Asymptotic behaviour of a subwavelength nanoconducting layer

Recently, the interaction of electromagnetic waves with conducting interfaces has been studied and several applications have been proposed. In these structures a free two-dimensional interface charge layer is generated at the dielectric interfaces and interesting phenomena are observed. In this paper, the effect of finite charge layer thickness and its asymptotic behaviour towards the conducting interface, where the thin charge layer is modelled via a surface conductivity σ, is thoroughly studied for the first time. Two different regimes are considered: first, propagation of optical waves through subwavelength free charge layers and their corresponding reflection and transmission coefficients for both major TE and TM polarizations are considered; second, optical slow waves localized at the interface of two dielectrics with an interface charge layer between them and their corresponding effective index of propagation are investigated. The sensitivity of wave propagation through such structures is briefly discussed and some special cases are discussed in more detail. The electromagnetic response of optical filters based on surface wave excitation at the conducting interface is reexamined with due account of the nonzero conducting layer thickness. © 2006 IOP Publishing Ltd.