Experimental evidence of coherence resonance in an optical system

Experimental evidence of coherence resonance in an optical system is report ed. We shaw that the regularity of the excitable pulses in the intensity of a laser diode with optical feedback increases when adding noise, up to an optimal value of the noise strength. Both phase and amplitude fluctuations of the pulses play a relevant role in the dynamics of the system. We introd uce the joint entropy of the two variables to generalize the indicator of c oherence, and we put in evidence the mechanism of destruction of the excita ble orbit after the resonance.