Detailed Study of Quasi-bound Modes in Leaky Structures

Abstract

The inconsistency of the progressive wave boundary conditions for the quasi-bound modes in open leaky structures is shown and a new boundary value formulation is developed. The results obtained are tested for leaky waveguides with delta function barriers for which a simple analytical characteristic equation is available. The method is applied for the determination of eigenvalues of prism-loaded multilayer waveguides. The influence of the prism coupler on the waveguide modes is investigated in detail for slab and four-layer waveguides. The method is compared with several approximate methods.