Surface Lattice Resonances in Plasmonic Arrays of\nAsymmetric Disc Dimers

Abstract

We\nstudy regular wavelength scale arrays of metallic dimers. By\nemploying dimers made up of two different sized discs, we are able\nto couple to array-based collective surface lattice resonances of\nboth bright and dark, that is symmetric and antisymmetric, dimer modes\nand to show that the degree of asymmetry can be used to control the\nrelative strength of the two surface-lattice modes. The collective\nnature of these excitations can even lead to an antisymmetric surface-lattice\nresonance that is stronger than the symmetric one; this is in stark\ncontrast to the dark and bright nature of the underlying modes of\nthe individual dimers. We verify these experimental findings, derived\nfrom extinction measurements, by comparison with both analytical and\nnumerical modeling.