Cascaded metasurface for separated information encryption[Invited]

For a conventional cascaded metasurface,the combination channel and each single channel are mutually dependent because the phase modulation of a cascaded metasurface is the sum of each single one.Here we propose a cascaded metasurface that can independently encode information into multiple channels.Based on the orientation degeneracy of anisotropic metasurfaces,each single metasurface can produce a quick-response[QR]image in the near field,governed by the Malus law,while the combined channel can produce a holographic image in the far field,governed by geometric phase.The independent and physically separated trichannel design makes information encryption safer.