Dielectric and optical properties close to the percolation threshold. II

Abstract

We present a two-dimensional simulation of the optical properties of granular metal films using the Frank and Lobb algorithm. The results are compared with the effective-medium approximation (EMA). Close to the percolation threshold we obtain excellent agreement between the simulation and the EMA. It is shown that the anomalous absorption in the near ir stems from the broadened spectrum of surface-plasmon (or cluster) modes and the percolation scaling law for a mixture of two conductors. This model is able to account for the absorption, reflection, and transmission of thin semicontinuous gold films and their frequency independence at the optical percolation threshold. The discrepancy between EMA and the simulations and experimental data at the edges of the cluster-mode spectrum and in the Lifshitz tails outside the critical region are due to configuration fluctuations neglected in the EMA.