中文摘要：

Bistability behaviors in an optical ring cavity filled with a dense V-type four-level atomic medium are theoretically investigated.It is found that the optical bistability can appear in the negative refraction frequency band,while both the bistability and multi-stability can occur in the positive refraction frequency bands.Therefore,optical bistability can be realized from conventional material to negative index material due to quantum coherence in our scheme.

英文摘要：

Bistability behaviors in an optical ring cavity filled with a dense V-type four-level atomic medium are theoretically investigated. It is found that the optical bistability can appear in the negative refraction frequency band, while both the bistability and multi-stability can occur in the positive refraction frequency bands. Therefore, optical bistability can be realized from conventional material to negative index material due to quantum coherence in our scheme.