Nearly degenerate four-wave mixing in laser diodes subject to strong probe injection power

Nearly degenerate four-wave mixing (FWM) in above-threshold laser diodes with symmetric or asymmetric facet reflectivities, subject to strong probe injection power, is investigated theoretically, taking into account the effects of pump depletion, carrier diffusion, gain saturation, gain compression, total power dependence of the gain and coupling coefficients as well as the longitudinal dependence of the nonlinear interaction. It is shown that the reflectivity efficiencies of probe and conjugate waves demonstrate significantly different behaviors for strong probe injection power, compared to small probe injection power, and a greater than 3 dB enhancement of reflectivity efficiencies can be achieved in an asymmetric laser diode, compared to a symmetric laser.