五能级双梯形原子系统的克尔非线性解析模型

An analytical model for Kerr nonlinerarity in a five-level double-ladder atomic system

摘要:

多能级原子系统是获得克尔非线性的一种可操控光学介质，本文旨在对87Rb原子五能级双梯形结构中的克尔非线性进行理论研究。利用半经典的密度矩阵方程组迭代微扰方法，分别导出了静态原子和热运动原子的线性极化率及非线性极化率的解析表达式。研究表明，这种五能级原子介质在四个光场量子相干作用下表现出多重电磁感应透明性（EIT），克尔非线性总是与吸收光谱反向相关，在每个EIT区域都出现一对克尔非线性系数的正负峰值。还阐明了多普勒效应对吸收谱的增宽作用和色散斜率的压窄作用。该解析模型可以方便地拟合实验数据，并应用于光子器件。

Abstract:

A multi-level atomic system is a controllable optical medium for obtaining Kerr nonlinearity. This paper aims at theoretical research on Kerr nonlinearity in five-level double-ladder 87Rb atomic system. Using the semi-classical density matrix formulation along with an iterative perturbation technique, analytical expressions of the linear and nonlinear susceptibilities are derived for stationary as well as for moving atoms. Research has shown that, this five-level atomic medium exhibits multiple electromagnetic induced transparency (EIT) at four fields with quantum coherent .,at the same time, the Kerr nonlinearity is always inversely correlated with the absorption spectrum, and a pair of positive-negative peaks of Kerr nonlinearity coefficients appear in each EIT region. It also elucidated the broadening effect of the Doppler effect on the absorption spectrum and the narrowing effect on the dispersion slope. This analytical model can easily fit experimental data and be applied to photonic devices.