DETAILED STUDY OF QUASI-BOUND MODES IN LEAKY STRUCTURES

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 l eaky waveguides with delta function barriers for which a simple analyt ical characteristic equation is available. The method is applied for t he determination of eigenvalues of prism-loaded multilayer waveguides. The influence of the prism coupler on the waveguide modes is investig ated in detail for slab and four-layer waveguides. The method is compa red with several approximate methods.