@article{43328, abstract = {{Intraband emission resulting from the second-order polarization induced by a femtosecond pump field in semiconductor nanostructures is calculated. The two-band model is transformed to the exciton representation, and exciton-phonon coupling represented by arbitrary spectral densities is incorporated into the equations of motion for the relevant exciton variables through Redfield superoperators. Time-resolved coherent and incoherent terahertz radiation as well as the incoherent optical fluorescence are calculated for a one-dimensional model of coupled quantum wells in an external electric field with on-site Coulomb interaction between electrons and holes and an overdamped Brownian oscillator spectral density representing the electron-phonon coupling. A doorway-window picture based on the reduced single-electron density matrix is developed for the analysis of both signals. Disorder and phonon-induced dephasing effects on the various signals are discussed and compared.}}, author = {{Meier, Torsten and Zhang, W.M. and Chernyak, V. and Mukamel, S.}}, journal = {{Physical Review B}}, number = {{4}}, publisher = {{American Physical Society}}, title = {{{Intraband terahertz emission from coupled semiconductor quantum wells: A model study using the exciton representation}}}, doi = {{10.1103/PhysRevB.60.2599}}, volume = {{60}}, year = {{1999}}, } @article{43329, abstract = {{Frequency mixing ( 2ω1−ω2) is demonstrated in femtosecond nondegenerate four-wave mixing (FWM) on GaAs multiple quantum wells using two synchronized, independently tunable lasers. The frequency mixing component in the spectrally resolved FWM coexists with the exciton resonance, and it dominates over the exciton component at high intensity and high detuning. This off-resonant component is present only for delays smaller than the temporal pulse width, whereas the resonant exciton component survives for longer delays.}}, author = {{Meier, Torsten and Ahn, Y. H. and Yahng, J. S. and Sohn, J. Y. and Yee, K. J. and Hohng, S. C. and Woo, J. C. and Kim, D. S. and Koch, S.W. and Lim, Y. S. and Kim, E. K.}}, journal = {{Physical review letters}}, number = {{19}}, publisher = {{American Physical Society}}, title = {{{From exciton resonance to frequency mixing in GaAs multiple quantum wells}}}, doi = {{10.1103/PhysRevLett.82.3879}}, volume = {{82}}, year = {{1999}}, } @article{43330, abstract = {{Differential absorption spectra of high-quality InGaAs quantum wells are presented for various pump detunings and polarization configurations. For low intensity pump pulses tuned well below the exciton a redshift is observed for opposite circularly polarized probe pulses. Microscopic calculations show that this redshift originates from memory effects in the Coulomb-induced excitonic correlations.}}, author = {{Meier, Torsten and Sieh, C. and Jahnke, F. and Knorr, A. and Koch, S.W. and Brick, P. and Hübner, M. and Ell, C. and Prineas, J. and Khitrova, G. and Gibbs, H.M.}}, journal = {{Physical review letters}}, number = {{15}}, publisher = {{American Physical Society}}, title = {{{Coulomb memory signatures in the excitonic optical Stark effect}}}, doi = {{10.1103/PhysRevLett.82.3112}}, volume = {{82}}, year = {{1999}}, } @article{43331, abstract = {{A new spectroscopic technique is demonstrated on three characteristically different semiconductor quantum-well samples. Coherent excitation spectroscopy reveals coherent coupling and effectively suppresses the signatures of inhomogeneous broadening and incoherent transfer between various excitonic states in quantum wells. Coherently coupled homogeneous subsystems are analyzed in an inhomogeneously broadened excitonic ensemble.}}, author = {{Meier, Torsten and Euteneuer, A. and Finger, E. and Hofmann, M. and Stolz, W. and Thomas, P. and Koch, S.W. and Rühle, W.W. and Hey, R. and Ploog, K.