Analysis of emission and gain saturation in gain-switched semiconductor lasers

We calculate the switch-on dynamics of a single-mode bulk GaAs laser diode including carrier kinetics with Boltzmann collision integrals for carrier-carrier and LO-phonon-carrier scattering. The dependencies of the dynamics on the electrical pump amplitude and on the laser frequency are determined. The shortest light pulse with 12.8 ps (FWHM) is obtained for a laser mode in the gain maximum and a pump rate of 15.5 times the threshold value. The resulting differential gain, transparency density, and gain saturation coefficient are calculated as functions of the pump rate and the mode detuning. The gain saturation during the laser switch-on is enhanced at the trailing edge of the light pulse. This is well described by an extended dynamical gain saturation model that includes correction in terms of the light intensity and its first time derivative. The coefficients of this dynamical gain saturation model are determined by a comparison of the detailed carrier kinetics in a laser with the corresponding rate equations. (C) 1996 Optical Society of America