Angular dependence of the reflectance from an isotropic polydomain medium: the influence of absorption

The angular dependence of the reflectance from an absorbing randomly oriented polydomain medium consisting of domains either small or large compared with the wavelength is investigated. Besides the two conventional cases, where the refractive index of the incidence medium is either smaller or larger than the averaged index of refraction (small-domain limit) or every principal index of refraction of the domains (large-domain limit), we also discuss a third principal case, which exists only in the large-domain limit. In this third case, only one of the principal indices of refraction is larger than that of the incidence medium, while the averaged index of refraction is smaller. Thus, in contrast to the small-domain limit, total reflection is completely suppressed even in the absence of absorption. A characteristic property of such a polydomain medium is its ability to considerably depolarize linear polarized light in spite of being optically isotropic. Additionally, the parallel polarized reflectance Rp can exceed the perpendicular polarized reflectance Rs over certain angle of incidence ranges. Absorption decreases these domain-size-dependent properties, even under the assumption of constant anisotropy. Nevertheless, for materials with low absorption indices, these effects can affect the optical properties significantly.