Leveraging Correlations between The Statistics and Spectral Properties of Random Metasurfaces for Multi-Wavelength Cryptography

Randomness and disorder are abundant in nature and help in sustaining the environment around us. In particular, random optical media encountered in various varieties of insects, birds and marine organisms are naturally optimized to offer survival advantage in their respective habitats. Historically, photonics researchers have focused their attention on periodic and ordered systems, and randomness has often been viewed as undesirable. In recent years, the broad range of functionalities exhibited by random optical media have prompted researchers to explore materials with tailored disorder for various applications. As opposed to their periodic counterparts, the vast design space afforded by disordered photonic devices provides greater flexibility in achieving tailored optical responses. However, the expanded design space makes it challenging to map the structural degrees of freedom of random photonic devices to their optical properties. This necessitates the identification of a tractable set of parameters that can be used to characterize random optical media. Here, we investigate correlations between the configuration statistics of random metasurfaces and their spectral response. Our metasurfaces consist of a two-dimensional array of silicon nanopillars with random widths on a silica substrate. We explore the effect of tuning the probability distribution characterizing the nanopillar widths on the wavelength-dependent transmissivity of the random metasurface in the 400 – 800 nm wavelength range. Furthermore, we exploit the correlations between the configuration statistics of the random metasurfaces and their spectral properties to design a photonic device encoding spectrally encrypted image data in the visible wavelength range. Our findings offer new insight into the optical properties of random media and provide avenues for developing such systems for a broad range of applications.