Efficient dielectric metasurface hologram for visual-cryptographic image hiding

Dielectric metasurfaces provide the new freedom to implement information encoding and image hiding with monolayer of artificial atoms instead of bulky optical components to enable wavelength, phase and polarization modulations. We proposed an optical encryption scheme by integrating the Visual Cyptography (VC) with the phase-encoding technique for metasurface. In the encryption process, the secret image is hidden into a group of unrecognizable and mutually-unrelated phase-only meta-holograms with high security of concealment. In the decryption process, the secret image is extracted conveniently by superimposing the reconstructed holographic patterns via directly illuminating the generated meta-holograms instead of complicated holographic exposure facilities and additional cryptographic computations. Different from the general polarization or wavelength encryption of meta-hologram, we use VC to share the secret image into a set of encrypted meta-holograms for the first time, which greatly improves the security of image hiding. In view of the merits of high security, simple decryption and flexible adjustability, we believe it will have significant potential applications in the future optical information security.