Stability and dynamical properties of the coexisting attractors of an external-cavity semiconductor laser

Coexisting attractors, which arise from different external-cavity modes of the same longitudinal mode of the solitary laser, retain distinct stability properties, particularly when the laser is biased far above threshold and subjected to moderately strong optical feedback from a distant reflector. When the laser is modeled by the Lang and Kobayashi equations with additional gain nonlinearity, the dynamics is limited to external-cavity attractors that develop from the external-cavity modes which have a positive but not too large frequency shift with respect to the solitary laser emission frequency ${\omega }_0.$ Although relaxation oscillations about these external-cavity modes are the first to become undamped as the feedback intensity increases, the attractors that arise from these modes remain stable over the largest range of feedback strengths. Stronger feedback destabilizes the individual attractors, creating new solutions which form from their ruins. At the beginning of the merging, the attractor ruins are not equally visited; the most visited ruins are those of the attractors last destabilized. We explore and explain these results by examining the dynamics of the laser when operating on a single external-cavity attractor.