Dynamically tunable multimodal vortex beam generator based on reflective metasurface

Abstract

How efficiently generating a multi-mode vortex beam is the key to the new system of wireless communication technology based on orbital angular momentum. Due to the advantages of simple structure and flexible tunability of the metasurface, in recent years, people have been devoted to generating dynamic orbital angular momentum more simply and efficiently using programmable metasurfaces. To address the current problem of a single number of modes for generating orbital angular momentum vortex beams from metasurface, the programmable reflective metasurface structure has been designed to realize the function of dynamically tunable multi-mode of vortex beams. By loading two varactor diodes inside each metal patch to construct eight digital coding units, and using the programmable bias circuit to modulate the coding distribution and resonance characteristics on the metasurface in real-time, the metasurface obtains low reflection loss and stable reflection phase, and finally obtains vortex beams with mode numbers of ℓ = ±1, ℓ = ±2, and ℓ = ±3, respectively. The designed metasurface also has the advantages of a simple structure, small electrical size, and low profile, which has a large potential value in the communication of vortex beams and a perfect application in wireless transmission.