Dual Resonant Plasmonic Infrared Pixels for Selective Optical Encoding

Plasmonic metasurfaces allow the optical encoding of information based on bright and non-fading colors with a resolution at the diffraction limit. The optical information is encoded by varying the dimensional parameters of the plasmonic nanostructures, which are then clustered into nanopixels that are parallel and spectrally addressable. The storage density can be further increased by employing asymmetric and polarization-dependent nanostructures. However, further increases in storage density and security capabilities are still vital for the successful implementation of plasmonic metasurfaces as encoding and encryption solutions. Recent progress in infrared hyperspectral imaging has opened up the possibility of covert image encoding. Here, the optical properties of double resonant plasmonic nanostructures are investigated in the mid-infrared. The structures consist of plasmonic nano-antennas that are placed inside resonant plasmonic ring cavities. The associated plasmonic resonances weakly interact, which causes hybridization. However, it is shown that the plasmonic resonances can be nearly independently tuned if the optimal geometry is used and discuss selective and simultaneous optical encoding in mid-wavelength and long-wavelength infrared regions.