Dual-channel grayscale display and encryption by near-field interference of transmitted polarized light on a nanoprinting metasurface

Due to the superior ability to edit the characteristics of light, metasurface has substantial potential in information storage and encryption. As the information carrier, nanoprinting metasurfaces have gained great attention because they can achieve multichannel image encryption in the near-field by rotating the orientation of the meta-atom. However, most existing studies have primarily focused on binary image encryption, which substantially constrains the information entropy and data dimensionality of encrypted content. To overcome this drawback, an optical encoding method using the interference of transmitted polarized light is proposed. Theoretical analysis and experimental results indicate that the nanoprinting metasurface fabricated based on the proposed encoding method can achieve dual-channel grayscale display and encryption in the near field. This study demonstrates a breakthrough enhancement in the information-bearing capacity of nanoprinted metasurfaces, thereby establishing a novel paradigm for high-throughput optical encryption.