Quantum fluctuations of light at the output of a cavity with absorptive bistability for arbitrary input-photon statistics

The general expression of the output-light Mandel parameter xi(out) is obtained in case of purely absorptive bistability, for arbitrary value of xi(in) of incident light (the xi - parameter measures the deviation of the photon-flow statistics from Poisson statistics). Calculations are based on stochastic rate equations. No adiabatic elimination of atomic variables is made; the coherent nature of "incoming" of incident photons into a cavity is correctly taken into account. On condition of bistability, although the strongly sub-Poisson input-photon statistics (xi(in) = -1) generally reduces the output noise as compared to the case of coherent input (xi(in) = 0), the inequality xi(out) > 0 still holds near the switching points.