Abstract
We present a systematic experimental study on the optical properties of plasmonic crystals (PlC) with hexagonal symmetry. We compare the dispersion and avoided crossings of surface plasmon modes around the Γ-point of Au-metal hole arrays with a hexagonal, honeycomb and kagome lattice. Symmetry arguments and group theory are used to label the six modes and understand their radiative and dispersive properties. Plasmon-plasmon interaction are accurately described by a coupled mode model, that contains effective scattering amplitudes of surface plasmons on a lattice of air holes under 60°, 120°, and 180°. We determine these rates in the experiment and find that they are dominated by the hole-density and not on the complexity of the unit-cell. Our analysis shows that the observed angle-dependent scattering can be explained by a single-hole model based on electric and magnetic dipoles.
Highlights
The interaction between surface plasmons (SPs) and nano-structures is an active field of research [1,2,3,4,5,6]
In this paper we study 104 holes simultaneously and retrieve more accurate information on the scattering process of individual holes than what is possible with single hole experiments
While the square lattice is two-dimensional, the observed intensity and phase of the laser beam can be described by a one-dimensional model [10]
Summary
The interaction between surface plasmons (SPs) and nano-structures is an active field of research [1,2,3,4,5,6]. Lattices of such nano-structures form optical meta-materials [5, 7]. Such materials can be designed and engineered despite the fact that the interaction with a single subwavelength circular nanohole in a gold film cannot be described accurately using simple theory. Near-field experiments on a single isolated hole provided more insight in such SP-hole scattering process [8], but leafs questions about the interaction between holes and the size variations that occur in arrays unaddressed. Metal-hole arrays with a square lattice and an active layer show SP-laser action [9]. A first step in this process is to determine the SP-bandstructure of such hexagonal based lattices, where the scattering properties of a single hole form a key ingredient
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