Controlling the optical spectra of gold nano-islands by changing the aspect ratio and the inter-islands distance: theory and experiment

The absorption spectrum of a dielectric film with periodic array of metallic islands of different shapes and different mutual distances was studied analytically, numerically, and experimentally. We show that the positions of the surface plasmon resonances depend on the nano-structural details. We propose two ways of controlling plasmon resonance frequency: changing the aspect ratio of the elliptical or rectangular islands and changing their mutual distances. A new analytical asymptotic approach for calculating the optical properties of such plasmonic systems is developed. The results of our analytical and numerical studies are in good qualitative agreement with experiment.