Abstract

We analyze fluctuation effects of a squeezed electromagnetic reservoir (also termed squeezed vacuum, or SV) on the phenomenon of intrinsic optical bistability (IOB) in a dense collection of two-level atoms. A quantum statistical treatment is developed in the limit of a bad cavity and large dephasing in the medium. Under these conditions we obtain a single operator Langevin equation for the atomic inversion by adiabatic elimination of the atomic polarization variables. By using Ito calculus, the corresponding Fokker-Planck equation is derived, the stationary solution of which yields the probability distribution function for the bistable system as a function of the inversion. In a narrow region of transition, the probability distribution is double peaked with the two peaks corresponding to two metastable states in IOB. Quantum fluctuations can induce the system to jump randomly from one metastable state to the other with certain characteristic (passage) times. Squeezed quantum noise (as in the SV) is found to result in drastic alteration of the intrinsic bistable behavior of the system. Interestingly, the probability distribution and the passage times now exhibit critical dependence on the relative phase between the external driving field and the squeezed vacuum.

© 1992 Optical Society of America