Enhancing the radiative emission rate of single molecules by a plasmonic nanoantenna weakly coupled with a dielectric substrate.

Abstract

Enhancing the spontaneous emission of single emitters has been an important subject in nano optics in the past decades. For this purpose, plasmonic nanoantennas have been proposed with enhancement factors typically larger than those achievable with optical cavities. However, the intrinsic ohmic losses of plasmonic structures also introduce an additional nonradiative decay channel, reducing the quantum yield. Here we report on experimental studies of a weakly coupled dielectric substrate and a plasmonic nanoantenna for enhancing the radiative decay rate of single terrylene molecules embedded in an ultrathin organic film. We systematically investigate how the refractive index of the dielectric substrate affects the lifetime and the quantum efficiency and show that the coupled structure could moderately enhance the radiative decay rate while maintaining a high quantum efficiency.