Olbright, G. R., Owyoung, A., Klem, J., & Fu, W. S. (1990). Many-body effects in type II heterostructures. XVII International Conference on Quantum Electronics. Digest of, 126-127.
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  Abstract: A theoretical description of large optical nonlinearities in type II heterostructures was derived. The electronic states in such structures confine the electrons and holes in spatially separate layers. The interband absorption of the GaAs layer in the presence of a quasi-equilibrium hole plasma was calculated. This involves solving the Bethe-Salpeter equation containing dynamic screening of the Coulomb potential, the corresponding Hartree-Fock self-energies, and phase-space filling. The calculated absorption spectra show a large blue shift and bleaching of the heavy-hole exciton in agreement with recent experimental results. Combining the space charge shifts with the many-body bandgap renormalization, the shift in the photoluminescence energy associated with the type II recombination was calculated. Depending on the structure, the luminescence energy can shift either blue or red. Using the above calculations, it should be possible to engineer structures that maximize the already large nonlinear effects.
• Henneberger, K., Haug, H., Schafer, W., Binder, R., & Koch, S. W. (1990). Spectral hole burning in active and passive semiconductors. XVII International Conference on Quantum Electronics. Digest of, 118-.
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  Abstract: A many-body nonequilibrium Green's function description of spectral hole burning has been developed. The resulting equations have been solved for active and passive semiconductors. A numerical analysis has been carried out for the stimulated emission of a single-mode under stationary pumping. The results show the spectral hole in the electron distribution and the corresponding line shape of the stimulated emission as a function of pump intensity.
• Olbright, G. R., Fu, W. S., Klem, J., Owyoung, A., Hadley, G. R., Binder, R., Koch, S. W., & Galbraith, I. (1990). Nonlinearities in the absorption and photoluminescence spectra of GaAs/AlAs type II heterostructures. XVII International Conference on Quantum Electronics. Digest of, 124-125.
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  Abstract: The first observation of quasi-steady-state optical nonlinearities in the absorption and photoluminescence (PL) spectra of GaAs/AlAs type-II heterostructures is reported. Deep modulation, ΔT approximately 0.5(Δα = -50,000/cm), due to a >40-meV blue shift and bleaching of the heavy-hole exciton absorption peaks is observed using pump-probe spectroscopy. In addition, a blue shift of up to approximately 10 meV of the indirect PL line is observed with increasing PL excitation intensity. These nonlinearities are understood in terms of spatially separated layers of electrons and holes that are produced by the optical excitation process.
• Schaefer, W., Schuldt, K. -., & Binder, R. (1988). Theory of the optical stark effect in semiconductors. Physica Status Solidi (B) Basic Research, 150(2), 407-412.
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  Abstract: The light-induced changes of the properties of a semiconductor caused by an ultra-short strong laser pulse with a central frequency well below the fundamental absorption edge are investigated. Renormalization and time evolution of one- and two-particle properties are discussed using a nonequilibrium Green's function formalism. Numerical results for the absorption spectra are presented.
• Schäfer, W., Binder, R., & Schuldt, K. H. (1988). The influence of dynamical correlations in semiconductor plasmas on optical spectra. Zeitschrift für Physik B Condensed Matter, 70(2), 145-157.
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  Abstract: On the basis of a nonequilibrium Green's function technique we determine a Bethe-Salpeter equation describing the linear response of a semiconductor under plasma excitation. Dynamical correlations entering the effective screened e-h interaction are treated on the basis of the full RPA polarization function. Numerical results for optical gain and absorption spectra are presented for various temperatures and densities. The validity of the commonly used plasmon pole approximation with regard to the lineshape of optical spectra is critically investigated. © 1988 Springer-Verlag.
• Schäfer, W., Schuldt, K. -., Binder, R., & Treusch, J. (1988). Theory of resonantly excited high-density excition systems. Journal of Luminescence, 40-41(C), 569-570.
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  Abstract: Optical spectra of resonantly excited high density exciton systems, self-consistently calculated on the basis of a recently developed many particle theory, are presented. © 1988.
• Schäfer, W., Binder, R., & Schuldt, K. -. (1987). Time-resolved optical spectra of highly excited semiconductors- theory. Journal of Luminescence, 38(1-6), 282-284.
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  Abstract: Time-resolved measurements of optical spectra of highly excited semiconductors yield a variety of information about fundamental microscopic interaction processes. But up to now experimental results were only interpreted in terms of phenomenological models. A microscopic theory has to treat the evolution of one- and two-particle properties on the time-scale induced by the exciting pulse. Thus a nonequilibrium Bethe-Salpeter equation and a coupled set of Boltzmann equations has to be solved simultaneously. We present numerical results for one-particle distribution functions and absorption spectra for the case of high excitation well below the LO-phonon emission threshold. This leads to the phenomenon of spectral hole burning. © 1987.

