若干有机分子的二阶非线性光学极化系数色散关系

在INDO/CI方法基础上, 用自己编制的计算二阶非线性极化系数β_(ijk)程序, 计算了苯胺、硝基苯、对硝基苯胺和4-硝基-4′-胺基二苯乙烯的β_(ijk), 并研究了其对外部激光场频率的依赖关系。结果表明, 分子内的电荷转移是产生非线性光学现象的根本原因, 而作为外因的激光场对二阶非线性光学系数的大小和方向也有直接的重要作用。当激光场频率与分子的共振频率接近时, 二阶非线性极化系数变得非常大, 在共振频率附近, β_(ijk)改变符号且Kleinman对称性被打破。

THE DISPERSIONS OF THE SECOND-ORDER NONLINEAR SUSCEPTIBILITIES OF SOME ORGANIC MOLECULES

At the level of INDO/CI methods, using the program for calculations of the second-order nonlinear susceptibilites (β_(ijk)) written by ourselves, we calculated the β_(ijk) of aniline, nitrobenzene, ρ-nitroaniline and 4-nitro-4′-aminostilbene and inves-tigated dependence of β_(ijk) on LASER frequencies. It is shown that the intramolecular charge transfer is the origin of the nonlinear optics phenomenon and the LASER field plays an important role to the magnitude and direction of the second-order nonlinear optics susceptibility. When the LASER frequency is close to the molecular resonance frequency, the second-order nonlinear susceptibility becomes larger, before and after the resonance freguence, β_(ijk) changes its sign and the Kleinman symmetry begins to break down.