Anomalous spectral shifts in plasmonic nano-cavities

Abstract

Nanoplasmonics have the ability to confine light in extremely small nano-cavities. We show using a theoretical model, numerical calculations and measurements that for these tightly-coupled nanoplasmonic structures, the correlation between the field enhancement (near- field) resonance and the radiative (far-field) resonance breaks down. This dissociation is determined by the nanocavity’s geometry. The anomalous behaviour of plasmonic nanocavities is of significant importance for active and quantum plasmonics, where extreme nano-cavities are essential to observe strong coupling.