Broadband high-purity OAM generator based on metasurface

A pair of mirror-symmetric meta-atom with outer arc and inner E-shaped patch is proposed. The proposed meta-atom can acquire high efficiency above 0.94 and broadband of 98%. When the rotation angle of the meta-atom changes, the reflection phase is varied over 360°and kept good linearity. With such a meta-atom, a reflective metasurface consisting of 18×18 meta-atoms are constructed, which can efficiently generate the OAM vortex beam with l= −2 under left-handed circularly polarized (LHCP) plane wave vertical incidences. The OAM mode purity higher than 66.5% from 7GHz to 22GHz (fractal bandwidth of 103%). Furthermore, the maximum mode purity is 92.2% at 15GHz.