Fig. 4: Schematic illustration of the optical nested encryption and demonstration of the code charts.
From: Angular momentum holography via a minimalist metasurface for optical nested encryption
a Conceptual illustration of the optical nested encryption scheme based on the AM meta-hologram. The optical information is successively encrypted by the two kinds of independent holography, which are represented by a red lock and a green lock, respectively. b, d Demonstration of code chart I and III, with the SOL and SS holographic images are translated to constitute keys for next decryption, respectively. c, e Demonstration of code chart II and IV, where the alphabet from A to Z are encoded. The coding rule is that each letter corresponds to a union set of two holographic images
