Delocalized lattice plasmon resonances show dispersive quality factors

ABSTRACT: This Letter describes how out-of-plane lattice plasmon (OLP) resonances in 2D Au nanoparticle (NP) arrays show dispersive quality factors. These quality factors can be tailored simply by controlling NP height. Numerical calculations of near-field optical properties and band diagrams were performed to understand the measured dispersion effects of the OLPs. The results revealed that delocalized OLPs are a type of surface Bloch mode composed of many Bloch harmonics. As the OLP dispersion evolves from a stationary state to a propagating state, the nonradiative loss decreases because of weak local field confinement, whereas the radiative loss increases because of strong coupling to the leaky zero-order harmonic. SECTION: Plasmonics, Optical Materials, and Hard Matter Surface plasmon resonances supported in metal nanostruc-tures can concentrate optical fields into nanoscale volumes,1,2 which is important for applications such as plasmonic nanolasers,3,4 optical modulators,5 chemical-bio-logical sensors,6 and nonlinear optical devices.7,8 A slowe