Angular dependence of the reflectance from an isotropic polydomain medium: experimental verification

Abstract

Based on average reflectance and transmittance theory (ARTT) it has been shown recently that randomly oriented polydomain materials with optically large domains can exhibit an unusual behaviour of the dependence of reflectance on the angle of incidence. In contrast to isotropic polydomain media with optically small domains it was found, for example, that Rp can exceed Rs at certain angle of incidences ranges if the domains are optically uniaxial. This theoretically predicted behaviour has been proved by experimental spectra of randomly oriented polycrystalline fresnoite recorded at an angle of incidence of 70° at the high-wavenumber side of the reststrahlen region. While the correspondence between simulated Rp and Rs spectra based on the single-crystal data and the experimental spectra is quite acceptable, it was necessary to refine these single-crystal data in order to obtain a satisfactory resemblance between the simulated and experimental cross-polarization terms.