@article{43413, abstract = {{We describe a novel three-pulse degenerate four-wave mixing configuration that permits the direct observation of the coherence between the σ+ and the σ− exciton states in a GaAs quantum well excited in a two-photon process. It is found that the phase coherence between the two single heavy-hole exciton states decays with a time constant that is considerably longer than the dephasing time of the coherence between these states and the ground state (interband coherence). All the experimental data are well described by numerical solutions of the optical Bloch equations for a phenomenological multilevel model.}}, author = {{Meier, Torsten and Bott, K. and Mayer, E.J. and Smith, G.O. and Heuckeroth, V. and Hübner, M. and Kuhl, J. and Schulze, A. and Lindberg, M. and Koch, S.W. and Thomas, P. and Hey, R. and Ploog, K.}}, journal = {{Journal of the Optical Society of America B}}, number = {{5}}, pages = {{1026--1030}}, publisher = {{Optica Publishing Group}}, title = {{{Dephasing of interacting heavy-hole and light-hole excitons in GaAs quantum wells}}}, doi = {{10.1364/JOSAB.13.001026}}, volume = {{13}}, year = {{1996}}, } @inbook{43553, abstract = {{During the last decade, a variety of field-induced coherent phenomena in semiconductor superlattices has received considerable attention both from a theoretical and from an experimental point of view. For the case of a static applied electric field, the existence of Bloch oscillations has been predicted theoretically and confirmed by means of different experimental techniques of nonlinear optical spectroscopy.}}, author = {{Meier, Torsten and Rossi, F. and Je, K.-C and Hader, J. and Thomas, P. and Koch, S.W.}}, booktitle = {{Hot Carriers in Semiconductors}}, editor = {{Hess, K.}}, isbn = {{978-1-4613-8035-1}}, location = {{Chicago}}, pages = {{195--197}}, publisher = {{New York}}, title = {{{On the Observability of dynamic localization in semiconductor superlattices using optical spectroscopy}}}, doi = {{10.1007/978-1-4613-0401-2_46}}, year = {{1996}}, } @inproceedings{43617, author = {{Meier, Torsten and Rossi, F. and Gulia, M. and Selbmann, P.E. and Molinari, E. and Thomas, P. and Thomas, P. and Koch, S.W.}}, booktitle = {{Proceedings of the 23rd ICPS}}, editor = {{Scheffler, M. and Zimmermann, R.}}, location = {{Berlin}}, pages = {{1775--1778}}, publisher = {{World Scientific}}, title = {{{Microscopic theory of the Bloch-oscillation dynamics in semiconductor superlattices: Intra- versus interband Dephasing}}}, year = {{1996}}, } @article{43410, abstract = {{We study exciton ionization induced by an axial electric field in a strongly coupled GaAs/Al0.3Ga0.7 As superlattice at low temperatures. The field-induced ionization times of the heavy-hole 1s exciton in the miniband field regime are determined from transient four-wave-mixing experiments and theoretical model calculations. They are found to decrease with increasing field, and lie in the picosecond and subpicosecond ranges for fields on the order of a few kV/cm. They are considerably longer than those calculated for a 1s exciton in bulk GaAs. We explain this difference as a result of the nonparabolicities in the superlattice miniband dispersion. In addition to studying the field-induced ionization of the 1s resonance, we also investigate the field dependence of excitonic wave packets composed of both bound and continuum states of the exciton. It is found that the continuum components of the wave packet are more sensitive to low electric fields than the 1s component. © 1996 The American Physical Society.}}, author = {{Meier, Torsten and von Plessen, G. and Koch, M. and Feldmann, J. and Thomas, P. and Koch, S.W. and Göbel, E.O. and Goosen, K.W. and Kuo, J.M. and Kopf, R.F.