A numerical investigation of effective optical characteristics of dielectric mixture layer on Si sphere by FDTD method

Abstract

This paper reports on a numerical simulation of the optical characteristics of a dielectric mixture layer formed on a Si substrate using the finite-difference time-domain (FDTD) method. This study investigated the validity of using effective medium approximation (EMA) layers in thin mixture film problems with the optical constants of bulk materials. The complex reflection coefficients of Si substrates with randomly distributed thin mixture films fabricated from water/SiO2 and water/carbonaceous materials were numerically evaluated at normal and oblique incidences of plane electromagnetic waves via the FDTD principle, and the possible effects of the mixture layers on the effective optical characteristics were investigated. We observed that Bruggeman’s model based on EMA provides a good prediction of the behaviour of the plane wave reflected by the Si surface with randomly distributed mixture layers. The results also suggested that mixture layers have effects under oblique incidence, but they have no significant impact under normal incidence.