High-security optical encryption using spin-orbital angular momentum matched structure light beam modes

Abstract Affording the unique attributes of parallel processing, high-speed operation, and multi-dimensional manipulation, optical encryption has garnered attention as an excellent candidate for high-security information encoding and decoding. However, existing optical encryption schemes that employ common photonic dimensions like wavelength, polarization, and angular momentum are subject to an upper encryption limit of O(2 N ), significantly hampering the development of information security. To overcome this limitation, we present a novel high-security optical encryption approach, which leverages the spin-orbital angular momentum matched structure light beam (SLB) modes as information carriers beyond conventional photonic dimensions. By flexibly encoding two complementary holographic images onto the spin eigen-components of SLB modes with a segmentation mapping method, this approach conceals the authentic information within an infinite orthogonal space, thereby facilitating the enhanced encryption complexity from a linear to an exponential level O(2 N 2 ). To demonstrate this concept, we developed a dielectric-type metasurface and conduced three distinct encoding strategies for optical encryption utilizing diverse SLB modes, each demonstrating strong robustness and high fidelity. Our findings substantiate the efficacy of the proposed strategy in enhancing the security level of optical encryption, which may benefit advanced applications such as all-optical information encryption, steganography, and optical camouflage.