Vibrational resonance in a noisy bistable system: nonfeedback control of stochastic resonance

We present theoretical and experimental results on the effect of additive noise on vibrational resonance (VR), occurring in a bistable system excited by two periodic forces with very different frequencies. In the noiseless case, the phenomenon shows up as a parametric amplification of the low-frequency (LF) signal near the onset of bistability controlled by the additional high-frequency modulation. The presence of noise leads to the diminution of the gain factor (G) and signal-to-noise ratio (SNR) for the LF signal which obey scaling laws depending on the noise intensity. At the same time both G and SNR are always higher than the ones which could be obtained in the same conditions through the use of stochastic resonance (SR). As a consequence, VR can be used for the effective nonfeedback control of SR in noisy bistable systems. The experimental results obtained in a bistable vertical cavity surface emitting laser are compared with the theory showing a good agreement.