Purcell factor for plasmon-enhanced metal photoluminescence

Abstract: We present an analytical model for plasmonic enhancement of metal photoluminescence (MPL) in metal nanostructures with characteristic size below the diffraction limit. In such systems, the primary mechanism of MPL enhancement is excitation of localized surface plasmons (LSP) by recombining carriers followed by a photon emission due to LSP radiative decay. For plasmonic nanostructures of arbitrary shape, we obtain a universal expression for MPL Purcell factor that describes the plasmonic enhancement of MPL in terms of metal dielectric function, LSP frequency, and the system volume. We find that the lineshape of MPL spectrum is affected by the interference between direct carrier recombination processes and those mediated by plasmonic antenna which leads to a blueshift of MPL spectral band relative to LSP resonance in scattering spectra observed in numerous experiments.