  Plasmonic metasurfaces form a convenient platform for light manipulation at
the nanoscale due to their specific localized surface plasmons. Nevertheless,
despite the high degree of light localization in metals, their intrinsic Joule
losses are often considered prevention from applications in high-quality
dielectric structures. Here, we experimentally demonstrate that in some cases,
the capabilities of plasmonic particles for light manipulation prevail over the
negative impact of absorption. We show the lattice of plasmonic nanoparticles
onto a dielectric waveguide that efficiently couples the light of both circular
polarizations to guided modes propagating in opposite directions. We
demonstrate 80% degree of circular polarization for the out-coupled emission of
GaAs-waveguide-embedded quantum dots. The results allow us to consider the
lattice as a circular-polarization-controlled grating coupler operating at
normal incidence and make this structure prospective for further implementation
as an efficient coupling interface for various integrated devices.
