Dielectric function for a model of laser-excited GaAs - art. no. 075202

We consider a model for the ultrashort pulsed-laser excitation of GaAs in w hich electrons are excited from the top of the valence band to the bottom o f the conduction band. The linear optical response of this excited system i n the visible and near-UV is calculated by solving a statically screened Be the-Salpeter equation. Single-particle electron energies and wave functions are taken from ab initio electronic structure calculations. The screened e lectron-hole interaction W is calculated with a model dielectric function w hich includes the excited carriers. Though band-gap renormalization is negl ected, dramatic changes are observed in the shape of epsilon (2)(omega) due to Pauli blocking and the enhanced screening of W. We estimate the error i ncurred in the static screening approximation by performing static screenin g calculations with the assumption that the excited carriers respond too sl owly to screen W.