Hybridized plasmon modes in a system of metal thin film–nanodisk array

Controlling the hybridization is a very powerful tool to manipulate the modes in a single nanostructure. We investigate the hybridization between localized and propagating surface plasmons in a nanostructure system where a thin metal layer strongly interacts with a nanodisk array. Hybrid plasmon resonances are observed in the reflection spectra obtained from finite-difference time domain simulations and experimental measurements in the visible-near-infrared region. We demonstrate how the geometrical parameters of the nanostructure can be utilized to bring these plasmon modes in the strong coupling regime. The hybrid plasmon modes exhibit anticrossing with a Rabi splitting of ∼ 0.1 eV, which is the signature of strong coupling. Near-field profiles of the hybrid modes exhibit a mixture of localized and propagating plasmon characteristics, with propagating modes excited on both sides of the metal film. Our design promises richer implementations in light manipulation towards novel photonic applications compared to the systems with thick metal films.