Multi-degree-of-freedom Metagratings For Information Multiplexing And Steganography Technology

Metasurface is a two-dimensional artificial structure composed of wavelength or sub-wavelength structural units,with its compact structure and powerful functions,it can effectively control the polarization,phase,amplitude,and wavelength of light.The main applications include metalens,metasurface holography,polarization conversion,structural color rendering,vortex beams,polarization beam splitters,etc.This paper studies the information multiplexing and hiding technology of multi-degree-of-freedom metagratings designed by metasurface structure,the main content and research results are summarized as follows:(1)The single-atom metagrating,is a wide-angle,high-efficiency broadband metagrating in the visible light region,based on extraordinary optical diffraction(EOD)theory and detour phase,achieving perfect diffraction.By adjusting the offset distance between the center of the all-dielectric nanorod and the boundary of the meta structure unit,the generated detour phase achieves full coverage of the periodic phase,and combined with the computer-generated hologram(CGH)algorithm,the continuous phase holographic image is demonstrated.Due to its simple structure and outstanding efficiency,the single-atom metagrating provides a model for the practical application of metasurface devices.(2)The diatomic metagrating,based on rigorous Jones matrix analysis and full-wave simulation,can easily achieve almost perfect linear modulation between the polarization/amplitude of light and the sum/difference of diatomic angles,which helps to design the arbitrary polarization angles image multiplexing and hiding applications according to Malus' s law.The experiment verified the image multiplexing of orthogonal and arbitrary non-orthogonal polarization in the all-dielectric metasurface platform in the visible light range,demonstrating the enhanced security and anti-counterfeiting capabilities.In addition,it also demonstrated the function of hiding images with any polarization angle,hiding one image under another,reflecting triple security and anti-counterfeiting.This solution provides a convenient method for improving the security level of optical information hiding and anti-counterfeiting applications.