}}, journal = {{Physical review letters}}, number = {{10}}, publisher = {{American Physical Society}}, title = {{{Coherent excitation spectroscopy on inhomogeneous exciton ensembles}}}, doi = {{10.1103/PhysRevLett.83.2073}}, volume = {{83}}, year = {{1999}}, } @article{43326, abstract = {{The distribution of cooperative radiative decay rates in photosynthetic aggregates is calculated using a Frenkel exciton model with static diagonal disorder. This distribution which depends on both the exciton coherence sizes and the aggregate geometry can be directly observed using single-molecule spectroscopy. Comparison is made with a dynamic exciton self-trapping (polaron) mechanism for localization.}}, author = {{Meier, Torsten and Zhao, Y. and Zhang, W.M. and Chernyak, V. and Mukamel, S.}}, journal = {{The Journal of Physical Chemistry B}}, number = {{19}}, pages = {{3954--3962}}, publisher = {{American Chemical Society}}, title = {{{Superradiance Coherence Sizes in Single-Molecule Spektroscopy of LH2 Antenna Complexes}}}, doi = {{10.1021/jp990140z}}, volume = {{103}}, year = {{1999}}, } @article{43327, abstract = {{Absorption changes in semiconductors induced by low-density populations are calculated using a one-dimensional model. The microscopic analysis includes Coulomb-induced many-body correlations and reveals distinct signatures of six particle correlations. The strength of exciton bleaching induced by excitons and electron-hole pairs is compared and analyzed.}}, author = {{Meier, Torsten and Koch, S.W.}}, journal = {{Physical Review B}}, number = {{20}}, publisher = {{American Physical Society}}, title = {{{Excitons versus unbound electron-hole pairs and their influence on exciton bleaching: A model study}}}, doi = {{10.1103/PhysRevB.59.13202}}, volume = {{59}}, year = {{1999}}, } @article{43325, abstract = {{Nonlinear exciton equations for one- and two-exciton variables, obtained by mapping the two-band model onto the molecular (Frenkel) Hamiltonian, are applied to calculate resonant optical nonlinearities in two-dimensional semiconductors in a strong perpendicular magnetic field. The polarization dependence of the time-resolved four-wave-mixing signals provides a direct probe for the two-exciton manifold as well as for the asymmetry of the particle-particle and particle-hole Coulomb interactions.}}, author = {{Meier, Torsten and Yokojima, S. and Chernyak, V. and Mukamel, S.}}, journal = {{Physical Review B}}, number = {{19}}, title = {{{Femtosecond four-wave-mixing spectroscopy of interacting magnetoexcitons in semiconductor quantum wells}}}, doi = {{10.1103/PhysRevB.59.12584}}, volume = {{59}}, year = {{1999}}, } @inproceedings{44272, abstract = {{A microscope many-body theory for the nonlinear optical response of semiconductors is reviewed. The importance of Coulomb interaction induced carrier correlations is demonstrated in excitonic pump-probe spectra. The influence of excitonic and biexcitonic contributions to coherent pump- induced absorption changes at the exciton frequency are discussed. Absorption changes induced by incoherent exciton and unbound electron-hole populations are studied.}}, author = {{Meier, Torsten and Koch, S.W.}}, booktitle = {{Photonic Systems and Applications in Defense and Manufacturing}}, pages = {{24--35}}, publisher = {{SPIE}}, title = {{{Optical linearities in semiconductors}}}, doi = {{10.1117/12.368481}}, volume = {{3898}}, year = {{1999}}, } @inproceedings{44273, abstract = {{It is demonstrated that the optical response of semiconductor systems is influenced by various interactions. In detail, it is shown that meaningful calculations of optical nonlinearities in semiconductor structures require to microscopically include Coulomb-induced many-body carrier-correlations. Some distinct signatures induced by correlations in nonlinear optical signals are presented and discussed.