Coherent Control Of Optical Bistability And Multistability In A Two-level Atomic System

In recent years, the phenomenon of optical bistability and multistability, which is an important subject in the fields of quantum optics and nonlinear optics, has been paid a great deal of attention. A variety of optical cooperative phenomena have been found. On the other hand, great progress has been made in the coherent effects such as electromagnetically induced transparency, enhanced index of refraction and enhancing nonlinear optics processing, and so on. In this paper we focus on the coherent control of the optical bistability and multistability.We consider an ensemble of two-level atoms confined in a unidirectional optical ring cavity. By employing the harmonic expansion and matrix inversion, we calculate the polarization of the medium and analyze the interference effect of the coherent field is investigated. It is shown that the cooperative behavior is strongly dependent on the Rabi frequency of the coherent driving field. When the driving field Rabi frequency is varied, switching from the optical bistability to the optical multistability occurs. The hysteresis loop width of the optical bistability is manipulated simply by varying the Rabi frequency.