Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands

We present a plasmonic whispering gallery nanoantenna doped with an ATTO680 dye that shows cavity-modified spontaneous emission. The plasmonic ring antenna consists of a circular groove cavity in a single-crystal Au surface that sustains resonances with different azimuthal and radial mode order. We observe spectral reshaping of the dye emission that can be tuned over a broad band by varying the cavity resonance conditions.