Coupling Bright and Dark Plasmonic Lattice Resonances

TL;DR

This paper demonstrates the coupling of bright and dark surface lattice resonances in 2D plasmonic crystals, resulting in high-Q resonances and a frequency stop-gap, advancing understanding of collective plasmonic phenomena.

Contribution

It introduces a coupled oscillator model to explain the coupling of bright and dark SLRs and reports the highest known quality factors for 2D plasmonic crystal resonances.

Findings

Observation of a frequency stop-gap in SLR dispersion

Formation of narrow standing wave resonances at high frequency edges

Estimation of very high Q-factors (>700) for SLRs

Abstract

We demonstrate the coupling of bright and dark Surface Lattice Resonances (SLRs), which are collective Fano resonances in 2D plasmonic crystals. As a result of this coupling, a frequency stop-gap in the dispersion relation of SLRs is observed. The different field symmetries of the low and high frequency SLR bands lead to pronounced differences in their coupling to free space radiation. Standing waves of very narrow spectral width compared to localized surface plasmon resonances are formed at the high frequency band edge, while subradiant damping onsets at the low frequency band edge leading the resonance into darkness. We introduce a coupled oscillator analog to the plasmonic crystal, which serves to elucidate the physics of the coupled plasmonic resonances and to estimate very high quality factors (Q>700) for SLRs, which are the highest known for any 2D plasmonic crystal.