}}, journal = {{Physical Review-Section B-Condensed Matter}}, number = {{20}}, pages = {{13688--13693}}, title = {{{Exciton ionization induced by an electric field in a strongly coupled GaAs/AlxGa1-xAs superlattice}}}, doi = {{10.1103/PhysRevB.53.13688}}, volume = {{53}}, year = {{1996}}, } @article{43416, abstract = {{Beats in the transient four-wave-mixing signal from strongly inhomogeneously broadened semiconductor quantum wells are observed. Based on their phase and polarization properties, the beats are assigned to biexcitons in the mesoscopically disordered material. With increasing excitation intensity a halving of the beat period is observed and is accurately reproduced by calculations including fifth-order contributions.}}, author = {{Meier, Torsten and Albrecht, T.F. and Bott, K. and Schulze, A. and Koch, M. and Cundiff, S.T. and Feldmann, J. and Stolz, W. and Thomas, P. and Koch, S.W. and Göbel, E.O.}}, journal = {{Physical Review B}}, number = {{7}}, pages = {{4436--4439}}, publisher = {{American Physical Society}}, title = {{{Disorder mediated biexcitonic beats in semiconductor quantum wells}}}, doi = {{10.1103/PhysRevB.54.4436}}, volume = {{54}}, year = {{1996}}, } @article{43419, abstract = {{Electronic correlation effects which can be directly probed by ultrafast four-wave mixing are predicted using the electronic-oscillator representation of conjugated polyenes. Comparison with inorganic semiconductors is made possible since the semiconductor Bloch equations projected onto the lowest exciton are obtained as a limiting case. A sign difference in a nonlinear scattering potential clearly shows up in the Wigner spectrogram representing the time and frequency resolved signal.}}, author = {{Meier, Torsten and Mukamel, S.}}, journal = {{Physical review letters}}, number = {{16}}, pages = {{3471--3474}}, publisher = {{American Physical Society}}, title = {{{Femtosecond Spectroscopic Signatures of Electronic Correlations in Conjugated Polyenes and Semiconductor Nanostructures}}}, doi = {{10.1103/PhysRevLett.77.3471}}, volume = {{77}}, year = {{1996}}, } @inbook{43565, abstract = {{The dynamics of carriers induced by electric fields in semiconductor superlattices has received much interest in recent years. Phenomena like Bloch oscillations and negative differential velocity in these structures have been studied using a variety of experimental techniques [1–5]. One particular point of interest has been the transition of the miniband regime to the Bloch oscillation regime with increasing electric field [6,7]. Cw spectra of strongly-coupled superlattices have evidenced that this transition is concomitant with a rapid field-induced ionization of the zero-field miniband exciton [5,8]. While it has been pointed out from the theoretical side that the field-induced ionization process strongly influences the coherent dynamics in the transition region [9], no systematic experimental investigation of the ionization process has been carried out so far. One interesting question that such an investigation could help to answer is to what extent this ionization process differs from the well-documented case of field-induced exciton ionization in bulk semiconductors.}}, author = {{Meier, Torsten and Koch, M. and von Plessen, G. and Feldmann, J. and Koch, S.W. and Thomas, P. and Göbel, E.O. and Goosen, K.W. and Kuo, J.M. and Kopf, R.F.}}, booktitle = {{Hot Carriers in Semiconductors}}, editor = {{Hess, K.}}, isbn = {{10.1007/978-1-4613-0401-2_1}}, location = {{Chicago}}, pages = {{3--6}}, publisher = {{Plenum Press}}, title = {{{Field-induced exciton ionization studied by four-wave mixing}}}, doi = {{10.1007/978-1-4613-0401-2_1}}, year = {{1996}}, } @inbook{43615, author = {{Meier, Torsten and Koch, S.W. and Hader, J. and Je, K.-C and Rossi, F. and Thomas, P.}}, booktitle = {{Frontiers in Nanoscale Science of Micro/Submicro Devices}}, editor = {{Jauho, A.-P. and Buzeaneva, E.V.}}, isbn = {{9780792343011}}, location = {{Kiev}}, pages = {{459--478}}, publisher = {{Kluver Publ.