Guided-Wave Inspired Metasurfaces for Multifunctional Vortex Beam Generation and Manipulation

Vortex beam, manifesting the characteristic helical phase front and amplitude singularity, carries inherent orbital angular momentum (OAM) and has received intensive research from its generation, detection to various promising applications. To flexibly impart OAM to the electromagnetic (EM) waves and further control the topological charge, propagation, polarization, bandwidth and efficiency of the vortex beams, various approaches have been proposed by the science community. In this review, we briefly introduce the established methods for the generation and manipulation of vortex beams, with the focus on the fast-growing guided-wave metasurface based approach. Guided-wave metasurface contains sub-wavelength guided-wave subsystems that are capable of versatile control of the EM wave and we review some recent advances that enabled multifunctional vortex beam generation and manipulation, with an outlook towards the future development in this field. OAM topological charges switching, polarization control, divergence control, full-space vortex beam generation, broadband vortex beam generation and vortex multibeam are covered in this paper aiming to accommodate the ever-increasing demands from the vortex beam applications.