Metasurface-enabled polarization-encoded terahertz encryption via angular spectrum intensity modulation.

The exponential growth of communication networks and internet technologies poses severe threats to information security, prompting significant interest in optical encryption as a promising physical-layer solution. Herein, a terahertz encryption framework utilizing an image as an information carrier is presented. In this scheme, information is encoded into a specific Optical Transfer Function implemented via a metasurface, which modulates the carrier's angular spectrum. This architecture uniquely decouples information from the physical hardware, enabling flexible data transmission and digital processing, offering advantages absent in traditional metasurface-based schemes. Security is further reinforced by polarization-dependent decoding, where information retrieval is strictly confined to specific polarization channels. This scheme provides a versatile and robust solution for terahertz encryption.