Dynamics and coherence of a multimode semiconductor laser with optical feedback in an intermediate-length external-cavity regime

We use a traveling-wave numerical model of the temporal dynamics in semiconductor lasers to investigate the dynamics and coherence properties of a multimode semiconductor laser subject to optical feedback. Considering an external cavity of intermediate length, we have observed features characteristic of the so-called short-cavity regime in a region where the relaxation oscillations frequency is larger than the external-cavity frequency. The time scales of the dynamics are controlled in this case by the strength of the optical feedback. We have examined the coherence properties of the multimode emission and have studied how the coherence time is reduced as the laser becomes more multimode.