@inproceedings{43189, abstract = {{The nonlinear optical response of quantum well excitons is investigated experimentally using polarization resolved four wave mixing, optical-pump optical-probe, and optical-pump Terahertz-probe spectroscopy. The four-wave mixing data reveal clear signatures of coherent biexcitons which concur with straight-forward polarization selection rules at the Γ point. The type-I samples show the well-established time-domain beating signatures in the transients as well as the corresponding spectral signatures clearly. The latter are also present in type-II samples; however, the smaller exciton and biexciton binding energies in these structures infer longer beating times which, in turn, are accompanied by faster dephasing of the type-II exciton coherences. Furthermore, the THz absorption following spectrally narrow, picosecond excitation at energies in the vicinity of the 1s exciton resonance are discussed. Here, the optical signatures yield the well-established redshifts and blueshifts for the appropriate polarization geometries in type-I quantum well samples also termed “AC Stark Effect”. The THz probe reveals intriguing spectral features which can be ascribed to coherent negative absorption following an excitation into a virtual state for an excitation below the 1s exciton resonance. Furthermore, the scattering and ionization of excitons is discussed for several excitation geometries yielding control rules for elastic and inelastic quasiparticle collisions.}}, author = {{Meier, Torsten and Stein, M. and Schäfer, F. and Anders, D. and Littmann, J. H. and Fey, M. and Trautmann, Alexander and Ngo, C. and Steiner, J. T. and Reichelt, Matthias and Fuchs, C. and Volz, K. and Chatterjee, S.}}, booktitle = {{Ultrafast Phenomena and Nanophotonics XXVII}}, publisher = {{SPIE }}, title = {{{Experimental studies of the excitonic nonlinear response of GaAs-based type-I and type-II quantum well structures interacting with optical and terahertz fields}}}, doi = {{10.1117/12.2650291}}, volume = {{12419}}, year = {{2023}}, } @inproceedings{43190, abstract = {{The nonlinear optical response of quantum well excitons excited by optical fields is analyzed by numerical solutions of the semiconductor Bloch equations. Differential absorption spectra are computed for resonant pumping at the exciton resonance and the dependence of the absorption changes on the polarization directions of the pump and probe pulses is investigated. Coherent biexcitonic many-body correlations are included in our approach up to third-order in the optical fields. Results are presented for spatially-direct type-I and spatiallyindirect type-II quantum well systems. Due to the spatial inhomogeneity, in type-II structures a finite coupling between excitons of opposite spins exists already on the Hartree-Fock level and contributes to the absorption changes for the case of opposite circularly polarized pump and probe pulses.}}, author = {{Meier, Torsten and Trautmann, Alexander and Stein, M. and Schäfer, F. and Anders, D. and Ngo, C. and Steiner, J. T. and Reichelt, Matthias and Chatterjee, S.}}, booktitle = {{Ultrafast Phenomena and Nanophotonics XXVII}}, publisher = {{SPIE}}, title = {{{Analysis of the nonlinear optical response of excitons in type-I and type-II quantum wells including many-body correlations}}}, doi = {{10.1117/12.2650169}}, volume = {{12419}}, year = {{2023}}, } @inproceedings{37329, author = {{Trautmann, Alexander and Zuo, Ruixin and Wang, Guifang and Hannes, Wolf-Rüdiger and Yang, Shidong and Thong, Le Huu and Ngo, Cong and Steiner, Johannes and Ciappina, Marcelo and Reichelt, Matthias and Duc, Huynh Thanh and Song, Xiaohong and Yang, Weifeng and Meier, Torsten}}, booktitle = {{Ultrafast Phenomena and Nanophotonics XXVI}}, editor = {{Betz, Markus and Elezzabi, Abdulhakem Y.