Directional vortex beam generation through all-dielectric transmission metasurface

Orbital angular momentum (OAM) is an important orthogonal physical dimension for electromagnetic wave's information transmission, and a directional vortex beam provides an insightful and valuable approach to solve the vortex wave's beam divergence problem. However, there have been few effective approaches and devices for such directional beam generation. In this paper, we have proposed a method to achieve the directional vortex beam through metasurface, and performed prototype verification in the millimeter wave band. By appropriately superposing the multiple vortex beams carrying different OAM modes, the directional vortex beam can be realized. A complete design procedure for the directional vortex beam with metasurface is presented, and a shared-aperture all-dielectric metasurface is applied as the hardware implementation. The designed all-dielectric metasurface is simulated, fabricated and measured. The realized directional vortex beam and the OAM modes properties are analyzed and discussed. The proposed method provides an effective way to increase transmission distance and far-field applications of vortex wave, and it can effectively expand the applications of vortex wave in radar and wireless communication.