PULSE-PROPAGATION AND CARRIER KINETICS IN LASER-EXCITED SEMICONDUCTORS

Propagation of an intense ultrafast pulse (100 fs) of Gaussian shape with its central frequency above band gap in a GaAs halfspace is investigated theoretically. Nonequilibrium occupation of one particle states, memory effects in the polarization, Coulomb interaction, LO‐phonon Scattering, and spatial inhomogeneities, i. e. the deformation of the pulse shape are taken into account in a strict microscopic approach. The numerical analysis allows to follow the various mechanisms involved on a fs‐time scale, e. g. (1) saturation, spectral hole burning, and relaxation of the one particle distribution, (2) memory effects, dephasing processes, and Coulomb‐enhancement of the polarization and (3) the interplay between that during pulse propagation. The resulting behaviour cannot be simulated by phenomenologically introduced dampings and/or relaxations, thus underlining the importance of accounting for the above mentioned effects in a microscopic way. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA