Light coupling and directional emission of spherical gold nanoparticles as nanosensors

In this paper we model accurately spherical gold nano particle (GNP) excited by plane wave sources. The single GNP behaves as an electromagnetic radiator able to transmit energy in a well defined direction. We study the radiation pattern of a single, double and aligned GNPs by changing different parameters such as the dimensions of the GNP, the working wavelength and the polarization of the source. The radiation pattern is studied by means of a properly designed three dimensional finite element method (FEM) approach.The degeneration of the main lobes and the sensitivity of the radiation pattern are observed by varying different parameters such as the working wavelength and the propagation direction of the source wave vector. As usually observed in nanotechnology, GNPs dimensions are not well defined. For this reason, we study criteria to stabilize the direction of the emitted light by analyzing the light emitted from coupled GNPs. The FEM results are validated by an analytical tool suitable for near field evaluation.