Dynamics and stochastic phenomena in an excitable laser with long delayed feedback

A comprehensive investigation of the excitable behavior of a semiconductor laser with long delayed feedback is reported. Starting with the characterization of the solitary laser, we show how the addition of long-delay feedback produces a dynamics similar to spatio-temporal excitable systems, with propagation and noise-induced creation and destruction of excitable pulses in the pseudo time. A phenomenological model well describes the system and allows for a comparison of the observed regimes with the measurements. The addition of a variable quantity of noise leads to the occurrence of a phenomenon that we term "transient coherence resonance" evidenced in the experiment and in the numerical model. A simple stochastic process is also introduced and allows us to explain the features observed in terms of the key dynamical ingredients of the physical systems.