Continuous and precise modulation of vortex beams based on terahertz full-space coding metasurfaces.

Vortex beams carrying orbital angular momentum (OAM) exhibit excellent potential for applications in fields such as sixth-generation communication, quantum information processing, and imaging technologies. However, the realization of multi-mode and full-space continuous precision modulation of vortex beams still faces significant challenges. In this study, a terahertz full-space coding metasurface based on vanadium dioxide (VO) is proposed, combined with a more accurate generalized coding strategy, convolution, and generalized superposition methods to achieve continuous and precise modulation of vortex beams. First, the phase state of VO is dynamically adjusted by temperature changes, enabling the coding metasurface to switch between transmission and reflection operating modes. Second, a precise generalized coding strategy is developed to support the generation of coding sequences for arbitrary values by logically discretizing the size of the super-subunit. Meanwhile, by convolving different coding sequences, continuous and precise modulation of different modes of vortex beams in the range of 0 to 360° is realized. Finally, the deflection vortex beams carrying different OAM are effectively superimposed using the generalized superposition method. This innovative coding strategy significantly improves the ability of continuous and precise modulation of the vortex beam wavefront, laying a solid foundation for future breakthroughs in intelligent communication and high-resolution imaging technologies.