Test of gyrotropic constitutive relations by specular light reflection

Abstract

Gyrotropic media are generally characterized by skew symmetric (electric) permittivity and (magnetic) permeability tensors. There is wide belief, however, as expressed In both expository and research literature, that only the permittivity takes a tensorial form for intrinsically nonmagnetic materials whose electrooptic behavior is of interest. I show that neglect or inclusion of light-induced magnetic anisotropy leads to qualitatively different physical predictions (even in the simplest case of an isotropic optically active medium) for gyrotropic effects manifested in specular reflection from the surface of the medium rather than in light propagation through the interior of the medium. In particular, differential reflection of circularly polarized light differs markedly as a function of incident angle, reaching peak value either beyond Brewster angle or near normal incidence, depending on whether a tensorial or scalar expression, respectively, relates vectors H and B. A scalar relation also leads to internal inconsistencies such as slight violations of energy conservation. The differences in constitutive relations are most significant on implementation of electromagnetic boundary conditions. This accounts for why light-induced magnetic anisotropy Influences differential light reflection but not optical rotation or circular dichroism.