Realizing Full-Spectral Image Encryption in The Infrared Using an Electrically Tunable Metasurface and a Matched Detector

The ability of metasurfaces to manipulate optical waves in the spatial and spectral domain has provided new avenues for the development of compact and secure data storage platforms. Here we present an encryption system consisting of an electrically tunable metasurface and a matched detector for secure encryption of grayscale images in the 8 – 12 μm wavelength range. In the proposed scheme, the encrypted image corresponds to the spatially varying thermal intensity of the metasurface as captured by its matched detector. In contrast to previous metasurface-based encryption schemes, the current approach leverages the full spectral response of the associated photonic devices to achieve secure encryption while circumventing the need for an increased device size. Using examples of single and multi-image encryption, we show that the optical properties of either the metasurface or matched detector alone do not reveal any meaningful information about the encrypted image, thereby validating the security of the proposed scheme. The electrical tunability of the metasurface provides additional security as the image can only be retrieved by operating it at a predefined voltage level. We believe that our results provide intriguing possibilities for the development of compact and secure object tagging and anti-counterfeiting applications in the infrared.