Attenuation of cutoff modes and leaky modes of dielectric slab structures

A simple formula is developed for the attenuation constant of higher order cutoff modes of a dielectric slab guide and of the modes of leaky guides. The formula is based on a perturbation analysis that reduces the problem to that of the transmission characteristic of a Fabry-Perot resonator. Under certain approximations, the formula for leaky guides reduces to that of Hall and Yeh, but the formula has a wider range of applicability.