Abstract

Dielectric slab waveguides are needed in the construction of essentially all integrated optics devices. In practical integrated optical circuits, the direction of propagation must change over the substrate and thus it is essential to understand the allowed modes that can propagate for a particular direction. Rigorous electromagnetic theory is applied to determine the allowed modes (both sustained modes and leaky modes) in a uniaxial crystalline waveguide such as lithium niobate. For an arbitrary direction of propagation, the directions of power flow and phase propagation differ. The sustained modes in this case may be classified as TE-like modes and TM-like modes with coupling occurring between them. For the same waveguide parameters, it is shown that a simple change of propagation direction can cause multiple allowed modes to become cut off. The conditions for cutoff are discussed. Integrated optical polarizing devices based on anisotropic cover layers are discussed.

© 1985 Optical Society of America