Ray-optics analysis of inhomogeneous biaxially anisotropic media

Firm evidence of the biaxial nematic phase in liquid crystals, not induced by a magnetic or electric field, has been established only recently. The discovery of these biaxially anisotropic liquid crystals has opened up new areas of both fundamental and applied research. The advances in biaxial liquid-crystal-related topics call for a good overview on the propagation of waves through biaxially anisotropic media. Although the literature sporadically discusses biaxial interfaces, the propagation of waves through inhomogeneous biaxially anisotropic bulk materials has never been fully addressed. For this reason, we present a novel ray-tracing method for inhomogeneous biaxially anisotropic media. In the geometrical-optics approach, we clearly show how to assess the optical properties of inhomogeneous biaxially anisotropic media in three dimensions.