高斯脉冲光场下的三阶非线性极化率的研究

Study on Third-order Nonlinear Polarizability under Gaussian Pulsed Light Field

在三能级原子系统中从理论上建立三阶非线性光学极化率的微扰模型。利用逐级迭代方法求解密度矩阵元的运动方程,求得三能级系统三阶非线性光学极化率公式。在光场为高斯脉冲的情况下,研究了级联跃迁过程的非线性极化率与光场振幅,脉冲宽度之间的关系,三阶极化率反比于激光频谱宽度的三次方。激光频谱宽度越小,越有利于三阶极化率的产生,对于频率而言,能量更加集中。

A perturbation model of third-order nonlinear optical polarizability is theoretically established in a three-level atomic system.The stepwise iterative method is used to solve the equation of motion of the density matrix element,and the third-order nonlinear optical polarizability formula of the three-level system is obtained.In the case where the light field is Gaussian pulse,the relationship between the nonlinear polarizability and the amplitude of the light field and the pulse width of the cascade transition is studied.The third-order polarizability is inversely proportional to the cube of the width of the laser spectrum.The smaller the laser spectrum width,the better the third-order polarizability is generated,and the energy is more concentrated for the frequency.