Chaotic transitions and low-frequency fluctuations in semiconductor lasers with optical feedback

This paper examines the dynamical origin of low-frequency fluctuations (LFFs) in semiconductor lasers subject to time-delayed optical feedback. In particular, we study chaotic transitions leading to the onset of LFFs by numerical integration of Lang–Kobayashi equations for a laser pumped near threshold. We construct a bifurcation analysis scheme that enables the classification of the different operation regimes of the laser. We use the scheme to study the coexistence of the LFFs and stable emission on the maximum gain mode (MGM), which was the subject of recent experiments [T. Heil, I. Fischer, W. Elsäßer, Phys. Rev. A 60 (1999) 634]. Our computations suggest that as the feedback level increases, the regime of sustained LFFs alternates with regions of transient LFFs, where the laser can achieve stabilization on the MGM. Exploration of the parameter space reveals strong dependence of the structure of the LFF dynamics and the coexistence regime on the value of the linewidth enhancement factor.