Phase coherence of excitons in bulk GaAs

T. Kühn, Eberhard Binder, Fausto Rossi +6 more

Lothar Schultheis, J. Kühl, A. Honold +1 more

The energy levels of Wannier excitons in a thin (≈200-nm) semiconductor layer are quantized because of confinement and are characterized by the wave vector parallel to the layer k║. In contrast to bulk semiconductors, polariton effects which strongly modify the excitonic dispersion curve leading to polariton transport phenomena in a coherent optical experiment are not expected.1 Thus, in an optically thin semiconductor layer, purely excitonic coherence properties can be studied.

R. Hartley, Treena Grevatt, Nicholas Traynor +1 more

Yu. E. Lozovik, I. V. Ovchinnikov, Vladimir A. Sharapov

A theoretical study is reported of stimulated light scattering, including wave-vector reversal and anomalous transmission, by a coherent phase in electron-hole (e-h) systems of low and high charge-carrier density. For these two cases the coherent phase is taken to be a Bose-Einstein condensate of excitons or a BCS-like state of e-h pairs, respectively. The scattering mechanism is laser-induced coherent recombination of two excitons or two coherent e-h pairs, respectively. The e-h system is assumed to exist within a GaAs/AlGaAs double quantum well or bulk GaAs. The emission rate of two photons with antiparallel momenta is estimated. Multiphoton emission due to multiexciton coherent recombination is covered. Methods for detecting the effects predicted are proposed.

Leonid V. Keldysh

Xiangyang Yu, Qi Luo, Wen‐lan Li +3 more

Ultrafast phase dynamics of free-induction decay for carriers in bulk GaAs is studied with differential-phase spectroscopy. The instantaneous phase shifts of the free-induction decay with respect to the excitation pulses are extracted from simultaneously recorded laser pulse autocorrelation and free-induction decay in GaAs. Ultrafast phase dynamics during and immediately after the femtosecond pulse excitation are numerically evaluated with optical Bloch equations using pump pulse and semiconductor exciton parameters as input. Good agreement of the theory with experiment is obtained.