循环四能级相干原子介质中的光增益

我们在一个循环四能级相干原子系统中,理论研究了抽运场与调制场强度对信号场增益的作用。研究表明,在循环四能级相干原子介质中,调制场改变了四个能级间的粒子数布居分布,导致信号场被增益放大。对于N型四能级原子系统,当加入微小的调制场(调制场强度与信号场相等)时,共振处信号增益峰值提高了12倍。相干抽运场诱导信号场放大,且改变抽运场强度可以实现信号场由对应粒子数反转增益到无粒子数反转增益。且随着抽运场强度增加,共振增益的取值先变大后变小。该循环系统在光放大及增益效应研究中可能有重要应用。

Optical Gain in a Closed-loop Four-level Coherent Atomic Medium

In a closed four-level coherent atomic system,we theoretically studied the effect of pump field and regulated field intensity on signal gain.Studies have shown that in a circulating four-level coherent atomic medium,the regulated field changes the distribution of population among the four energy levels,causing the signal field gain to be amplified.When added the regulated field(the intensity of regulated field is equal to that of the signal field),the signal gain is improved 12 times in contrast with N-type four-level system.Coherent pump field induces signal field amplification,and changing the pump field intensity can achieve signal field from the corresponding population number inversion gain to no population inversion gain.As the intensity of the pump field increases,the value of signal gain grows and then reduces.The closed-loop system may have important applications in optical amplification and gain effect.