Purcell factor for plasmon-enhanced metal photoluminescence

We develop a theory for plasmonic enhancement of metal photoluminescence (MPL) in metal nanostructures. In such systems, the primary mechanism of MPL enhancement is excitation of localized surface plasmons (LSP) by recombining carriers followed by LSP radiative decay. For plasmonic structures of arbitrary shape, we derive explicit expressions for the MPL Purcell factor and MPL spectrum in terms of metal dielectric function and the LSP frequency. We find that the interference between the direct and LSP-mediated processes explains the blueshift of MPL spectral peak relative to the LSP resonance in scattering spectra observed in numerous experiments.Comment: 6 pages, 2 figure

Transition to strong coupling regime in hybrid plasmonic systems: Exciton-induced transparency and Fano interference

We present a microscopic model describing the transition to strong coupling regime for an emitter resonantly coupled to a surface plasmon in a metal-dielectric structure. We demonstrate that the shape of scattering spectra is determined by an interplay of two distinct mechanisms. First is the near-field coupling between the emitter and the plasmon mode which underpins energy exchange between the system components and gives rise to exciton-induced transparency minimum in scattering spectra prior the transition to strong coupling regime. The second mechanism is Fano interference between the plasmon dipole and the plasmon-induced emitter's dipole as the system interacts with the radiation field. We show that the Fano interference can strongly affect the overall shape of scattering spectra, leading to the inversion of spectral asymmetry that was recently reported in the experiment.Comment: 8 pages, 4 figure