具有分形结构掺入物的二维复合材料三阶光学非线性性质的计算

利用傅里叶展开和退耦合近似方法， 在二维金属-绝缘体复合材料中， 当金属掺入物形成具有分形结构的聚集物集团时， 计算其三阶光学非线性电极化率χ_{e与外电场频率ω的关系. 结果表明， 在一些特定的频率值， Re(χe)-ω曲线出现了显著的放大峰. 与以正方点阵规则排列的柱型掺入物的情 况相比， 掺入物形成具有分形结构的聚集物集团时， 原有放大峰的强度明显减弱， 但有新的放大峰出现， 其峰强非常敏感地依赖于金属材料的特征驰豫时间τ.}

Calculation of Third Order Optical Nonlinear Susceptibility of Two-dimensional Composites with Fractal Geometry

By means of the Fourier expansion technique and the decoupling approximation, the frequency dependence of the third order optical nonlinear susceptibility χ_e of composites with fractal geometry was ca lculated. The results show that obvious enhancement peaks occur in the Re(χ_{e)-ω curves at particular frequencies. Compared with the composites in which the inclusions were arranged in a periodic square lattice, when the fractal clusters of the inclusions were formed, the enhancement peak occurred in the case of periodic lattice was weakened, and new enhancement peaks occurred. The results also show that the intensities of the enhancement peaks were sensitively dependent on the characteristic relaxation time τ.}