ABSTRACT The rapid advancement of information age has created an urgent need for integrated physical‐layer security solutions. We propose a dual‐functional terahertz (THz) encryption metasurface that enables independent information retrieval in both the near field and the far field within a single device. By precisely tailoring the complex amplitude of orthogonal linear polarization components, the metasurface forms two spatially separated far‐field channels for left‐ and right‐handed circular polarizations, which can be accessed simultaneously under linearly polarized illumination and are theoretically free from interchannel crosstalk. In the near field, polarization‐selective amplitude modulation reveals textual patterns, whereas in the far field, phase engineering encodes multiple digital data in focal‐spot arrays under linear, left‐handed, and right‐handed circular polarization states. This compact metasurface provides a scalable route toward THz security tags and robust physical‐layer protection for identification, anticounterfeiting, and high‐capacity wireless communications.
He et al. (Wed,) studied this question.