@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}}, } @inproceedings{43571, abstract = {{We study exciton ionization induced by an axial electric field in a strongly coupled GaAs/Al0.3 Ga0.7 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 lie between the field ionization times of excitons in bulk semiconductors, and in strongly confined quantum well systems.}}, author = {{Meier, Torsten and von Plessen, G. and Koch, M. 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 = {{Proceedings of IV International Conference on Optics of Excitons in Confined Systems}}, location = {{Cortona, Italy}}, pages = {{1759--1762}}, title = {{{Electric-Field-Induced Exciton Ionization in a GaAs/AlGaAs Superlattice}}}, doi = {{10.1007/BF02457276}}, volume = {{17}}, year = {{1995}}, } @inproceedings{44278, abstract = {{Transient four-wave mixing (TFWM) has been extensively used during the last few years to study exciton dynamics in semiconductors and in semiconductor heterostructures. These studies have provided significant insight into exciton dynamics in both ordered and disordered systems. There are, nevertheless, still certain aspects of the excitonic TFWM response that are not completely understood. In particular, a complete understanding of the polarization and intensity dependences of the signai strength, the decay of the time-integrated signal, and the temporal characteristics of the time-resolved signal has proven elusive. Recent theoretical and experimental work has indicated that exciton-exciton interactions are important.1·2 Such interactions include incoherent processes, such as excitation-induced dephasing, and the formation of biexcitons. Additionally, some of the phenomena result from disorder, making them sample dependent.}}, author = {{Meier, Torsten and Albrecht, T.F. and Schulze, A. and Koch, M. and Bott, K. and Feldmann, J. and Stolz, W. and Kuhl, J. and Mayer, E.J. and Koch, S.W. and Göbel, E.O. and Cundiff, S.T.}}, booktitle = {{Quantum Electronics and Laser Science Conference}}, isbn = {{1-55752-402-5}}, location = {{Baltimore, Maryland United States}}, publisher = {{Optical Society of America}}, title = {{{Quantum beats from biexcitons in narrow quantum wells: polarization and density dependence}}}, year = {{1995}}, } @inproceedings{44277, abstract = {{The appearance of quantum beats (QBs) between heavy-hole (hh) and light-hole (lh) excitons in GaAs quantum wells (QWs) has been observed in many degenerate-four- wave-mixing (DFWM) experiments with subpicosecond optical pulses. Although the variation of the beat amplitude and phase with polarization of the incident pulses was recognized early on, a consistent theoretical interpretation of exciton coherence for the case of simultaneous excitation of hh and lh excitons is still missing.}}, author = {{Meier, Torsten and Kuhl, J. and Mayer, E.J. and Smith, G.O. and Bott, K. and Heuckeroth, V. and Thomas, P. and Koch, M. and Hey, R. and Ploog, K.}}, booktitle = {{Quantum Electronics and Laser Science Conference}}, isbn = {{1-55752-402-5}}, location = {{Baltimore, Maryland United States}}, publisher = {{Optical Society of America}}, title = {{{Polarization dependence of quantum beats between light-hole and heavy-hole excitons in GaAs quantum wells}}}, year = {{1995}}, } @article{43593, abstract = {{We study the critical field for the formation of Wannier-Stark ladders and Bloch oscillations in GaAs/AlxGa1−xAs superlattices at low temperatures. From the results of photocurrent and transient four-wave mixing experiments, we conclude that the critical field is higher for superlattices with wide minibands than for superlattices, with narrow minibands. The explanation for this dependence is that intraminiband scattering due to LO-phonon emission is excluded in minibands narrower than the LO-phonon energy.}}, author = {{Meier, Torsten and von Plessen, G. and Feldmann, J. and Göbel, E.O. and Thomas, P. and Goosen, K.W. and Kuo, J.M. and Kopf, R.F.}}, journal = {{Physical Review B}}, number = {{19}}, pages = {{14058--14061}}, publisher = {{American Physical Society}}, title = {{{Influence of scattering on the formation of Wannier-Stark ladders and Bloch oscillations in semiconductor superlattices}}}, doi = {{10.1103/PhysRevB.49.14058}}, volume = {{49}}, year = {{1994}}, } @article{43592, abstract = {{We present a microscopic analysis of coherent effects induced by electric fields in photoexcited semiconductors in the presence of the Coulomb interaction. Both the terahertz emission and four-wave-mixing signals arising from Bloch oscillations in a semiconductor superlattice are computed consistently. It is predicted that Bloch oscillations should be observable also for miniband widths on the order of the exciton binding energy.}}, author = {{Meier, Torsten and von Plessen, G. and Thomas, P. and Koch, S.W.}}, journal = {{Physical Review Letters}}, number = {{6}}, pages = {{902--905}}, publisher = {{American Physical Society}}, title = {{{Coherent electric-field effects in semiconductors}}}, doi = {{10.1103/PhysRevLett.73.902}}, volume = {{73}}, year = {{1994}}, } @inproceedings{43450, abstract = {{The coherent dynamics of exciton wavepackets in (GaIn)As/GaAs as well as (GaIn)As/Ga(PAs) multiple quantum well structures is studied by means of transient four-wave mixing (FWM) experiments. The wavepackets are generated by simultaneous excitation of several exciton transitions with laser pulses of about 100 fs duration. The time-integrated FWM signals exhibit a pronounced modulation superimposed on the overall decay which can be attributed to the quantum interference of the different eigenstates. In the time-resolved FWM signals this interference is not present, reflecting the interplay between many-body Coulomb effects and inhomogeneous broadening. This experimental technique is then employed to extract the exciton binding energies in pseudomorphic symmetrically strained (GaIn)As/GaIPAs) with various In contents.