Tuning concept and design criteria of efficient planar metallic plasmon waveguides using nanocomposite materials for electromagnetic radiation applications

In this paper we propose a useful approach to enhance a surface plasmon wave (SPW) in a planar metallic waveguide obtained by nanocomposite materials. We prove analytically and experimentally that SPW propagates on the metallic surface and decays along the longitudinal direction of the plasmon waveguide. We develop a theoretical model based on the tuning of the effective permittivity index of a polymer film containing gold particles ranging from nano to micro scale. The tuning concept is based on the control of gold particles concentration in the polymeric film. The model starts from the accurate Brendel-Bormann (BB) method for the evaluation of the complex permittivity of metals and evaluates the cross section extinction and scattering by tuning the concentration of gold in a polymer film instead of metallic layer. Assuming the distance of gold nanoparticles (GN) small compared to the working wavelength, each particle behaves as an oscillator which is able to couple and transfer the SPW along the whole polymeric film layer as happens for thin metallic films. Under the hypothesis of uniform distribution of spherical GN in the nanocomposite material, the model shows the design criteria for high radiation efficiency of GN placed in the plasmon surface and coupled with the SPW. In order to highlight the importance of the dimensions of the GN concerning the light scattering process, we analyse the electromagnetic radiation pattern of GN characterised by different dimensions and excited by the resonant SPW obtained by the proposed model. The radiation pattern of spherical micro/nano particles is studied by means of a three dimensional (3D) finite element method (FEM). A good agreement between FEM and analytical results is found. Copyright © 2011 American Scientific Publishers.