<title>Analysis of wave propagation in straight and bent sections of channel waveguide by physical optics method</title>

Abstract

Channel waveguides are increasingly used as transmission media, filter and coupler, periodic structures and active components. Very recently integration of channel waveguides with microstructure sensors has been proposed. This new application is especially concerned with the behavior of waveguide bending and deformations as well as it's propagation characteristics in straight sections. A number of numerical methods such as FD-TD2, BPM3 and mode matching have been used for analyzing propagation characteristics and discontinuties of these waveguides. These methods are generally (numerically) slow and require a vast amount of computer resources, and therefore are not suitable for design/optimization purposes. Recently a semi-analytical and insightful method based on physical optics for solving discontinuity problems has been proposed4, In which the ray representation of the propagating modes is combined with the equivalent source formulation for a 2-D dielectric waveguide. Here we extend this approach to a 3-D dielectric channel waveguide. This extension requires (plane wave) ray representation of the modal fields in a 3-D channel waveguide. We develop such representation by using Marcatili's approximate field expressions and dispersion relations for a dielectric channel waveguide. This ray picture is then used to determine the radiation from the bent sections.