Waveguide mode propagation in optical waveguides containing uniaxial media is investigated. When the optical axis of each uniaxial medium lies in the plane containing the waveguide normal and the propagation direction, waveguide propagation is described by uncoupled TE and TM modes. The phenomenon of wave-front tilt is discussed and exact mode dispersion equations are derived. The experimentally convenient situation of the optic axis lying in the film plane is also analyzed. Here mode coupling between TE and TM polarizations occurs and the propagating modes are hybrid. The wave-vector components in the uniaxial media transverse to the waveguide are shown to have ordinary or extraordinary characteristics. Exact mode-dispersion equations for the hybrid modes are derived and are shown to differ substantially from the TE and TM mode approximations when the latter are near degeneracy.
W. K. Burns and J. Warner, "Mode dispersion in uniaxial optical waveguides," J. Opt. Soc. Am. 64, 441-446 (1974)