Amplification of near-resonant signals via stochastic resonance in a chaotic CO2 laser

We show experimentally and numerically that a chaotic CO2 laser with modula ted losses operating in the region of an intermittency resulting from the h and-merging crisis can serve as an amplifier of near-resonant signals, i.e. , signals with a frequency close to the first subharmonic frequency, via de terministic stochastic resonance. The mechanism underlying stochastic reson ance in this case is a synchronization of the random switching events betwe en two chaotic repellers after the band-merging crisis with near-resonant s ignals at the detuning frequency. We demonstrate experimentally that the ga in factor in chaos is larger than near the first period-doubling bifurcatio n by a factor of 2. Numerical results obtained in a two-level rate-equation model are in good agreement with the experimental ones.