}}, title = {{{Microscopic simulations of high harmonic generation from semiconductors}}}, doi = {{10.1117/12.2607447}}, volume = {{11999}}, year = {{2022}}, } @article{37331, abstract = {{High harmonic generation (HHG) from solids shows great application prospects in compact short-wavelength light sources and as a tool for imaging the dynamics in crystals with subnanometer spatial and attosecond temporal resolution. However, the underlying collision dynamics behind solid HHG is still intensively debated and no direct mapping relationship between the collision dynamics with band structure has been built. Here, we show that the electron and its associated hole can be elastically scattered by neighboring atoms when their wavelength approaches the atomic size. We reveal that the elastic scattering of electron/hole from neighboring atoms can dramatically influence the electron recombination with its left-behind hole, which turns out to be the fundamental reason for the anisotropic interband HHG observed recently in bulk crystals. Our findings link the electron/hole backward scattering with Van Hove singularities and forward scattering with critical lines in the band structure and thus build a clear mapping between the band structure and the harmonic spectrum. Our work provides a unifying picture for several seemingly unrelated experimental observations and theoretical predictions, including the anisotropic harmonic emission in MgO, the atomic-like recollision mechanism of solid HHG, and the delocalization of HHG in ZnO. This strongly improved understanding will pave the way for controlling the solid-state HHG and visualizing the structure-dependent electron dynamics in solids.}}, author = {{Zuo, Ruixin and Trautmann, Alexander and Wang, Guifang and Hannes, Wolf-Rüdiger and Yang, Shidong and Song, Xiaohong and Meier, Torsten and Ciappina, Marcelo and Duc, Huynh Thanh and Yang, Weifeng}}, issn = {{2765-8791}}, journal = {{Ultrafast Science}}, publisher = {{American Association for the Advancement of Science (AAAS)}}, title = {{{Neighboring Atom Collisions in Solid-State High Harmonic Generation}}}, doi = {{10.34133/2021/9861923}}, volume = {{2021}}, year = {{2021}}, } @article{20563, author = {{Hannes, W.-R. and Trautmann, Alexander and Stein, M. and Schäfer, F. and Koch, M. and Meier, Torsten}}, journal = {{Physical Review B}}, number = {{7}}, pages = {{075203}}, publisher = {{American Physical Society}}, title = {{{Strongly nonresonant four-wave mixing in semiconductors}}}, doi = {{10.1103/PhysRevB.101.075203}}, volume = {{101}}, year = {{2020}}, } @article{14544, author = {{Vondran, J. and Spitzer, F. and Bayer, M. and Akimov, I. A. and Trautmann, Alexander and Reichelt, Matthias and Meier, Cedrik and Weber, N. and Meier, Torsten and André, R. and Mariette, H.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{15}}, pages = {{155308}}, title = {{{Spatially asymmetric transients of propagating exciton-polariton modes in a planar CdZnTe/CdMgTe guiding structure}}}, doi = {{10.1103/physrevb.100.155308}}, volume = {{100}}, year = {{2019}}, } @article{22887, author = {{Vondran, J. and Spitzer, F. and Bayer, M. and Akimov, I. A. and Trautmann, Alexander and Reichelt, Matthias and Meier, Cedrik and Weber, N. and Meier, Torsten and André, R. and Mariette, H.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{15}}, pages = {{155308}}, title = {{{Spatially asymmetric transients of propagating exciton-polariton modes in a planar CdZnTe/CdMgTe guiding structure}}}, doi = {{10.1103/physrevb.100.155308}}, volume = {{100}}, year = {{2019}}, } @article{13920, abstract = {{We investigate the transient optical response in high-quality Cd0.88Zn0.12Te crystals in the regime of slow light propagation on the lower exciton-polariton branch. Femtosecond photoexcitation leads to very substantial transmission changes in a ∼10-meV broad spectral range within the transparency window of the unexcited semiconductor. These nonlinear optical signatures decay on picosecond time scales governed by carrier thermalization and recombination. The temporal and spectral dependence indicate the dynamical optical response as arising from excitation-induced dephasing and perturbed free induction decay. Model simulations for the optical response taking into account the actual exciton-polariton dispersion and excitation-induced dephasing of a nonlinearly driven two-level system support this interpretation.}}, author = {{Lohrenz, J. and Melzer, S. and Ruppert, C. and Akimov, I. A. and Mariette, H. and Reichelt, Matthias and Trautmann, Alexander and Meier, Torsten and Betz, M.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{7}}, title = {{{Ultrafast dynamical response of the lower exciton-polariton branch in CdZnTe}}}, doi = {{10.1103/physrevb.93.075201}}, volume = {{93}}, year = {{2016}}, }