AN APPROACH TO RAY OPTICS IN ANISOTROPIC MEDIA

A description of the far fields radiated by an electromagnetic point source in the presence of bounded, lossless, anisotropic media is formulated in terms of ray optics. The ray-optical description is a generalization of classical geometrical optics and has previously been used to describe the fields radiated in isotropic media and those radiated by line sources in anisotropic media. In formulating the ray-optical description, the fields radiated by a point source in the presence of a planar interface between two homogeneous, lossless media of arbitrary anisotropy are first presented in terms of a double Fourier integral. This rigorous integral representation is then evaluated asympototically to find the first-order stationary point, branch curve and surface wave pole contributions. Using the equality of group velocity and velocity of energy transport for plane waves in anisotropic media, the stationary point contributions are interpreted in terms of direct and scattered transmitted and reflected rays and the associated fields are cast into ray- optical form. Locally, the direct and scattered ray fields are those of plane waves carrying energy in the ray direction and are scattered at the interface according to Sneels law. The ray-optical forms of these ray fields exhibit their dependence on properties local to the ray path, thus permitting the extension of the ray-optical results to problems not amenable to rigorous analysis.