Multi‐Channel Vortex Beam and Grayscale Image Generated by Dynamically Controllable Terahertz Metasurface

Abstract Micro‐nano technology and material science have rapidly evolved, and they lead to the emergence of metasurface. However, there are scarce studies on multi‐channel metasurface to generate orbital angular momentum (OAM) and grayscale image (GI) simultaneously. In this work, the metasurface introduces Malus’ law and spin decoupling to modulate terahertz wavefronts. The designed metasurface consists of the following layers from top to bottom: VO 2 patches, silica spacer, gold patches embedded in the VO 2 layer, silica spacer, and gold substrate. For high‐conductivity VO 2 exhibiting a metallic state, the VO 2 metasurface achieves a vortex beam (VB) with topological charge (TC) of l = 1 under right‐handed circularly polarized (RCP) incidence, and it obtains a VB with a gradient phase and under left‐handed circularly polarized (LCP) incidence. Meanwhile, GI B is observed in the near field under y‐polarized incidence. For low‐conductivity VO 2 exhibiting an insulating state, the gold structure embedded in the VO 2 film takes control of the electromagnetic wave. Metasurface obtains a VB with a gradient phase and in the LCP channel, and it achieves a VB with in the RCP channel. Simultaneously, GI A is shown in the near field under y‐polarized incidence. The vast potential of metasurface for applications in imaging and information processing is demonstrated.