}}, author = {{Meier, Torsten and Jahnke, F. and Koch, S.W.}}, booktitle = {{Technical Digest. CLEO/Pacific Rim'99. Pacific Rim Conference on Lasers and Electro-Optics}}, isbn = {{0-7803-5661-6}}, location = {{Seoul, Korea (South)}}, pages = {{632--633}}, publisher = {{IEEE}}, title = {{{Optical nonlinearities in semiconductor quantum-well and microcavity structures}}}, doi = {{10.1109/CLEOPR.1999.817755}}, volume = {{3}}, year = {{1999}}, } @article{13765, abstract = {{ We calculate the reflectance anisotropy for GaP(001)(2×4) surfaces using a real-space multigrid method and ab initio pseudopotentials. Our results obtained within DFT-LDA show good qualitative agreement with recent experiments. This holds in particular for the stoichiometric trends. A strong negative anisotropy at low photon energies is linked to the formation of Ga–Ga bonds along the [110] direction. There are discrepancies, however, with respect to the line shape and the energetic positions of characteristic peaks. Substantial improvement is achieved by using a numerically efficient GW approach with approximations for local-field effects and dynamical screening. We find that the spectral features related to transitions between surface perturbed bulk wave functions are more strongly affected by self-energy corrections than anisotropies directly linked to surface electronic states. }}, author = {{Schmidt, Wolf Gero and FATTEBERT, J. L. and BERNHOLC, J. and BECHSTEDT, F.}}, issn = {{0218-625X}}, journal = {{Surface Review and Letters}}, number = {{6}}, pages = {{1159--1165}}, title = {{{SELF-ENERGY EFFECTS IN THE OPTICAL ANISOTROPY OF GaP(001)}}}, doi = {{10.1142/s0218625x99001281}}, volume = {{6}}, year = {{1999}}, } @article{13768, author = {{Frisch, A. M. and Schmidt, Wolf Gero and Bernholc, J. and Pristovsek, M. and Esser, N. and Richter, W.}}, issn = {{0163-1829}}, journal = {{Physical Review B}}, number = {{4}}, pages = {{2488--2494}}, title = {{{(2×4)GaP(001) surface: Atomic structure and optical anisotropy}}}, doi = {{10.1103/physrevb.60.2488}}, volume = {{60}}, year = {{1999}}, } @article{13766, author = {{Bechstedt, F. and Pulci, O. and Schmidt, Wolf Gero}}, issn = {{0031-8965}}, journal = {{physica status solidi (a)}}, number = {{5}}, pages = {{5--16}}, title = {{{Theoretical Aspects of the Optical Response of Semiconductor Surfaces}}}, doi = {{10.1002/(sici)1521-396x(199909)175:1<5::aid-pssa5>3.0.co;2-9}}, volume = {{175}}, year = {{1999}}, } @article{13769, author = {{Schmidt, Wolf Gero and Briggs, E. L. and Bernholc, J. and Bechstedt, F.}}, issn = {{0163-1829}}, journal = {{Physical Review B}}, number = {{3}}, pages = {{2234--2239}}, title = {{{Structural fingerprints in the reflectance anisotropy spectra ofInP(001)(2×4)surfaces}}}, doi = {{10.1103/physrevb.59.2234}}, volume = {{59}}, year = {{1999}}, } @article{13767, author = {{Esser, N. and Schmidt, Wolf Gero and Bernholc, J. and Frisch, A. M. and Vogt, P. and Zorn, M. and Pristovsek, M. and Richter, W. and Bechstedt, F. and Hannappel, Th. and Visbeck, S.}}, issn = {{0734-211X}}, journal = {{Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures}}, number = {{4}}, title = {{{GaP(001) and InP(001): Reflectance anisotropy and surface geometry}}}, doi = {{10.1116/1.590810}}, volume = {{17}}, year = {{1999}}, } @article{13764, author = {{Bechstedt, F. and Adolph, B. and Schmidt, Wolf Gero}}, issn = {{0103-9733}}, journal = {{Brazilian Journal of Physics}}, number = {{4}}, title = {{{Ab initio calculation of linear and nonlinear optical properties of semiconductor structures}}}, doi = {{10.1590/s0103-97331999000400007}}, volume = {{29}}, year = {{1999}}, } @inproceedings{43335, abstract = {{A microscopic many-body theory is presented which allows one to compute the linear and nonlinear optical properties of semiconductor superlattices in the presence of static and time-dependent electric fields applied in the growth direction. For static fields the Bloch-oscillation dynamics, the role of Coulomb effects, carrier relaxation, phonon scattering, and inter- and intraband polarization dephasing is analyzed. The observability of dynamic localization using optical spectroscopy is discussed for alternating applied fields.