Bidirectional multi-mode multiple vortex beams generator based on terahertz metasurface

Herein, we propose a vortex beam generator based on vanadium dioxide (VO2), which can switch between two operating modes (reflection and transmission) to generate bidirectional multi-mode multi-vortex beams across a wide frequency band range of 0.8 THz to 1.6 THz. By leveraging the transition of VO2 from the insulating state to the metallic state with temperature changes, the switching between transmission and reflection modes is achieved. Furthermore, through the application of the convolution and superposition theorem, the multiplexing of orbital angular momentum (OAM) is realized. Our work introduces a new method for multi-channel, multiplexed communication and imaging systems, and offers a novel approach to achieve powerful and flexible regulation of terahertz communication systems.