Optical encryption by dynamically modulating the spatial frequency of light fields

Abstract

Optical encryption has received increasing attention recently as information security is playing a crucial role in the modern information society. Particularly, the intensive investigation and rapid development of metasurfaces have significantly facilitated the research of optical encryption with enhanced security and increased capacity for information. Nevertheless, most metasurface encryption schemes still suffer from the challenge of dynamic modulation. Here, we demonstrate a novel dynamic optical encryption scheme in which information can be encrypted in light fields in a reconfigurable manner. Specifically, the spatial frequencies of optical images are utilized as information carriers and dynamically modulated for encrypting information. With the developed reconfigurable Fourier optics technique, various kinds of messages can be directly embedded in the spatial frequency domain of the ciphertext images and maintained with high fidelity. Importantly, information security and capacity can benefit from high-speed dynamic modulation with advanced coding techniques, an example of which has been demonstrated via exploiting the position, profile, and time degrees of freedom of spatial frequency. The proposed novel optical encryption scheme may pave the way for realizing high-performance information encryption systems.