Anomalous absorption of bulk electromagnetic waves by an ultra-thin layer

A strong maximum of absorption (as much as 100%) of bulk TE electromagnetic waves by an ultra-thin film with large imaginary dielectric permittivity between two semi-infinite media is shown to exist at an optimal film thickness. This optimal thickness is demonstrated to be usually much smaller than the wavelength and the wave penetration depth in the film. A 100% absorption of TE electromagnetic waves is shown to occur in the middle infrared range in an extremely thin film of an ionic crystal of several tens of nanometers, or just several nanometers. Physical reasons for this anomalous absorption are discussed. Frictional contact approximation, in which the layer can be considered as an immediate contact between two half spaces with special boundary conditions, is introduced and justified. Similarity of these boundary conditions with mechanical boundary conditions at a contact with Liquid friction is investigated. The anomalous absorption of electromagnetic waves in thin non-uniform layers with the dielectric permittivity varying across the layer is analysed in the frictional contact approximation. Significant differences in the anomalous absorption of TE and TM waves are pointed out and investigated. (C) 1998 Elsevier Science B.V. All rights reserved.