Anomalous absorption of electromagnetic waves in a layered structure with complex permittivities

It is shown theoretically that the absorptivity of bulk TE and TM electromagnetic waves by a thin layer with large complex dielectric permittivity has a strong (as much as 100%) maximum at an optimal layer thickness that is usually much smaller than the wavelength and the wave penetration depth (skin-depth) in the layer. The analysis is carried out in the frictional contact approximation, in which the layer can be replaced by a contact of the surrounding media with special boundary conditions that are analogous to the conditions at a contact with linear mechanical friction. The effects of a non-zero real part of the layer permittivity, and non-zero dissipation in the surrounding media on the anomalous absorption are investigated theoretically in detail. Simple analytical equations for the absorptivity maximum, optimal layer thickness and optimal incidence angles are derived and analysed. Differences in the anomalous absorption of TE and TM waves in layered structures with complex permittivities are described and explained from the physical point of view. (C) 1999 Published by Elsevier Science B.V. All rights reserved.