中文摘要：

应用数值方法研究了倒Y型四能级系统在单向环形光学谐振腔中的光学双稳态特性,应用密度矩阵理论给出了原子系统的密度矩阵运动方程,研究了自发辐射产生相干对光学双稳态阈值的影响。分析发现当探测场与控制场满足双光子共振条件时,原子捕获在两个下能态系统对探测场透明不能形成双稳态,当探测场与耦合场或耦合场与控制场满足双光子共振条件时,系统仍可以形成双稳态。在稳态条件下,自发辐射诱导相干导致两自发辐射通道干涉相消,上能级的粒子数增加,电磁诱导透明窗变窄,双稳态的域值增加。

英文摘要：

Optical bistability in a four-level inverted Y-type atom system inside an optical ring cavity is investigated numerically. Atomic density matrix equations are derived by the density matrix theory. The effect of the Spontaneously Generated Coherence（ SGC） on threshold of the optical bistability is studied.When the probing field and controlling field are in two-photon resonance,the atoms are trapped on the two lower states,probing field is transparent and there is no bistability in the system. But when the probing field and coupling field or coupling field and controlling field are in two-photon resonance,there is the optical bistability in the system. Under condition of the stable state,SGC can make the interference destructive from two transition channels. Population distribution on the higher levels is enhanced,transparency window becomes narrow,and the threshold of the bistability becomes large.