The coupling of multi-channel optical vortices based on angular momentum conservation using a single-layer metal metasurface

Abstract

Optical vortices (OVs) carry the orbital angular momentum with arbitrary topological charges, which has excellent potential in optical communication, photonic integrated circuits, optical trapping, and so on. However, generating arbitrary orders of adjustable optical vortices remains to be solved. Here, we propose a single-layer metal porous metasurface operating in infrared band for generating vortex beams from first to fourth order based on the spin-orbit interactions (SOI). The optical vortices with integral 2π phase are obtained through generating double geometric phase induced by structural element spin rotation. Furthermore, the new phenomenon of optical vortices emerging on the center has also been observed in our system, which is caused by the coupling of multi-channel same-order OVs. Our work possesses wide applications in optical communication, multiplex and demultiplex systems, optical capture devices, and communication coding.