A broadband vortex beam generator using graphene metasurface reflectarray in terahertz region

Abstract In this paper, a broadband vortex beam generator based on the graphene metasurface reflectarray is demonstrated in terahertz region. The designed graphene metasurface reflectarray structure realizes the generation of orbital angular momentum vortex wave with topological charges of l = ±1, l = ±2 and l = ±3 ranging from 2 to 2.4 THz by modulating the chemical potential and the radius of the graphene unit. Moreover, all of the vortex beam with topological charges of l = +1, l = +2 and l = +3 have a high purity in the range from 2 to 2.4 THz. Our finding shows that the graphene metasurface reflectarray structure might find applications in the fields of broad band vortex wave devices in THz domains and also provide new insights into innovative low-profile devices in the wireless communication.