| Sep 26, 2022 |
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(Nanowerk News) Metasurfaces, composed of nanoresonator arrays with tailored structure and subwavelength feature size, show the potential of manipulating various degrees of freedom for manipulating light, which opens a new door to the field of optical encryption.
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In addition, metasurface holography can encode multiple images on a single metasurface by multiplexing methods, which can improve the information capacity and further realize the applications of encryption, anti-counterfeiting with higher security and fidelity.
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Based on these advantages, researchers in China have now proposed an optical encryption method based on the combination of single pixel imaging and metasurface holography.
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| Schematic illustration of single pixel imaging key for holographic encryption based on metasurface. The red dashed box on the left is the encryption process, and the blue dashed box on the right is the decryption process. The intensity signal and the metasurface are ciphertext, and the pattern sequence in the coding and the subhologram position on the metasurface are used as the key. (Reprinted with permission by Wiley-VCH Verlag)
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They report their findings in Small (“Single Pixel Imaging Key for Holographic Encryption Based on Spatial Multiplexing Metasurface”).
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Through the spatial movement of the metasurface, a large number of patterns required for single pixel imaging can be generated. In addition, a single metasurface can accommodate holograms of 26 letters and 10 numbers, and there is a 50% overlap region between adjacent subholograms in the horizontal direction.
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| Experimental results of nanoholes array metasurface. a) QR code image reconstructed by single pixel imaging based on metasurface. b) Holographic reconstructed image addressed by the string of QR code. (Reprinted with permission by Wiley-VCH Verlag)
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By using the reconstruction image of single pixel imaging as the addressing key, the matching of arbitrary letters and numbers can be realized on holography, which increases the capacity and freedom of information transmission.
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More importantly, due to the existence of overlapping regions between subholograms, more accurate illumination is required to obtain a clear reconstruction image, which greatly meets the security of optical encryption. Through the combination of single pixel imaging and holography, our encryption method can improve the security of encrypted information meanwhile improving the coverage of plaintext information.
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Owing to these excellent characteristics, the team points out that this novel scheme provides a new route to information encryption.
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