ON THE VARIATIONAL REACTION THEORY FOR DIELECTRIC WAVEGUIDES.

Using the reaction concept, a variational theory is established for treating the scattering and propagation problem associated with a dielectric waveguide which is illuminated by an obliquely incident plane wave. The theory properly absorbs radiation and continuity conditions into the variational equation. This equation is then solved by the finite-element method together with the frontal solution technique. The propagation constants of the guide are obtained by searching for the poles of the scattering coefficients when an inhomogeneous wave is incident. Two attractive features of this approach are the avoidance of spurious modes and the accuracy of the results even for the modes near cutoff. Although the proposed theory may be applied to dielectric waveguides of arbitrary cross section, only the rectangular waveguide is investigated in detail. Also included are numerical results for the propagation constants when in refraction indices, aspect ratios, and index profiles are varied. 22 refs.