}}, author = {{Meier, Torsten and Je, K.-C and Rossi, F. and Hader, J. and Thomas, P. and Koch, S.W.}}, booktitle = {{Ultrafast Phenomena in Semiconductors II}}, pages = {{20--27}}, publisher = {{SPIE}}, title = {{{Coherent electric-field effects in semiconductors}}}, doi = {{10.1117/12.306150}}, volume = {{3277}}, year = {{1998}}, } @article{43338, abstract = {{A theory for four-wave-mixing signals from molecular aggregates, which includes effects of two-exciton states, static disorder, and coupling to a phonon bath with an arbitrary spectral density, is developed. The third-order polarization is rigorously partitioned into a coherent and a sequential contribution. The latter is given by a sum of an exciton-hopping and a ground state (bleaching) terms, both expressed using the doorway-window representation. Applications are made to photon-echo and pump-probe spectroscopies of the B850 system of the LH2 antenna in purple bacteria.}}, author = {{Meier, Torsten and Zhang, W.M. and Chernyak, V. and Mukamel, S.}}, journal = {{The Journal of chemical physics}}, number = {{18}}, pages = {{7763--7774}}, publisher = {{American Institute of Physics}}, title = {{{Exciton-Migration and Three-Pulse Femtosecond Optical Spectroscopies of Photosynthetic Antenna Complexes}}}, doi = {{10.1063/1.476212}}, volume = {{108}}, year = {{1998}}, } @article{43337, abstract = {{Femtosecond spectroscopies of chlorophyll dimers and the LH2 antenna complex are calculated using a theory that incorporates the effects of two–exciton states, static disorder and coupling of excitons to phonons with an arbitrary spectral density. Applications are made to pump–probe and echo peak–shift measurements in the B820 dimers, and to fluorescence depolarization in the B850 system of the LH2 antenna of purple bacteria.}}, author = {{Meier, Torsten and Zhang, W.M. and Chernyak, V. and Mukamel, S.}}, journal = {{Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences}}, number = {{1736}}, pages = {{405--419}}, publisher = {{The Royal Society}}, title = {{{Simulation of Three-Pulse-Echo and Fluorescence Depolarization in Photosynthetic Aggregates}}}, doi = {{10.1098/rsta.1998.0173}}, volume = {{356}}, year = {{1998}}, } @article{43336, abstract = {{We investigate the nonlinear dynamics of the composite absorber-cavity system by performing femtosecond time-resolved four-wave mixing experiments on a semiconductor microcavity. The nonlinear response exhibits an unexpected temporal behavior that distinctively differs from that of other multilevel systems. Accompanying model calculations show that the observed behavior is a direct consequence of the mixed electron-photon character of the absorber-cavity system.}}, author = {{Meier, Torsten and Koch, M. and Shah, J.}}, journal = {{Physical Review B}}, number = {{4}}, pages = {{2049--2052}}, publisher = {{American Physical Society}}, title = {{{Coupled absorber-cavity system: Observation of a characteristic nonlinear response}}}, doi = {{10.1103/PhysRevB.57.R2049}}, volume = {{57}}, year = {{1998}}, } @article{43339, author = {{Meier, Torsten and Thomas, P. and Koch, S.W.}}, journal = {{Physics of Low-Dimensional Structures (PLDS)}}, number = {{3-4}}, pages = {{1--44}}, title = {{{Coherent Effects in Photoexcited Semiconductor Superlattices with Electric Fields}}}, volume = {{1998}}, year = {{1998}}, }