Real‐time terahertz meta‐cryptography using polarization‐multiplexed graphene‐based computer‐generated holograms

Abstract

Abstract As one of the cutting‐edge technologies in advanced information science, wave‐based cryptography is a prerequisite to enable a plethora of secure encrypting platforms which can be realized by smart multiplexing techniques together with suitable metasurface holograms (meta‐holograms). Here, relying on the polarization multiplicity and re‐writability of a computer‐generated meta‐hologram, a fully secure communication protocol is elaborately developed at the terahertz spectrum to host unique merits for exploring real‐time metasurface‐based cryptography (meta‐cryptography) where highly restricted access of information is imposed. The proposed meta‐cryptography exploits two dynamic near‐field channels of a meta‐hologram whose information can be instantaneously re‐written without any polarization rotation and with high contrast and acceptable frequency bandwidth. The computer‐generated meta‐hologram is constructed based on the weighted Gerchberg–Saxton algorithm via a two‐dimensional array of vertical graphene strips whose anisotropic reflection is merely determined by external biasing conditions. Several illustrative examples have been presented to demonstrate the perfect secrecy and polarization cross‐talk of the proposed meta‐cryptography. Numerical simulations corroborate well our theoretical predictions. As the first demonstration of dynamic THz meta‐cryptography, the meta‐hologram information channels can be deciphered into manifold customized messages which would be instrumental in data storage systems offering far higher data rates than electronic encryption can deliver.

Topics & Concepts