Deformable Perfect Vortex Wave-Front Modulation Based on Geometric Metasurface in Microwave Regime

Perfect vortex (PV) beam, as a novel paradigm to carry orbital angular momentum (OAM), owns constant radius of energy intensity and infinite mode of helical patterns, which overcomes the divergence performances of conventional vortex beam. However, common approaches for PV beam generation require optical cascading systems that should constitute of various lenses and components with bulk volume and high alignment standards, also cannot realize PV customization. Thus, in this paper, we propose a general scheme based on compact platform of geometric metasurface to achieve PV beams generations and deformable wave-front modulations. The adopted unit cell is designed with "ABA"-shaped configuration, which can high-efficiently transform circular polarization incident wave into its cross-polarized state and impose required PV phase patterns. Here, we construct series of metasurface lenses to achieve PVs with eight different OAM modes at operating frequency 10 GHz, and additionally conduct quasi-elliptical energy-ring intensities and fractional modals of PVs by introducing asymmetric periodicity and extra singularities. By exploiting compact metasurface platform, this general scheme for PV beam generation and modulation would provide a theoretical foundation for the electromagnetic waves controlling in modern wireless communication systems.