Terahertz six-channel metasurface for the dynamic modulation of OAM

Abstract Dynamic wavefront modulation enables the performance enhancement of optical devices. Few reseachers have achieved the dynamic wavefront modulation of orbital angular momentum (OAM). In this work, a dynamic modulation of six-channel OAMs is realized. When VO 2 is metallic, the metasurface realizes OAM with a mode of l = − 3 in the left-handed circularly polarized (LCP) copolarized reflection channel. In the right-handed circularly polarized (RCP) copolarized reflection channel, a vortex beam is generated with a mode of l = − 1. In CP cross-polarized reflection channels, OAMs are generated with a mode of l = − 2. Relatively, as VO 2 is insulating, OAM is presented with a mode of l = 1 in the LCP copolarized reflection channel. In the RCP copolarized reflection channel, a vortex beam is achieved with a topological charge of l = 3. In CP cross-polarized reflection channels, the obtained OAMs have a mode of l = 2. As a result, our design has flexible multichannel characteristics. Furthermore, it shows considerable application value in beam shaping and optical encryption.