Based on the metallic-dielectric high contrast gratings, we proposed two new different schemes to achieve the unidirectional coupling of incident free-space light into the plasmonic waveguides. Using the cascaded metal-air subgratings (structure 1) or metallic-dielectric subwavelength periodic gratings (structure 2), the ultra-broadband and wideangular SPPs excitation could be both achieved. The operation principle and performance of the structures are analyzed and discussed, respectively.
A novel optical coupler to access free-space optical signals in subwavelength scale into dielectric waveguide via a
plasmonic concentrator and a dielectric microring with field enhancement is proposed. The coupler is useful as it
combines the plasmonic concentrator, which is used to access optical signals in subwavelength scale, a microring
resonator for the coupling, with the dielectric waveguide for long distance optical transmission and processing.
We theoretically investigate the optical transmission through a subwavelength slit covered with a nanostrip and
surrounded by corrugations in a metal film. Simulations results show that with a nanostrip on top of the slit, the optical
transmission efficiency through the slit surrounded by grooves is greatly enhanced for various angles of incidence
compared with the structure without the nanostrip. The nanostrip should be thick enough to result in an air nanocavity
with high Q value and enhanced transmission efficiency.
We proposed a compact surface wave polarization splitter based on the metallic-dielectric-air (MDA) waveguide with an
slit surrounded by asymmetric corrugations. The incident light coupled to the MDA waveguide through the aperture is
split into TE- and TM-polarized electromagnetic surface modes by the polarization-sensitive corrugations on each side.
Polarization extinction ratios better than 20 dB are achieved for both polarizations. The structure would be interesting for
a variety of optical devices and nanophotonics.