}}, author = {{Meier, Torsten and Koch, M. and Feldmann, J. and Göbel, E.O. and Jahnke, F. and Schäfer, W. and Thomas, P. and Koch, S.W. and Nickel, H. and Luttgen, S. and Stolz, W.}}, booktitle = {{Proceedings der 8. International Winterschool on New Developments in Physics}}, location = {{Mauterndorf}}, number = {{11S}}, pages = {{1965--1971}}, publisher = {{IOP Publishing}}, title = {{{Coherent Dynamics of Exciton Wavepackets in Semiconductor Heterostructures}}}, doi = {{10.1088/0268-1242/9/11S/018}}, volume = {{9}}, year = {{1994}}, } @inbook{43598, abstract = {{Since the realization of semiconductor heterostructures vertical transport of electrically injected carriers has been one of the most interesting topics in semiconductor physics. Precise engineering of semiconductor layers and thus electronic energy levels allows the tailoring of transport properties over a wide range and has even led to the invention of semiconductor devices relying on ballistic electron transport. In addition, negative differential resistance (NDR) can be realized by using tunneling diodes containing double-barrier heterostructures or a superlattice structure.5,6 Actually, the proposal of Esaki and Tsu5 to use electronic Bloch oscillations in the miniband of a semiconductor superlattice to realize NDR marked the starting point for the physics and applications of semiconductor heterostructures.}}, author = {{Meier, Torsten and Feldmann, J. and von Plessen, G. and Thomas, P. and Göbel, E.O. and Goosen, K.W. and Miller, D.A.B. and Cunningham, J.E.}}, booktitle = {{Coherent Optical Interactions in Semiconductors}}, editor = {{Phillips, R.T.}}, isbn = {{978-1-4757-9750-3}}, pages = {{223--244}}, publisher = {{Springer-Science+Business Media}}, title = {{{Vertical transport studied by sub-picosecond four-wave mixing experiments}}}, doi = {{10.1007/978-1-4757-9748-0_10}}, year = {{1994}}, } @inbook{43597, abstract = {{Transient four-wave mixing (TFWM) experiments have been widely used to study the excitation dynamics of excitons in quantum wells [1]. Recently is has been observed that TFWM signals, especially quantum beats between heavy-hole (hh) and light-hole (lh) excitons, strongly depend on the polarization of the incident laser pulses [2–6]. This dependence is presently being investigated.}}, author = {{Meier, Torsten and Bennhardt, D. and Thomas, P. and Hu, Y.Z. and Binder, R. and Koch, S.W.}}, booktitle = {{Coherent Optical Interactions in Semiconductors}}, editor = {{Phillips, R.T.}}, issn = {{978-1-4757-9750-3}}, pages = {{349--354}}, publisher = {{Springer Science+Business Media}}, title = {{{Theory of polarization-dependent four-wave mixing using the optical Bloch equations}}}, doi = {{10.1007/978-1-4757-9748-0_26}}, year = {{1994}}, } @article{43595, abstract = {{A three-pulse degenerate four-wave-mixing experiment and its theoretical analysis reveal contributions of local field and biexciton effects to the nonlinear optical response of the two-dimensional exciton. Quantum beats with a frequency equivalent to the biexciton binding energy appear only for specific polarizations. Polarization-dependent spectrally resolved four-wave mixing shows an additional peak that is separated from the 1s heavy-hole exciton line by the biexciton binding energy. These experimental results are in good agreement with the optical selection rules of the theoretical model, providing evidence for biexcitonic contributions to the four-wave mixing.}}, author = {{Meier, Torsten and Mayer, E.J. and Heuckeroth, V. and Smith, G.O. 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 = {{Physical Review B}}, number = {{19}}, pages = {{14730--14733}}, publisher = {{American Physical Society}}, title = {{{Evidence of Biexcitonic Contributions to Four-wave-mixing in GaAs Quantum Wells}}}, doi = {{10.1103/PhysRevB.50.14730}}, volume = {{50}}, year = {{1994}}, } @article{43594, abstract = {{The effects of disorder and many-body interaction on the four-wave-mixing signal in semiconductor quantum wells are studied experimentally and theoretically. For weakly disordered samples it is shown that the combined influence of Coulomb and disorder effects leads to a characteristic photon-echo signal in time-resolved measurements and to oscillations in the time-integrated signal. Convincing agreement between experiment and theory is demonstrated.}}, author = {{Meier, Torsten and Jahnke, F. and Koch, M. and Feldmann, J. and Schäfer, W. and Thomas, P. and Koch, S.W. and Göbel, E.O. and Nickel, H.}}, journal = {{Physical Review B}}, number = {{11}}, pages = {{8114--8117}}, publisher = {{American Physical Society}}, title = {{{Simultaneous influence of disorder and Coulomb interaction on photon echoes in semiconductors}}}, doi = {{10.1103/PhysRevB.50.8114}}, volume = {{50}}, year = {{1994}}, } @article{43596, author = {{Meier, Torsten and von Plessen, G. and Feldmann, J. and Thomas, P. and Göbel, E.O. and Koch, S.W.}}, journal = {{Optics and Photonics News}}, number = {{12}}, pages = {{20--21}}, publisher = {{Optical Society of America}}, title = {{{Intrinsic perturbations of Bloch oscillations and Wannier Stark ladders in semiconductor superlattices}}}, doi = {{10.1364/OPN.5.12.000020}}, volume = {{5}}, year = {{1994}}, }