Optical Response of a Hematite Coating: Ellipsometry Data versus Fourier-Based Computations

Abstract

The optical properties of a hematite-epoxy coating are predicted numerically and compared with ellipsometry measurements. The highly-heterogeneous dispersion of nanocubic hematite particles in the epoxy resin is simulated using a previously developed two-scales random model. The local anisotropic permittivity tensor of hematite particles, and that of the epoxy, are estimated by ellipsometry measurements carried out on a macroscopic hematite and epoxy samples. Fourier-based methods using a "discrete" Green operator are used to treat complex permittivities. They predict the effective and local electric displacement field in the quasi-static approximation. The former is close to two estimates based on the Hashin-Shtrikman bounds and a self-consistent approximation. Good agreement is found between experimental data and FFT computations in the whole range of the visible spectrum.

Predictive rendering of composite materials: a multi-scale approach

“…Our approach is built on recent work by Couka & al. in modeling the multi-scale dispersion of nanoparticles in a hematite coating [15] and its optical response computed by a Fourier-based method [16]. The first step consists of characterizing the 3D structure of the material.…”

“…Nevertheless, in recent works [14] [18], a spectral Fourier-based approach has been proposed for the quasi static approximation. These methods have been compared to optical measurements [16] of the same hematite-epoxy sample. Spectroscopic ellipsometric measurements have been made separately for the epoxy and for the hematite and used with the Fourier-based method to compute the effective permittivity of the hematite-epoxy coating.…”