  While long-range propagating plasmons have been extensively investigated for
implementing on-chip optical sensing platforms, waveguide-excited localized
surface plasmon resonance (LSPR) based sensing systems have not yet received
much attention. Waveguide excitation and readout as an alternative to
free-space light based single-particle spectroscopy are particularly attractive
for high-throughput sensing and on-chip drug discovery platforms. Here we
present a numerical investigation of the optical response of a
waveguide-excited plasmonic dolmen-shaped compound nanoantenna that exhibits a
Fano signature in its spectral response. Although only evanescently coupled to
the waveguide, the compound nanoantenna is seen to induce a high-contrast
extinction in the transmission spectrum of the waveguide. The compound
plasmonic nanoantenna configuration presented here is of interest in hybrid
photonic-plasmonic sensing approaches with high-throughput capabilities.
