Dispersion-flattened transmission based on liquid-crystal-coated plasmonic subwavelength structures

Recently, noble metallic annular aperture arrays (AAAs) have drawn considerable attention due to their peculiar properties and great potential for ultracompact optical applications. AAAs have been experimentally confirmed to have much higher peak transmission than simple hole arrays with the same open area. Here, gold AAAs with overlapped apertures are reported. We show that different shapes of nanopillars can be formed by controlling the inner and outer radii, thus affecting the plasmonic properties of the nanostructures including both localized surface plasmon resonances (LSPRs) and surface plasmon polaritons (SPPs). By overlaying a layer of liquid crystals onto these plasmonic nanostructures, a pronounced optical transmission with a broad top-flat passband is observed. This unique property makes such a hybrid device potentially useful for broadband optical filters.