Nonlinear optical gains in polarization switching of semiconductor lasers

We have numerically studied the nonlinear gain coefficients for the optical fields in parallel and orthogonal polarizations in semiconductor lasers by solving the equation of motion for the density matrix in perturbation series. The electronic band structures and the transition matrix elements used in the calculations are obtained by diagonalizing Luttinger´s Hamiltonian. In the present analysis for InGaAsP lasers, the cross-saturation coefficient for the parallel polarizations is twice as large as the self-saturation. And the cross-saturation coefficient for the orthogonal polarizations, which affects the polarization switching and polarization bistable operations of the laser, rests between the two. The relative magnitude of self-saturation coefficients and cross-saturation coefficients for orthogonal polarizations satisfies the condition for polarization bistable operations