%0 Journal Article
%T Field Enhancement in a Grounded Dielectric Slab by Using a Single Superstrate Layer
%A Constantinos A. Valagiannopoulos
%A Nikolaos L. Tsitsas
%J Advances in OptoElectronics
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/439147
%X The addition of a dielectric layer on a slab configuration is frequently utilized in various electromagnetic devices in order to give them certain desired operational characteristics. In this work, we consider a grounded dielectric film-slab, which is externally excited by a normally-incident Gaussian beam. On top of the film-slab, we use an additional suitably selected single isotropic superstrate layer in order to increase the field concentration inside the slab and hence achieve optimal power transfer from the external source to the internal region. We define a quantity of interest, called ¡°enhancement factor,¡± expressing the increase of the field concentration in the film-slab when the superstrate is present compared to the case that it is absent. It is shown that large enhancement factor values may be achieved by choosing properly the permittivity, the permeability, and the thickness of the superstrate. In particular, it is demonstrated that the field in the film-slab is significantly enhanced when the slab is composed by an £¿-near-zero (ENZ) or low-index metamaterial. 1. Introduction Increased field intensity in a localized area is required in a variety of applications from simple traditional implementations to complex state-of-the-art experiments. Indicatively, a resonance plasmon mode, characterized by a substantial local electric field enhancement, has been reported to be formed between a gold nanorod and an infinite slab in infrared range [1]. In addition, the optical trapping force on a spherical dielectric particle for an arbitrarily positioned focused beam has been demonstrated in [2], by using the generalized vector diffraction theory. Moreover, when considering a simple, analytically solvable cylindrical configuration, it has been shown that optical vortices appear which can be used to stably trap particles of particular sizes and index contrasts with the background [3]. Field enhancement of incident near-infrared light has been also investigated in [4], by using the exhibited surface plasmon polariton from erbium ions in a golden film. On the other hand, layered, dielectric slab configurations are commonly used in electromagnetic (EM) devices since they possess certain functional advantages such as conformability and ease of fabrication. In particular, dielectric layers, with carefully selected physical and geometrical parameters, are extensively employed to lend particular beneficial characteristics to the considered devices. In [5], a multi-layered dielectric coating has been used in semiconductor laser diode optical amplifiers to
%U http://www.hindawi.com/journals/aoe/2012/439147/