High-performance broadband vortex beam generator using reflective Pancharatnam-Berry metasurface

Vortex beam generators, especially for broadband working ones, are essential in recent communication systems, since it is believed to be a key to improve the channel capacity efficiently. However, available vortex beam generators surfer from narrow bands, low efficiencies as well as complex configurations. In this paper, we propose an ultra-broadband reflective Pancharatnam-Berry metasurface to generate the vortex beams within 12-18 GHz. The metasurface consists of 20x20 single-layered rotated reflective elements A Ku-band Archimedes spiral antenna is placed at the focal point of the PB metasurface as a feed source which is used to emit a right-handed circularly polarized wave. Then, the metasurface is fabricated, simulated, and measured. Numerical and experimental results coincided well, indicating that the proposed vortex beam generator demonstrated several improvements, including wideband working (12-18 GHz), high efficiency (75.76%), and simple fabrication. Our findings open up a new avenue for the design of high-performance broadband vortex beam generators.