Influence of surface polaritons on mode attenuation in a middle-infrared irregular dielectric cavity waveguide

Geometric-optics methods supplemented by phenomenological results on wave reflection from a randomly rough surface of a dielectric, for which the real part of the permittivity function is negative and the imaginary part is small, are used to study the influence of the excitation of surface polaritons induced by roughness of the walls of a cavity waveguide channel on the propagation constants of the modes in this waveguide. It is found that the coupling of the waveguide mode field to surface polaritons as a result of the random irregularity of the walls of the guiding channel is responsible for a considerable increase in the mode attenuation in the waveguide.