Theory and simulation of surface plasmon excitation using resonant metal nanoparticle arrays

We discuss a plasmonic coupling device consisting of a periodic array of ellipsoidal silver nanoparticles embedded in SiO2 and placed near a silver surface. By tuning the shape of the particles in the array, the nanoparticle plasmon resonance is tuned. The resulting resonantly enhanced fields near the nanoparticles, in turn, excite surface plasmons on the metal film. We have performed finite integration technique simulations of such a plasmon coupler, optimized for operation near a wavelength of 676 nm. Analysis of the frequency dependent electric field at different locations in the simulation volume reveals the separate contributions of the particle and surface resonance to the excitation mechanism. A coupled oscillator model describing the nanoparticle and the metal film as individual resonators is introduced and is shown to reproduce the trends observed in the simulations. Implications of our analysis on the resonantly enhanced excitation of surface plasmons are discussed. © 2008 American Institute of Physics. DOI: 10.1063/1.2936971