Abstract

Currently transient optical phenomena in semiconductors are receiving extensive theoretical^[1-3] and experimental^[4-5] attention in connection with recent advances in ultrashort (femtosecond) pulse spectroscopy. For the theoretical description of the evolution of a dense electron-hole plasma in a semiconductor previously excited by strong femtosecond optical pulse one has to consider two different time scales given by τ_s and τ_R. The first one characterizes the relaxation into quasi-equilibrium by the carrier-scattering processes (typically 20 fs - 500 fs), the second one is the recombination lifetime of the electron-hole plasma (typically 0,1 ns - 1 ns). In fact the carrier-scattering processes are determined both by the Coulomb mechanism which conserves the total momentum of an electron-hole system and dominates at high plasma densities and by carrier interaction with any crystal imperfections, i.e. phonons or impurities. In the hydrodynamic regime τ_s < t < τ_R the proposed effect of the strongly anisotropic transient luminescence of the dense electron-hole plasma can exist.

© 1992 IQEC