There is a strong current interest in nanoscale metal-dielectric particles and assemblies due to their highly unusual optical properties, which are governed by the hybridization of plasmonic resonances. Their broad application areas include photonics, biomedical sensing, catalysis and molecular spectroscopy. Recently metal-dielectric nanostructures found applications in the design of magnetic (optical) metamaterials – novel class of artificial medium with strong magnetic response to the incoming electromagnetic radiation. Such materials are experiencing booming research interest stemming from their remarkable and sometimes counterintuitive properties, including superlensing and electromagnetic cloaking. Most importantly, the operation frequencies of such magnetic metamaterials have recently entered the visible range [1].
Here we present a nanoscale surface-supported metal-dielectric geometry – a ‘nanosandwich’ structure with two metallic (Au, Ag) nanodisks separated by a dielectric layer – with resonant optical response defined by plasmon coupling (hybridization). The latter is the key phenomenon, producing a bimodal plasmonic resonator, easily tunable at optical frequencies [2]. Due to efficient optical excitation of both in-phase and out-of-phase coupled plasmon oscillations such nanostructures show significant magnetic resonance. The nanosandwiches are produced by self-assembly technique that allows for cost-effective fabrication over large areas on a variety of substrates, which makes the structures directly applicable for the design of novel functional nanoscale architectures, like optical metamaterials.
[1] V. M. Shalaev, Nat. Phot. 1, 41 (2007); C. M. Soukoulis et al., Science 315, 47 (2007).
[2] A. Dmitriev et al., Small 3, 294 (2007); T. Pakizeh et al., Opt. Exp. 14, 8240 (2006).
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