Proceedings Publications

• Binder, R. (2023). The polaritonic Bardeen-Cooper-Schrieffer state. In 18th International Conference on Optics of Excitons in Confined Systems (OECS 2023).
• Binder, R. (2023). The polaritonic Bardeen-Cooper-Schrieffer state. In X International Symposium on Ultrafast Dynamics and Ultrafast Bandgap Photonics.
• Binder, R., Luk, S., Kwong, N., Lewandowski, P., Schumacher, S., Lafont, O., Baudin, E., Tignon, J., Lemaitre, A., Bloch, J., Chan, K., & Leung, P. (2017, April). Optical control of polaritons: from optoelectronic to spinoptronic device concepts. In Proceedings of SPIE Defense + Security, Ultrafast Bandgap Photonics II, 10193, 10193-G1 - 10193-G9.
• Luk, S., Lewandowski, P., Kwong, N., Schumacher, S., & Binder, R. (2017, February). Polariton formalism for semiconductor double microcaivities. In Proceedings of SPIE Photonics West, Ultrafast Phenomena and Nanophotonics XXI, 10102-D1 - 10102-D7.
• Binder, R., Lafont, O., Luk, S., Lewandowski, P., Kwong, N., Chan, K., Babilon, M., Leung, P., Gallopin, E., Lemaitre, A., Tignon, J., Schumacher, S., & Baudin, E. (2016, June). Optical control of the optical spin Hall effect. In CLEO.
• Binder, R., Roberts, A., Kwong, N., Sandhu, A. S., & Everitt, H. (2016, Summer). Global k-space analysis of electron-phonon interaction in graphene. In CLEO.
• Binder, R., Tsang, C., Tse, Y., Luk, S., Kwong, N., Chan, K., Leung, P., Lewandowski, P., Schumacher, S., Lafont, O., Baudin, E., & Tignon, J. (2016, December). Formation and all-optical control of optical patterns in semiconductor microcavities. In Proceedings of SPIE, 9835.

Presentations

• Spotnitz, M. E., Kwong, N., & Binder, R. (2023). Terahertz spectroscopy of transition-metal dichalcogenides. American Physical Society March Meeting 2023.
• Binder, R. (2022). Physics of voltage-profile modifications in p-n photodetectors. Conference on Ultrafast Dynamics and Metastability and Ultrafast Bandgap Photonics.
• Binder, R. (2022, August). Exceptional Points in the Fluctuation Modes of a Polariton Laser. 11th International Conference on Spontaneous Coherence in Excitonic Systems (ICSCE-11).
• Binder, R. (2022, June). Goldstone Modes and Soft Fluctuation Modes in Polariton Lasers. VII Conference on Ultrafast Dynamics and Metastability and Ultrafast Bandgap Photonics.
• Spotnitz, M., Kwong, N., & Binder, R. (2022). THz Spectroscopy of semiconductor microcavity lasers. Wyant College of Optical Sciences Industrial Affiliates Workshop.
• Binder, R. (2021). Polariton Lighthouse Effect in Semiconductor Microcavities. OSC Industrial Affiliates Meeting.
• Spotnitz, M., Binder, R., & Kwong, N. (2020, Oct). Theory of THz Spectroscopy of GaAs Microcavity Photon Laser. Wyant College of Optical Sciences Industrial Affiliates Workshop.
• Binder, R., Deng, H., Kwong, N., Hu, J., Wang, Z., Kim, S., & Zhang, B. (2019, April). In Search of a Polaritonic BCS State in Semiconductor Microcavities. Conference on Ultrafast Dynamics and Metastability and Ultrafast Bandgap Photonics. Washington, DC.
• Binder, R., Kwong, N., Hu, J., Wang, Z., Kim, S., Zhang, B., & Deng, H. (2019, Aug). Signatures of a Bardeen-Cooper-Schrieffer Polariton Laser. Conference on Fundamental Optical Properties in Solids. Banff, Canada.
• Hu, J., Wang, Z., Kim, S., Deng, H., Kwong, N., & Binder, R. (2019, Jan). A BCS-like polariton laser. SPIE Photonics West. San Francisco.
• Nenno, D., Schneider, H., & Binder, R. (2019, July). Particle-In-Cell Simulation of Hot-Electron Transport in Normal Metal-Ferromagnet Heterostructures. VLASOVIA: Sixth International Workshop on the Theory and Applications of the Vlasov Equation. Strasbourg, France.
