Application of infra-red surface electromagnetic waves on metals in nondestructive surface testing

The elementary theory of surface electromagnetic waves (SEW), based on a local relation between the induced current density and electric field, is discussed. Based on this theory, typical values of propagation lengths and penetration depths are calculated in the infra-red and visible regions. Experiments using a double-prism configuration have been performed to demonstrate the relative coupling efficiency as a function of prism-gap height and angle of incidence, respectively, for infra-red SEWs. Approximate calculations of propagation lengths for infra-red SEWs on rough surfaces are presented.