FORBIDDEN DIRECTIONS FOR TM WAVES IN ANISOTROPIC CONDUCTING MEDIA

We investigate the wave propagation properties of nonuniform plane wav es in an (unbounded homogeneous) anisotropic conducting material, Such waves (for which amplitudes vary across surfaces of constant phase) c haracterize the refracted field in an imperfect dielectric, like the e arth when a uniform electromagnetic plane wave is incident from the ai r, The results, presented in terms of polar diagrams of the attenuatio n, slowness, energy velocity, and quality factor predict the existence of ''stopbands'' beyond a given degree of nonuniformity (i.e., combin ations of propagation and attenuation directions where there is no wav e propagation). This is a peculiar effect due to the joint presence of anisotropy and conductivity that may have application in the design o f synthetic materials acting as absorbers of electromagnetic radiation .