OPTICAL NONLINEARITY STUDIED VIA ANISOTROPIC MICROSTRUCTURE - A NUMERICAL STUDY ON RANDOM IMPEDANCE NETWORKS

Optical nonlinearity is sensitive to the microstructure of materials. When metal clusters are structured on the nanometre scale, they exhibi t a strong nonlinear optical response through the local-field and geom etric-resonance effects. In this work, we analyse a model of anisotrop ic microstructure and examine the effect on the optical nonlinearity i n the quasi-static limit. To model anisotropic microstructures, a comp osite medium is conveniently represented by a random impedance network which consists of both metallic and dielectric bonds. For these netwo rks, we performed numerical simulations in which the metallic bonds ar e assumed to obey the Drude free-electron model. The results show that the absorption peak can be separated from the nonlinearity enhancemen t peak, and hence that an even larger optical nonlinearity can be achi eved than that reported in the literature.