用四能级系统研究相干布居囚禁态  

Study of Coherent Population Trapping State with a Four-Level System

作　　者：李强[1,2] 云恩学[1,2] 顾思洪[1] 

机构地区：[1]中国科学院武汉物理与数学研究所,湖北武汉430071 [2]中国科学院研究生院,北京100039

出　　处：《中国激光》2009年第2期351-355,共5页Chinese Journal of Lasers

基　　金：国家自然科学基金(10574141;1067516)资助项目

摘　　要：为了了解双色激光对相干布居囚禁(CPT)原子频标和CPT磁场计等设备制备CPT态的特性,开展了用双色相干光对充有缓冲气体的样品泡中热运动^(87)Rb原子制备CPT态的研究。将所有与激光无直接作用的态归结为一个"leaky trap"能态,用一个简化的四能级系统数学模型通过求解光学布洛赫(Bloch)方程对制备CPT态的特性开展了理论研究,重点讨论了热碰撞对于制备CPT态的原子能态的A构型中两基态的消相干效应。研究结果表明,热碰撞程度决定系综制备出CPT态的比例,这一消相干机制还造成系综的最大相干度偏离双色光两光强相等处。给出一个简化表达式,用来粗略估计CPT频标和CPT磁场计中消相干碰撞以及激光光强对相干程度的影响。In order to investigate the characteristics of dichromatic laser in preparing coherence population trapping （CPT） states in CPT atomic clock and CPT magnetometer, thermal 87Rb atoms are sealed with buffer gas in a glass bulb are prepared into CPT states with dichromatic coherent radiation field. We attribute all states without direct interaction with bi chromatic coherent radiation field as a ＂leaky trap state＂, and describe the system with a simple four-level system. Through solving optical Bloch equations of the four-level system, we have theoretically studied the preparation of CPT states, especially the de-coherent effects by thermal collision on the two ground states of the A structure. The results reveal that this de-coherent collision not only decides the rate of prepared CPT states, but also causes the maximal coherence deviating from the equal intensities of bi chromatic components. A simple expression is given for roughly estimating the influences of de-coherent collision and laser intensity.

关 键 词：激光光谱 相干布居囚禁 光学布洛赫方程 原子热碰撞 双色激光场 

分 类 号：O433.54[机械工程—光学工程]