Abstract

Dielectric planar waveguides are important components in integrated-optical devices and circuits. The guiding layer of a waveguide may be naturally biaxial (anisotropic) or may become biaxial via the electrooptic effect,¹ thereby affecting the characteristics of the propagating modes. However, the anisotropic nature of these waveguides is usually ignored, since the analysis required to include anisotropy is much more complex than for the isotropic case. The allowed modes are hybrid, in general, as the corresponding propagation constants are dependent on the orientation of the principal dielectric axes of the biaxial layer with respect to the waveguide/device coordinate system. These constants are calculated electromagnetically without approximations. The electromagnetic fields of these modes consist of the weighted sum or four extraordinarylike plane waves which are coupled. Three types of allowed hybrid mode are identified: homogeneous pure guided inhomogeneous pure guided, and leaky guided. Existing within these mode classes are unconditionally stable modes and critically stable modes. Mode cutoff can occur with a transition from one of the latter two mode types to either a leaky guided mode or leaky unguided wave. The cutoff conditions are quantified numerically.

© 1991 Optical Society of America