Fig. 4

Optical encryption demonstration based on cascaded metasurfaces. a The optical microscope images of two arrayed metasurfaces both including 16 × 10 cells which serve as ciphertext. Scale bar: 200 μm. b Information decryption by generating HDPBs through alignment of two metasurfaces according to the customized keys in the form of coordinates (x₁, y₁, x₂, y₂) for four users (each user possesses two keys). c The obtained messages about five parameters of the generated HDPBs and (d) the corresponding retrieved 4-bit Unicode characters based on look-up table. e The decrypted plaintext of four Chinese characters through Unicode encoding by four users