Dynamics of semiconductor lasers with optical feedback: Comparison of multimode models in the low-frequency fluctuation regime

The role of spontaneous emission noise and gain line profile in the dynamics of a multimode semiconductor laser with weak-to-moderate optical feedback is studied. Two models of such a laser are compared. If the gain profile is flat and in the absence of noise, model A predicts that all modal intensities are in phase, and model B predicts antiphase dynamics of the modal intensities. Noise induces out-of-phase solutions in model A and hardly affects model B. Weakly curved gain profile determines the number of lasing modes but otherwise has little effect on the laser dynamics in both models