Abstract

We investigate the effect of geometric anisotropy on optical nonlinearity enhancement for composites with semiconductor elliptical cylinders in an insulating host in a square lattice. The frequency dependences of the effective nonlinear susceptibility are calculated, and the optical nonlinearity of the composites near the percolation threshold are studied. The calculations are based on the Stroud–Hui relation and a series expression of the space-dependent electric field in periodic composites. The results show that, analogous to metal–insulator composites, a local minimum appears in the nonlinear optical responses near the percolation threshold for two-dimensional percolating semiconductor–insulator composites with geometric anisotropy when the ratio of the bound-electron number density to the effective mass of the electron is large. The results also show that the nonlinearity enhancement increases almost to its maximum when a structure with layers of fluctuating thicknesses forms, and there are no further obvious increases of the enhancement when the thickness fluctuation of the layers decreases. We compare the results of our calculation with those calculated by use of the Boyd–Sipe relation in layered composites, and we conclude that the nonlinearity enhancement reaches its maximum when composites with elliptic cylinders are transformed into Boyd–Sipe-type layered composites.

© 2002 Optical Society of America