Influence of amplitude-phase coupling on the dynamics of semiconductor lasers subject to optical feedback

We present extensive experimental investigations of the dynamics of semicon ductor lasers subject to optical feedback in dependence on the linewidth en hancement factor Lu which accounts for the amplitude phase coupling of the optical field. A reduction of cu leads to conspicuous changes of the dynami cs of the system which are characterized and classified in the phase space of feedback strength versus injection current, thus demonstrating the impor tance of cu as the system's main nonlinearity. ln particular, we demonstrat e a drastic extension of the regime of coexistence between coherence collap sed dynamics and stable emission, and an increased stability of this stable emission state. We show. that a theoretical analysis of the Lang-Kobayashi rate equation model provides a qualitative understanding of the physical m echanisms underlying thr observed dynamical behavior and its dependence on alpha. Finally, being able to control the nonlinearity of the system, we op en up new perspectives for the stabilization of semiconductor lasers subjec t to moderate to strong optical feedback.