级联型四能级原子相干介质中的光学双稳态和多稳态

主要研究了在一单向环形腔内的级联型四能级原子被三个光场驱动的光学双稳态和多稳态行为. 三个单模光场通过三个光子跃迁路径与原子系统耦合. 在这种情况下，中间两能级间所加的耦合场Ω_B变得非常重要. 研究显示耦合场Ω_B的增加会使光学双稳态的阈值减小,同时也会导致光学多稳态的产生.对上面两能级间所加的耦合场的作用也进行了讨论,同时还讨论了探测场失谐和合作参数对光学双稳态及多稳态的影响. 关键词： 原子相干 光学双稳态和多稳态 四能级原子

Optical bistability and multistability in ladder-type four-level atomic coherence medium

Optical bistability（OB） and optical multistability（OM） behaviour of ladder-type four-level atom in a unidirectional ring cavity driven by three laser fields is studied. Three paths of photon transition are coupled with the laser fields. In this case, the laser field Ω_B coupling with two middle levels is very important. When the Ω_B is increased, optical bistability threshold significantly decreases and optical multistability appears. The effects of the laser field coupling with two upper levels on optical bistability are also discussed. Furthermore, we analyze the effects of the detuning of probe field and atomic cooperation parameter on OB and OM.