The Propagation and Excitation of Surface Waves in an Absorbing Layer - Abstract

Abstract

A theory is developed to study TM-type surface waves propagating along a thin absorbing layer on an infinite perfectly conducting plate. It is assumed that the layer is homogeneous and isotropic. The loss mechanism includes both electric and magnetic losses. A new phenomenon, which indicates the existence of an upper cutoff frequency for surface waves, has been discovered. This phenomenon does not exist in the case of isotropic lossless layers. It was known probably only for magneto-static surface waves on lossless ferrite substrates. The difference is found between surface waves on an absorbing isotropic layer and magneto-static surface waves. It concerns the phase velocity near the upper cutoff frequency. This quantity for surface waves on absorbing isotropic layers tends to the speed of light, while the phase velocity of magneto-static waves tends to zero. All basic characteristics of surface waves on an absorbing layer are analyzed. They include the attenuation factors due to electric and magnetic loss mechanism, spatial orientations of phase and amplitude fronts inside a layer, phase and energy velocities, resonance behavior, and launching efficiency. The latter is calculated for surface waves excited by aperture-limited plane waves. A new value for the product of the energy velocity and phase velocity is found. It is shown that in the case of lossless layers, the energy velocity is equal to half of the phase velocity.