Experimental evidence of van der Pol-Fitzhugh-Nagumo dynamics in semiconductor optical amplifiers

Thermo-optical pulsing in semiconductor amplifiers is experimentally shown to correspond to a very com-mon excitable scenario ~the van der Pol Fitzhugh Nagumo system!. Self-sustained oscillations appear in the sequence predicted by this simple dynamical model as we change either the injection level or the bias current. Periodic modulation of these parameters leads to the characteristic phase-locking structure. Furthermore, co-herence resonance is observed when external noise is added to the system.