Simulation of Composite Optical Properties Close to Percolation Threshold

Abstract

ABSTRACTWe analyze the optical properties of a metal-insulator composite thin film close to the percolation transition pc. Using a mean field approximation, it is possible to predict the existence of an optical threshold at a concentration p* slightly larger than pc. At that concentration defined by the vanishing of the real part of the dielectric constant and which depends of the relaxation time and therefore of the microgeometry, the composite optical absorption is frequency independent up to the near infrared frequencies. This property has been observed in a number of granular and cermet films.We show that this property is quite general and can be obtained by generalizing the percolation scaling laws to a mixture of resistors, inductors and capacitors. The quality factor is shown to be a relevant physical quantity.We report and discuss the results of simulations on real analogic LCR circuits and on computer which confirm and explicit these conclusions.