Analysis of the radiative corrections and dynamic extensions to the local field in the effective refractive index of particle suspensions

Abstract

We analyze the predictions of two recently developed effective-medium approximations for the effective refractive index of a system of either transparent or plasmonic spherical particles, dispersed randomly in a transparent liquid matrix, as a function of their geometrical and physical parameters. The importance and significance of these approximations is that besides the radiative corrections to the optical response of the particles, they include full dynamic corrections to the field exciting any given particle. We perform this analysis by comparing the values obtained using them with the ones obtained from three well-known and widely used effective-medium approximations: Maxwell Garnett, Maxwell Garnett-Mie and van de Hulst. We provide plots of the real and imaginary parts of the effective index of refraction, for the five approximations considered, for polystyrene and gold nanoparticles of different sizes, as a function of the filling fraction and wavelength, pointing out the relevance of the new predictions, as well as the actual physical processes behind the so-called dependent scattering and what we now call dependent absorption.