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Optical Image Encryption and Authentication Based on Random Phase Encoding and Dielectric Metasurface

An optical image encoding and authentication method based on modified phase retrieval algorithm and dielectric metasurface is proposed. The input secret image is numerically encoded into a noise image based on random phase encoding under the framework of double random phase encoding (DRPE) technique with divergent illumination. It is then transformed into an authenticable POM by using Gerchberg-Saxton (GS) algorithm, from which the diffraction pattern is visibly unrecognizable but comprises sufficient information for authentication. In this method, only a small number of pixels are used to encode the hologram phase information, while authentication results are still obtained successfully. The subwavelength pixel and small total dimension of the POM provide high anti-counterfeiting capability and make it possible to be integrated into an optical integrated system. Computer simulations are presented to demonstrate its good performance.