A semiclassical model of two-level atoms driven by a local field is developed. It is shown that this leads to optical bistability without the presence of an optical cavity. The quantitative and qualitative character of this mirrorless bistability is different from cases considered earlier.
Recent interest has focussed on the subject of mirrorless optical bistability, the simplest system showing bistability theoretically is a system of N ≥ 2 atoms. Microscopic theory is derived from quantum theory by a factorization of binary products of operators. There are strong inter atomic interactions in the bistable regime, it is unlikely that these factorizations are valid. Quantum calculations that avoid factorization imply that bistability does not exist. Hence in the previous bistability conference there was skepticism that bistability could really occur in a mirrorless system with only a few atoms.
A two-photon optical bistability equation is derived for a three-level V-type atom in a cavity. We consider the bistable states of the purely absorptive type and investigate the influence of the phase difference of the two cavity field modes on bistability characteristics due to the nonlinear coupling between atomic transitions and fields. Very different results are found for the three cases of phase difference we considered. The bistability is found to diminish when the two modes are in phase, in contrast to the two-level case. In addition, we also discuss the effect of longitudinal and transverse relaxation times on the bistability and how the bistability operation characteristics of one mode can be controlled by adjusting the other.
Absorptive optical bistability is shown to exist for a single two-level atom inside a resonant optical cavity. Solutions for the quantum-mechanical density operator are obtained numerically for a parameter regime at the interface between the quantum limit, in which quantum-mechanical noise invalidates the semiclassical prediction of bistability, and the classical limit, in which quantum noise is a negligible perturbation on semiclassical results. Bimodal photon number distributions and Q functions are obtained, and two-state transition rates are calculated.>