}}, title = {{{Equilibrium and nonequilibrium optical effetcs in semiconductor heterostructures}}}, volume = {{328}}, year = {{1996}}, } @inbook{43559, abstract = {{The progress in the generation of ultrashort laser pulses, together with the development of spectroscopies on this time-scale, has led to a series of experiments which give new insight into the microscopic carrier dynamics in semiconductors. In particular, the energy relaxation of photoexcited carriers has been widely investigated. At the same time, recent progress in the fabrication and characterization of semiconductor heterostructures and superlattices allows a detailed study of a new class of phenomena induced by an applied electric field, such as Bloch oscillations1,2. Both classes of phenomena typically occur on a pico- or femtosecond time-scale, where the coupling between coherent and incoherent phenomena is known to play a dominant role3. Therefore, an adequate theoretical model of the ultrafast dynamics on this time-scale must account for both coherent and incoherent effects on the same kinetic level.}}, author = {{Meier, Torsten and Rossi, F. and Thomas, P. and Koch, S.W. and Selbmann , P.E. and Molinari, E.}}, booktitle = {{Hot Carriers in Semiconductors}}, editor = {{Hess, K.}}, isbn = {{978-1-4613-8035-1}}, location = {{Chicago}}, pages = {{157--160}}, publisher = {{Plenum Press}}, title = {{{Phonon-Induced Suppression of Bloch Oscillations in Semiconductor Superlattices: a Monte Carlo Investigation}}}, doi = {{10.1007/978-1-4613-0401-2_37}}, year = {{1996}}, } @article{43578, abstract = {{Coherent effects are analyzed that are induced by homogeneous electric fields in photoexcited semiconductors. Extended semiconductor Bloch equations are presented, which include the applied electric field, in addition to the many-body Coulomb contributions in the time-dependent Hartree-Fock approximation. These equations are solved for a one-dimensional tight-binding model of a semiconductor superlattice. Linear and nonlinear optical signals associated with the coherent field-induced effects are calculated. For the case of a static electric field, the influence of the Coulomb interaction, which is treated on the Hartree-Fock level for a contact potential approximation, on the Bloch oscillations, and on their counterpart in the frequency domain, the Wannier-Stark-ladder, is analyzed. For a time-dependent electric field, dynamic localization, i.e., the localization of electrons due to an oscillating electric field, is analyzed. It is predicted that the dynamic localization should be observable in semiconductor superlattices even in the presence of Coulomb interaction.}}, author = {{Meier, Torsten and von Plessen, G. and Thomas, P. and Koch, S.W.}}, journal = {{Physical Review B}}, number = {{20}}, pages = {{14490--14497}}, publisher = {{American Physical Society}}, title = {{{Coherent effects induced by static and time-dependent electric fields in semiconductors}}}, doi = {{10.1103/PhysRevB.51.14490}}, volume = {{51}}, year = {{1995}}, } @article{43586, abstract = {{We report results on selection rules and polarization conditions for quantum beating between light hole and heavy hole excitons in GaAs quantum wells. The measurements were conducted using time-integrated degenerate-four-wave-mixing in a three-pulse configuration. By choosing particular polarization configurations of the ultrashort optical pulses exciting heavy and light hole excitons simultaneously, degenerate four-wave-mixing signals show either quantum beating or no modulation at all. The experiments are analyzed using a model that takes into account exciton/exciton interaction.}}, author = {{Meier, Torsten and Smith, G.O. and Mayer, E.J. and Heuckeroth, V. and Kuhl, J. and Bott, K. and Schulze, A. and Bennhardt, D. and Koch, S.W. and Thomas, P. and Hey, R. and Ploog, K.