NOISE-INDUCED SWITCHING AND STOCHASTIC RESONANCE IN OPTICALLY NONLINEAR CDS CRYSTALS

We investigate the influence of noise present in the periodic input si gnal of a passive optically bistable element. The thermally induced ab sorption nonlinearity of CdS crystals is used to achieve optically bis table behavior. By measuring the signal-to-noise ratio (S/N) of the no isy modulated input signal and of the output signal the phenomenon of stochastic resonance is found: With increasing noise strength the S/N increases up to a maximum value corresponding to the above resonance a nd then decreases again. The S/N of a noisy input can be enhanced by u p to approximately 6 dB with this system. Furthermore, the cases of si nusoidal and rectangular modulation of the bistable element are compar ed.