Key points are not available for this paper at this time.
Metasurface holographic imaging offers advantages such as high spatial resolution and precise image reconstruction, making it highly promising for applications in metasurface encryption. However, most microwave metasurface holographic encryption systems operate at a single fixed frequency, failing to fully utilize the frequency degree of freedom in the microwave band. Unlike optical encryption, which has maturely applied frequency multiplexing for security enhancement, our work introduces frequency as a critical degree of freedom to improve the security of metasurface holographic imaging. We achieve frequency multiplexing through physical layer superposition of metasurfaces, proposing a method that uses two metasurfaces to realize holographic imaging at different working frequencies: one single-layer metasurface operates independently at 8 GHz, while another overlay metasurface forms a composite metasurface with the single-layer one to work at 5 GHz. Due to the strong correlation between the composite metasurface and the single-layer metasurface, and the fact that the overlay metasurface carries no useful information, the system exhibits high security and is difficult to decrypt. For image decoding, an XOR dual-verification algorithm is adopted, requiring two rounds of decoding to obtain the final encrypted information, thereby enhancing the system's reliability at the algorithmic level. Experimental results align well with theoretical designs and numerical simulations, validating the feasibility, security, and fault tolerance of the physical layer superimposed dual-band metasurface encryption scheme. This method can be applied to enhance the performance of secure communication and imaging systems.
Li et al. (Wed,) studied this question.