Enhanced optical encryption via polarization-dependent multi-channel metasurfaces.

Optical encryption offers a powerful platform for secure information transfer, combining low power consumption, high-speed transmission, and intuitive visualization. Metasurfaces, with their unprecedented ability to manipulate light across multiple degrees of freedom within quasi-two-dimensional nanostructures, are emerging as promising devices for advanced encryption. However, encryption capacity remains constrained by limited information channels. Here, we present a visual secret sharing (VSS) scheme utilizing metasurfaces with multiple polarization-dependent channels and minimized crosstalk. Using a global optimization strategy for nanostructure geometries across the entire metasurface, we successfully realize eight independent polarization channels with negligible crosstalk. By encoding both the key and information into these channels with a modified VSS scheme, we demonstrate the complete recovery of seven plaintexts. This strategy supports scalable, high-capacity encryption, and can incorporate additional optical degrees of freedom, offering advanced solutions for advanced secure communication, information storage, and anti-counterfeiting.