Resonances of hybridized bound plasmon modes in optically-thin metallic nanoslit arrays for narrow-band transmissive filtering

We present extremely narrow-band transmission of light through optically-thin metallic nanoslit arrays on substrates coated with high/low-index dielectric layers for high-finesse wavelength filtering. The transmission peak is shown resulting from resonances of various hybrid plasmon modes, formed by symmetric or antisymmetric coupling of the symmetric and anti-symmetric bound surface plasmon modes at the ultrathin metal layer with the optical waveguide mode in the dielectric layers. Band-width of the peak can be down to a few nanometers, with no side peaks comparable in transmittance. For the purpose, all structure components have critical roles, clarified with numerical simulations.