Nearly degenerate four-wave mixing in laser diodes with nonuniform longitudinal gain distribution

Nearly degenerate four-wave mixing in above-threshold laser diodes with low or asymmetric facet reflectivities is investigated theoretically. It is shown that the conjugate reflectivity and the four-wave mixing bandwidth are enhanced in lasers with low-reflectivity facets. It is shown, in particular, that the maximum conjugate reflectivity can be obtained in lasers with highly asymmetric facet reflectivities. Longitudinal variations of both the nonlinear interaction and the gain distribution in the laser cavity are taken into account in the model. Such variations are shown to be essential in describing four-wave mixing in laser diodes with low or strongly asymmetric facet reflectivities.