• Binder, R. (2018, Apr). The Graduate Program in Optical Sciences at The University of Arizona. Student recruitment event, CREOL, University of Central Florida. Orlando.
• Binder, R. (2018, Jun). Density and Spin Pattern Control in a Polaritonic Quantum Fluid. Colloquium, University of Kaiserslautern. Kaiserslautern, Germany: University of Kaiserslautern.
• Binder, R. (2018, Jun). Density and Spin Pattern Control in a Polaritonic Quantum Fluid. Special seminar, University of Bayreuth. University of Bayreuth: University of Bayreuth.
• Binder, R., Luk, S., Kwong, N., Lewandowski, P., Schumacher, S., Baudin, E., Tignon, J., Chan, C., & Leung, P. (2018, Apr). Spin and orbital-angular momentum effects in controllable polariton patterns. SPIE Defense + Security - Ultrafast Bandgap Photonics III. Orlando.
• Nenno, D., Choquer, M., Weber, M., Binder, R., & Schneider, H. (2018, Mar). Simulation of Ultrafast Spin-Currents in Optically-Excited Magnetic Multilayers. American Physical Society March Meeting. Los Angeles.
• Binder, R. (2007, November). Optically Induced Non-Equilibrium Phase Transitions of Polaritons in Semiconductor Microcavities. Conference on Ultrafast Dynamics and Metastability. Washington, DC: Georgetown University.
• Binder, R. (2017, September). In memory of Galina Khitrova and Arthur L. Smirl'. Fundamental Optical Processes in Semiconductors (FOPS). Stevenson, WA.
• Binder, R., Luk, S., Kwong, N., Lewandowski, P., Schumacher, S., Lafont, O., Baudin, E., Tignon, J., Lemaitre, A., Bloch, J., Chan, K., & Leung, P. (2017, April). Optical control of polaritons: from optoelectronic to spinoptronic device concepts. SPIE Defense + Security, Ultrafast Bandgap Photonics II. Anaheim, CA: SPIE.
• Binder, R., Luk, S., Lafont, O., Lewandowski, P., Kwong, N., Leung, P., Tignon, J., Schumacher, S., & Baudin, E. (2017, September). Controlling the optical spin Hall effect with light. Fundamental Optical Processes in Semiconductors (FOPS). Stevenson, WA.
• Luk, S., Lewandowski, P., Kwong, N., Schumacher, S., & Binder, R. (2017, February). Polariton formalism for semiconductor double microcaivities. SPIE Photonics West, Ultrafast Phenomena and Nanophotonics XXI.
• Binder, R. (2016, June). Formation and optical control of polaritonic density and spin patterns. University of Dortmund, Germany, Special Seminar.
• Binder, R. (2016, June). Formation and optical control of polaritonic density and spin patterns. University of Munster, Germany, Special Seminar.
• Lafont, O., Lewandowski, P., Luk, S., Kwong, N., Chan, K., Leung, P., Gallopin, E., Lemaitre, A., Roussignal, P., Schumacher, S., Binder, R., Tignon, J., & Baudin, E. (2016, July). Exploring the potential of microcavity polariton physics for photonic devices. 7th International Conference on Metamaterials, Photonic Crystals and Plasmonics.
• Lafont, O., Lewandowski, P., Luk, S., Kwong, N., Chan, K., Leung, P., Gallopin, E., Lemaitre, A., Roussignal, P., Schumacher, S., Binder, R., Tignon, J., & Baudin, E. (2016, June). Exploring the potential of microcavity polariton physics for photonic devices. 24th International Symposium Nanostrauctures Physics and Technology.
• Binder, R. (2015, March). Help, there is a zebra in the quantum fluid!. College of Optical Sciences Colloquium.
• Binder, R., Luk, S., Chan, K., Lewandowski, P., Lafont, O., Ardizzone, V., Baudin, E., Kwong, N., Tse, Y., Luecke, A., Tsang, C., Abbarchi, M., Bloch, J., Gallopin, E., Lemaitre, A., Roussignol, P., Leung, P., Tignon, J., & Schumacher, S. (2015, August). Spinor effects in the pattern formation of polaritons in semiconductor microcavities. SPIE NanoScience+Engineering - Spintronics VIII. San Diego.
• Binder, R., Roberts, A., Kwong, N., Sandhu, A. S., & Everitt, H. (2015, August). Electron-phonon interaction in graphene: a global k-space point of view. Fundamental Optical Processes in Semiconductors (FOPS). Breckenridge, CO.
