Numerical analysis of the feedback regimes for a single-mode semiconductor laser with external feedback

The effect of external feedback on a single-mode semiconductor laser is estimated by a numerical solution of the nonlinear rate equations. The analysis yields an excellent description of published experimental results. It is found that the lasing mode with the minimum linewidth is most stable rather than the mode with minimum threshold gain. The transition to the coherence-collapse regime is of particular interest. It usually occurs for feedback fractions ≈10^-4, but it can be shifted to considerably larger feedback levels either by increasing the emitted optical power or the laser length or by decreasing the linewidth enhancement factor α