Optical properties of random heterogeneous composite materials: from binary to ternary compounds

Abstract

We report an experimental study on the optical properties in the visible and near infrared of three-dimensional random composite materials, made of pellets of KBr filled either with Ge or TiO 2 particles (binary composite materials), or with both Ge and TiO 2 particles (ternary composite materials). Hemispherical factors (reflectance and transmittance) of binary and ternary composites have been measured on pellets with various concentrations, in a wavelength range extending between 0.3 and 1.8 μm. The transport of light through the materials has been modelled with a Monte Carlo simulation, used together with the Mie theory. In the case of ternary compounds, we propose two approaches to describe multiple scattering in the samples, which prove to be equivalent in the wavelength and concentration ranges considered. One approach is based on the definition of a unique equivalent scatterer and provide the definition of an effective binary medium (whose characteristics are explicitly given) optically equivalent to the ternary compound.