• Lafont, O., Lewandowski, P., Luk, S., Chan, K., Kwong, N., Bloch, J., Gallopin, E., Lemaitre, A., Leung, P., Binder, R., Schumacher, S., Tignon, J., Roussignol, P., & Baudin, E. (2015, August). Lighthouse effect in a semiconductor microcavity. XXIII Congres General Societe Francaise de Physique. Strasbourg, France.
• Ardizzone, V., Lewandowski, P., Tse, Y. C., Kwong, N. H., Luk, M. H., Luecke, A., Abbarachi, M., Bloch, J., Lemaitre, A., Leung, P. T., Roussignol, P., Binder, R., Tignon, J., & Schumacher, S. (2014, August). Formation and Control of Turing Patterns from Interacting Polaritons in Coupled Semiconductor Microcavities. 32nd International conference on the Physics of Semiconductors (ICPS).
• Binder, R. (2014, December). Exciton interactions in semiconductors: from four-wave mixing to patterns in quantum fluids. CM/AMO Seminar, University of Michigan.
• Binder, R., Kwong, N. H., & Gu, B. (2014, June). Relation between interband dipole and momentum matrix elements in semiconductors. Conference on Lasers and Electro-Optics (CLEO 2014).
• Chan, K. P., Lewandowski, P., Ardizzone, V., Tse, Y. C., Kwong, N. H., Luk, M. H., Luecke, A., Abbarchi, M., Bloch, J., Baudin, E., Galopin, E., Lemaitre, A., Leung, P. T., Roussignol, P., Binder, R., Tignon, J., & Schumacher, S. (2014, March). Controlling Turing Patterns in Spinor Polariton Fluids in Semiconductor Microcavities. American Physical Society March Meeting 2014.
• Gu, B., Kwong, N. H., & Binder, R. (2014, October). Relation between interband dipole and momentum matrix elements in semiconductors. Frontiers in Optics/Laser Science (FiO/LS).
• Luk, M. H., Tsang, C. Y., Lewandowski, P., Tse, Y. C., Kwong, N. H., Luecke, A., Leung, P. T., Binder, R., & Schumacher, S. (2014, March). Secondary instabilities of transverse patterns in a coherent microcavity polariton fluid. American Physical Society March Meeting 2014.
• Roberts, A. T., Binder, R., Kwong, N. H., Golla, D., Cormode, D., LeRoy, B. J., Everitt, H. O., & Sandhu, A. (2014, June). Probing electron-phonon interactions at the saddle point in graphene. Conference on Lasers and Electro-Optics (CLEO 2014).
• Roberts, A. T., Binder, R., Kwong, N. H., Golla, D., Cormode, D., LeRoy, B. J., Everitt, H. O., & Sandhu, A. (2014, October). Probing electron-phonon interactions at the saddle point in graphene. Frontiers in Optics/Laser Science (FiO/LS).
• Tse, Y., Lewandowski, P., Ardizzone, V., Kwong, N., Luk, M., Luecke, A., Abbarachi, M., Bloch, J., Baudin, E., Galopin, E., Lemaitre, A., Tsang, C. Y., Chan, K. P., Leung, P., Roussignol, P., Binder, R., Tignon, J., & Schumacher, S. (2014, October). Control of polariton patterns in semiconductor microcavities. Frontiers in Optics/Laser Science (FiO/LS).
• Tse, Y., Lewandowski, P., Ardizzone, V., Kwong, N., Luk, M., Luecke, A., Abbarchi, M., Bloch, J., Baudin, E., Galopin, E., Lemaitre, A., Tsang, C. Y., Leung, K. P., Roussignol, P., Binder, R., Tignon, J., & Schumacher, S. (2014, June). Control of Turing patterns in a coherent quantum fluid. Conference on Lasers and Electro-Optics (CLEO 2014).

Poster Presentations

• Yuan, M., & Binder, R. (2022). Physics of voltage-profile modifications in p-n photodetectors. Wyant College of Optical Sciences Industrial Affiliates Workshop.
• Binder, R., Lewandowski, P., Lafont, O., Luk, S., Gallopin, E., Lemaitre, A., Bloch, J., Kwong, N., Leung, P., Roussignol, P., Tignon, J., Schumacher, S., & Baudin, E. (2015, August). Polarization dependent four-wave mixing in polariton quantum fluids. Fundamental Optical Processes in Semiconductors (FOPS). Breckenridge, CO.
• Lafont, O., Lewandowski, P., Luk, S., Gallopin, E., Lemaitre, A., Bloch, J., Kwong, N., Leung, P., Binder, R., Roussignol, P., Tignon, J., Schumacher, S., & Baudin, E. (2015, October). Polarization dependent four-wave mixing in polariton quantum fluids. International Conference on Optics of Excitons in Confined Systems (OECS). Jerusalem.