Optical Bistability And Optical Multistability Of Three-level Atoms System

Optical bistability and optical multistability have been extensively investigated in quantum optics and nonlinear optics. During the research of nonlinear optics in the past twenty years, people have clearly realized that, in the mutual action between optical cavity field and two-level atoms, due to nonlinear response to atoms (Absorption and dispersion character of medium depend on the effect of field intensity), the field intensity outputing from optical cavity displays nonlinear bistability feature, i.e. one input state corresponds to two stable output states. The nonlinear system which consists of two-level atoms and optical cavity provides an experimental example that can test typical optical bistability theory.In recent years, people begin to focus on the research of nonlinear optical feature of three-level systems and four-level atoms systems. Nonlinear optical system consisting of three-level atoms and optical cavity, on the condition of weak field, not only has powerful nonlinear effect, but also increase control factor. Meanwhile, optical bistability threshold value can be changed through the changing of coupling field parameter (strength, frequency, etc.). And the combination of powerful nonlinear optical and controllable feature of cavity output make three-level atoms system have huge applied potentiality in optical communication proceeding.In this paper, we study the coherent control of optical bistability and multistability in the V-type three-level atomic system driven by a coherent field. It is shown that the systeresis loop width of optical bistability can be effectively controlled by the coherent field on the two-photon resonance. As the Rabi frequency of the driving field is increased, the threshold intensity obviously is lowered. For the case of the off two-photon resonance, optical multistability occurs in the present system. The hysteresis loop widths are manipulated simply by varying the Rabi frequency of the coherent field.