Metasurface-based grafted perfect vector vortex beams for high-capacity multi-channel encryption in B5G communications

We propose a metasurface platform for the generation of grafted perfect vector vortex beams (GPVVBs) and a multi-channel optical encryption scheme. The metallic metasurface generates GPVVBs with controllable topological charges via phase grafting. GPVVBs produced by multi-segment phase-grafting configurations exhibit stable and controllable intensity distributions. Experimental and simulated results verify that the proposed metasurface can generate GPVVBs with two- and three-region phase-grafting configurations. The measured results show excellent agreement with simulations, confirming the effectiveness of the design. The multi-channel encryption scheme encodes plaintext into hexadecimal sequences and maps them onto vortex beam patterns. This dual encryption scheme, using topological charge multiplexing, greatly enhances the capacity and security of optical communications and information.