Modal fields of anisotropic channel waveguides

Abstract

We present an approximate analysis of the model fields and dispersion relations of anisotropic dielectric waveguides of rectangular cross section. We initially assume that the dielectric tensor is diagonal in both the guiding and substrate regions of the channel, with a step discontinuity at their interface. Off-diagonal elements in the dielectric tensor are then accomodated by means of coupled mode theory; continuous transverse variation of the dielectric tensor is taken into account by adapting a heuristic technique due to Miller. We have found that the anisotropy may act to decouple orthogonally polarized components of the field, resulting in almost-linearly-polarized modes for many cases of practical interest. We have also considered the coupling of energy between two such channel waveguides running parallel to one another.