Calculation of the gain saturation in cw semiconductor lasers with Boltzmann kinetics for Coulomb and LO phonon scattering

The characteristics of the photon and carrier densities versus pump current are calculated for a bulk GaAs semiconductor laser including Coulomb and LO phonon scattering in terms of the Boltzmann collision integral. From these characteristics the nonlinear gain compression epsilon is determined as a function of the pump rate. Various Coulomb screening models and their influence on epsilon are discussed. Well above threshold a constant value of epsilon approximately=10-17 cm-3+or-20% is found. The validity of the relaxation time approximations is investigated. Only for high pump powers do the resulting epsilon values of the full kinetics and of relaxation time approximations agree well. Furthermore, the spectral hole burning and the carrier heating in the steady state distributions are calculated.