双光场作用下里德堡原子的粒子数布居

Population distribution of Rydberg atom under the driven of two laser fields

基于光和物质相互作用的密度矩阵方程理论,模拟研究了双光场作用下阶梯形三能级里德堡原子系统的粒子数布居和吸收特性。发现里德堡能级粒子数布居随探测场失谐量的变化与探测吸收一致。当探测场强度小于耦合场强度时,与耦合吸收关联的两能级粒子数布居随探测场强度增加而减小,而与探测吸收关联的里德堡能级粒子数布居增大。探测场、耦合场强度相等时,与探测吸收关联的上下能级粒子数布居相等。之后,继续增大探测场强度,会出现上下能级的粒子数反转,把该现象归因于探测场引起的功率展宽,使受激粒子寿命缩短,中间激发能级的粒子部分吸收探测光子跃迁到里德堡能级,部分快速弛豫到基态能级。所以,对该原子系统,适当选取耦合、探测场强度,可实现受激辐射的放大。

Based on the theory of density matrix equation for the interaction of light and matter,the characteristics of the population and absorption of a ladder type three-level Rydberg atom system under the driven of two laser fields are investigated.It is found that the variation of the population of Rydberg energy level with detuning of the probe field is exactly the same as that of the probe absorption.If the intensity of the probe field is less than that of the coupling one,the population of the two levels which associated with the coupling field decreases with the increase of the intensity of the probe field,but the one of the Rydberg level which associated with the probe absorption increases until to equals the population of the intermediate level.Just then,the intensity of the probe and the coupling field is equal.Then,if the intensity of the probe field continues to increase,population inversion between the Rydberg and intermediate energy level will appear.This phenomena can be attributed to power broadening caused by the probe field.Some atoms of the intermediate excited level are pumped to the Rydberg one,and some atoms relax to the ground level quickly.Thus,by adjusting the intensity of the probe and the coupling field,stimulated radiation can be realized with this Rydberg atomic system.