}}, journal = {{Solid state communications}}, number = {{5}}, pages = {{373--377}}, publisher = {{Pergamon}}, title = {{{Polarization selection rules for quantum beating between light-and heavy-hole excitons in GaAs quantum wells}}}, doi = {{10.1016/0038-1098(95)00052-6}}, volume = {{94}}, year = {{1995}}, } @article{43590, abstract = {{The effective dimensionality of excitons can be drastically changed by applying an alternating electric field. On the basis of a full three-dimensional description of both coherent and incoherent phenomena in anisotropic structures it is found that appropriate applied oscillating fields change the exciton wave function from anisotropic three dimensional to basically two dimensional. This effective-dimension change is caused by dynamic localization which leads to an increase of the exciton binding energy and of the corresponding oscillator strength.}}, author = {{Meier, Torsten and Rossi, F. and Thomas, P. and Koch, S.W.}}, journal = {{Physical review letters}}, number = {{13}}, pages = {{2558--2561}}, publisher = {{American Physical Society}}, title = {{{Dynamic Localization in Anisotropic Coulomb Systems: Field induced Crossover of the Exciton Dimension}}}, doi = {{10.1103/PhysRevLett.75.2558}}, volume = {{75}}, year = {{1995}}, } @article{43591, abstract = {{Quasiequilibrium nonlinear optical absorption spectra are computed for semiconductor superlattices. The theory generalizes the semiconductor Bloch equations to describe anisotropic structures. The equation for the interband polarization is solved numerically and the carrier‐density dependent optical nonlinearities are computed. Starting from excitonic absorption, with increasing density exciton saturation and the development of gain is observed. The dependence of the gain spectra on structural parameters of the superlattice is discussed.}}, author = {{Meier, Torsten and Je, K.-C and Rossi, F. and Koch, S.W.}}, journal = {{Applied physics letters}}, number = {{20}}, pages = {{2978--2980}}, publisher = {{American Institute of Physics}}, title = {{{Theory of quasi-equilibrium nonlinear optical absorption in semiconductor superlattices}}}, doi = {{10.1063/1.114831}}, volume = {{67}}, year = {{1995}}, } @article{43589, author = {{Meier, Torsten and Kuhl, J. and Mayer, E.J. and Smith, G.O. and Bott, K. and Schulze, A. and Heuckeroth, V. and Heller, O. and Cundiff, S.T. and Bennhardt, D. and Koch, S.W. and Thomas, P. and Hey, R. and Ploog, K.}}, journal = {{Laser Physics}}, number = {{3}}, pages = {{616--620}}, publisher = {{INTERPERIODICA}}, title = {{{Transient degenerate four-wave-mixing on excitons in GaAs quantum wells}}}, volume = {{5}}, year = {{1995}}, } @inproceedings{43604, author = {{Meier, Torsten and Kuhl, J. and Mayer, E.J. and Smith, G.O. and Schulze, A. and Bennhardt, D. and Koch, S.W. and Thomas, P. and Hey, R. and Ploog, K.}}, booktitle = {{Proceedings of the 22nd International Conference on the Physics of Semiconductors ICPS}}, editor = {{Lockwood, D.J.}}, location = {{Vancouver, Canada}}, pages = {{1776--1779}}, publisher = {{World Scientific}}, title = {{{Biexciton Contributions to the Excitonic Nonlinearity in GaAs Quantum Wells}}}, year = {{1995}}, } @inproceedings{43451, author = {{Meier, Torsten and Feldmann, J. and Koch, M. and von Plessen, G. and Stolz, W. and Thomas, P. and Göbel, E.O.}}, booktitle = {{Proceedings of the 22nd International Conference on the Physics of Semiconductors ICPS}}, editor = {{Lockwood, D.J.}}, location = {{Vancouver, Canada}}, pages = {{1296--1303}}, publisher = {{World Scientific}}, title = {{{Coherent dynamics of exciton wave packets in quantum wells and superlattices}}}, year = {{1995}}, } @article{43452, abstract = {{We report time-resolved degenerate four-wave-mixing experiments on a high-quality single GaAs quantum well. The signals for parallel and cross-polarized exciting pulses show pronounced quantum beats with different frequencies corresponding to the heavy/light-hole splitting and the biexciton binding energy, respectively. Comparison of the experimental data with solutions of the optical Bloch equations for a phenomenological model system shows that these features result from strong contributions of the biexcitonic state. The importance of biexcitons to the nonlinear coherent response of the two-dimension exciton is further confirmed by the frequency dependence of the time-integrated four-wave-mixing signal amplitudes measured for the two polarization geometries.