Ray-optical solution for the dyadic Green´s function in a rectangular cavity

The ray-optical method, which has been successfully employed for the analysis of diffraction and scattering problems, is used to derive the Green´s function in a rectangular cavity. Despite the asymptotic approximations inherent in the method, it is shown that it gives a physical or geometrical insight into the mechanisms of propagation in guiding structures leading to exact or rigorous solutions not always provided by other methods.