Surface plasmon-polariton mediated enhancement of the emission of dye molecules on metallic gratings

We present measurements of iso-frequency dispersion surfaces of light scattered from metallic micro-gratings with different periods. The dispersion surfaces, obtained using an infinity-corrected microscope objective, exhibit maxima attributed to diffracted orders as they become evanescent and pronounced minima due to the resonant excitation of surface plasmon polaritons (SPPs). We have also measured the enhanced photoluminescence of a thin layer of dye molecules on top of the grating. This enhanced luminescence is attributed to the local field enhancement close to the surface due to the coupling of the excitation frequency to SPPs. Moreover, we obtain a directional emission of the luminescence, which is attributed to the grating-assisted coupling of SPPs excited by the dye to free space light. The technique used for the measurements presented in this paper can be extended to characterize the angular emission patterns of emitters coupled to micro- and nano-plasmonic structures.