Carrier diffusion and depletion effects on multiwave mixing in semiconductor lasers

A detailed theoretical treatment has been undertaken of multiwave mixing in semiconductor lasers, taking into account the effects of pump/probe depletion, carrier diffusion, usual gain saturation, nonlinear gain compression, total power dependence of the coupling coefficients as well as the longitudinal dependence of the nonlinear interaction. It is shown that the effect of carrier diffusion can considerably enhance the probe and conjugate reflectivity for detuning frequency near the relaxation oscillation frequency of the pump laser. It is demonstrated, in particular that, for relatively high input probe power, the probe and conjugate reflectivity can be enhanced significantly near the relaxation oscillation frequency of the pump laser, compared to that for low input probe power. Furthermore, both the probe reflectivity and the conjugate reflectivity show asymmetric characteristics with respect to the zero pump/probe frequency detunings. The pump/probe depletion effect plays an important role in determining the optical output power when the input probe power is larger than ~0.1 μW