Large molecular fluorescence enhancement by a nanoaperture with plasmonic corrugations

We investigate the influence of circular corrugations surrounding a central nanoaperture to further enhance the fluorescence count rate per emitter and control its emission directionality. Adding a single corrugation already allows to significantly increase the fluorescence signal as compared to a bare nanoaperture. A complete fluorescence characterization quantifies the excitation and emission gains contributing to the fluorescence enhancement process as the number of corrugations is increased.