  Overcoming the diffraction limit to achieve high optical resolution is one of
the main challenges in the fields of plasmonics, nanooptics and nanophotonics.
In this work, we introduce novel plasmonic structures consisting of
nanoantennas (nanoprisms, single bowtie nanoantennas and double bowtie
nanoantennas) integrated in the center of ring diffraction gratings.
Propagating surface plasmon polaritons (SPPs) are generated by the ring grating
and coupled with localized surface plasmons (LSPs) at the nanoantennas exciting
emitters placed in their gap. SPPs are widely used for optical waveguiding but
provide low resolution due to their weak spatial confinement. Oppositely, LSPs
provide excellent sub-wavelength confinement but induce large losses. The
phenomenon of SPP-LSP coupling witnessed in our structures allows achieving
more precise focusing at the nanoscale, causing an increase in the fluorescence
emission of the emitters. FDTD simulations as well as experimental fabrication
and optical characterization results are presented to study plasmon-emitter
coupling between an ensemble of dye molecules and our integrated plasmonic
structures. A comparison is given to highlight the importance of each structure
on the photoluminescence and radiative decay enhancement of the molecules.
