Excitation localization and nonlinear optical processes in colloidal silver aggregates

We present the results on investigation of the photomodification and optical nonlinearities of colloidal aggregates, which are indicative of the localization of optical excitation in fractal clusters. It is shown experimentally that the enhanced optical nonlinearity of aggregated metal colloids is connected with an enhancement of the local field in resonant domains of large clusters. The enhancement factor of nonlinear absorption in aggregated silver colloids is about 700 as compared with nonaggregated samples.