Localized states and excitability in a monolithic VCSEL with saturable absorber

We present experimental results on nonlinear localization and excitability in an original design of a Vertical Cavity Surface Emitting Laser with intracavity saturable absorber. Depending on the sample temperature, the VCSEL with saturable absorber can be locally bistable or self-pulsing at threshold. In the first case, self-localized states (laser cavity solitons) are demonstrated, excited and erased incoherently at a fast rate. We present also evidence of optical manipulation of self-pulsing states. In the second case, type III excitability is demonstrated. Excitability in a laser with saturable absorber occurs below the self-pulsing instability domain and is characterized by : 1) a threshold in the response to an input perturbation leading to a “all or nothing” type of response and 2) the appearance of a calibrated response above threshold. We compare our experimental results to a model, including the effect of noise. Finally, we present numerical results on an array of coupled micropillar cavities demonstrating nonlinear wave propagation. The vertical cavity design presented here could constitute a compact platform for realization of various micro and nanophotonic semiconductor devices for applications to innovative all-optical signal-processing tasks, e.g. excitable logic-gates or reservoir computing.