Four-channel display and encryption by near-field reflection on nanoprinting metasurface

Abstract

Multichannel metasurfaces become one of the most significant development trends, as they exhibit versatile manipulation abilities on electromagnetic fields and provide a promising approach to constitute compact devices with various complex functions, especially in optical encryption due to its capabilities of multichannel, high complexity, and high concealment. However, the existent multichannel metasurfaces based optical encryption technology can only realize two channels in the near-field, or perform three channels in near- and far-field. In this paper, a four-channel display metasurface used to encrypt information by three optical parameters as security keys is firstly proposed and experimentally demonstrated, which is different from the previous three-channel metasurface combined nanoprinting and hologram in near- and far-field. The novel design strategy of the four-channel metasurface can effectively enhance the information capacity and increase the difficulty of leaks without causing manufacturing challenges and additional costs. In addition, the simulation and experimental results demonstrate that the designed metasurface with four independent channels can separately display distinguishable nanoprinting images under decoding keys of special optical parameters. The proposed four-channel display metasurface with advantages of high capacity and ultracompactness will pave a way for multichannel applications in nano display, information storage, optical anticounterfeiting, and other relevant fields.

Multi‐Channel Image Encryption Based on an All‐Dielectric Metasurface Incorporating Near‐Field Nanoprinting and Far‐Field Holography

“…When the polarization direction changes, the image at the encryption channel will be distorted and the correct image information will be filtered out (more details are described in Note S5, Supporting Information). Because of the design principle of multi-channel nanoprinting image encryption, there exists some crosstalk between the images in different channels, [31,32] but the image fidelity is still well to a certain extent. In addition, we calculated the broadband transmittance (400-700 nm) curve for the entire encryption metasurface.…”

“…As 2D artificial metamaterials, metasurfaces, which have the advantages of being ultrathin and ultracompact, have shown flexibility in regulating the polarization, amplitude, and phase of light on the subwavelength scale. [7][8][9][10][11] By appropriately designing the distribution of scattered nanounit structures, metasurfaces can be used for optical elements with various functions, such as orbital angular momentum, [12][13][14][15][16][17] optical switching, [18][19][20] spin Hall effect, [21][22][23][24] beam focusing, [17,[25][26][27] nanoprinting, [28][29][30][31][32][33] and holographic imaging. [4,[34][35][36][37][38][39][40][41] Recently, metasurfaces have exhibited significant potential in miniaturized and high-security information encryption devices owing to their small size, high resolution, and low manufacturing cost.…”

Multiplexing Optical Images for Steganography by Single Metasurfaces

“…In this multiplexing optical image steganography case, some secret information can be embedded into a media and extracted by multiple receivers with specialized keys. [23,[35][36][37] In this paper, we proposed a new strategy to generate multiplexing optical image steganography using a single metasurface, consisting of simple nanorods with different in-plane orientation angles. This strategy is to introduce optical image steganography into the design process of multifunctional metasurface to transfer multiplexing secret information to different receivers, where each independent secret information can be extracted by a corresponding key.…”

“…In this multiplexing optical image steganography case, some secret information can be embedded into a media and extracted by multiple receivers with specialized keys. [ 23,35–37 ]…”

Experimental Implementation of Metasurfaces for Secure Multi‐Channel Image Encryption in the Infrared

“…The majority of the proposed metamaterials encode image‐based information in the form of holograms on predefined spectral and polarization channels. [ 12–27 ] However, the encoded images are easily recovered by using the correct illumination, undermining the security of data storage.…”