Theory of hot carrier effects on nonlinear gain in GaAs-GaAlAs lasers and amplifiers

A concise and straightforward model of nonlinear grain based on the carrier heating effect in semiconductor lasers is presented. The problem is formulated using the density matrix approach and includes a priori the effect of free-carrier absorption. Coupled field-medium equations involving photon densities, carrier densities, and carrier temperatures are derived using the results of the density matrix method. The propagation of ultrashort pulses in laser amplifiers is studied and a qualitatively new model along with results on the transient gain recovery dynamics are presented. The model accounts for the wavelength dependence of the asymmetric part of the nonlinear gain observed in direct mixing experiments observed in semiconductor lasers