}}, author = {{Meier, Torsten and Mayer, E.J. and Smith, G.O. and Heuckeroth, V. and Kuhl, J. and Bott, K. and Schulze, A. and Koch, S.W. and Thomas, P. and Hey, R. and Ploog, K.}}, journal = {{Physical Review B}}, number = {{16}}, pages = {{10909--10914}}, publisher = {{American Physical Society}}, title = {{{Polarization dependence of beating phenomena at the energetically lowest exciton transition in GaAs quantum wells}}}, doi = {{10.1103/PhysRevB.51.10909}}, volume = {{51}}, year = {{1995}}, } @article{43581, abstract = {{The ultrafast dynamics of photoexcited carriers in semiconductor superlattices is studied theoretically on the basis of a Monte Carlo solution of the coupled Boltzmann transport equations for electrons and holes. The approach allows a kinetic description of the relevant interaction mechanisms such as intra- miniband and interminiband carrier-phonon scattering processes. The energy relaxation of photoexcited carriers, as well as their vertical transport, is investigated in detail. The effects of the multiminiband nature of the superlattice spectrum on the energy relaxation process are discussed with particular emphasis on the presence of Bloch oscillations induced by an external electric field. The analysis is performed for different superlattice structures and excitation conditions. It shows the dominant role of carrier–polar-optical-phonon interaction in determining the nature of the carrier dynamics in the low-density limit. In particular, the miniband width, compared to the phonon energy, turns out to be a relevant quantity in predicting the existence of Bloch oscillations.}}, author = {{Meier, Torsten and Rossi, F. and Thomas, P. and Koch, S.W. and Selbmann, P.E. and Molinari, E.}}, journal = {{Physical Review B}}, number = {{23}}, pages = {{16943--16953}}, publisher = {{American Physical Society}}, title = {{{Ultrafast carrier relaxation and vertical-transport phenomena in semiconductor superlattices: A Monte Carlo analysis}}}, doi = {{10.1103/PhysRevB.51.16943}}, volume = {{51}}, year = {{1995}}, } @article{43575, abstract = {{Optical transitions into discrete levels coupled to an optically active continuum lead to asymmetrical Fano lines in the linear absorption spectra, reflecting interference between the excitation channels. We investigate the corresponding four-wave-mixing spectra for the nonlinear optical response within a model of noninteracting electrons. Our results show that four-wave-mixing experiments provide a useful tool to identify Fano resonances.}}, author = {{Meier, Torsten and Schulze, A. and Thomas, P. and Vaupel, H. and Maschke, K.}}, journal = {{Physical Review B}}, number = {{20}}, pages = {{13977--13986}}, publisher = {{American Physical Society}}, title = {{{Signatures of Fano-resonances in four-wave mixing experiments}}}, doi = {{10.1103/PhysRevB.51.13977}}, volume = {{51}}, year = {{1995}}, } @inproceedings{43568, abstract = {{The effective dimensionality of excitons can be drastically changed by applying an alternating electric field. On the basis of a full three-dimensional description of both coherent and incoherent phenomena in anisotropic structures it is found that appropriate applied oscillating fields change the exciton wave function from anisotropic three dimensional to basically two dimensional. This effective-dimension change is caused by dynamic localization which leads to an increase of the exciton binding energy and of the corresponding oscillator strength.}}, author = {{Meier, Torsten and Rossi, F. and Je, K.-C and Hader, J. and Thomas, P. and Koch, S.W.}}, booktitle = {{Proceedings of IV International Conference on Optics of Excitons in Confined Systems}}, location = {{Cortona, Italy}}, pages = {{1693--1697}}, publisher = {{Kluwer Academic Publishers}}, title = {{{Linear and Non-linear Optical Properties of Semiconductor Superlattices: Excitonic and Field-Induced Effects}}}, doi = {{10.1007/BF02457265}}, volume = {{17}}, year = {{1995}}, }