High-performance and ultra-broadband vortex beam generation using a Pancharatnam–Berry metasurface with an H-shaped resonator

Abstract Vortex beams carrying orbital angular momentum (OAM) are expected to efficiently increase channel capacity in communication sectors, so ultra-broadband vortex beam generators with high performance are important in next-generation communication systems. Based on the concept of the Pancharatnam–Berry phase, we propose a metasurface with an H-shaped resonator for realizing vortex beam generation within an ultra-wideband frequency range from 7.3 to 21 GHz (relative bandwidth = 96.8%). The designed meta-atom can acquire high efficiency (efficiency ≥ 92%) conversion from the incident plane wave to the reflected vortex wave across the entire frequency band. To verify the performance of the proposed metasurface, a reflective array consisting of 18 × 18 single-layered elements with different rotated angles is simulated for generating the vortex beam with a topological charge of ±2. Through OAM spectral analysis, the left-handed components of the reflected electric fields and mode purity of the generated vortex beams under different frequencies are achieved and discussed in detail. Then the metasurface is fabricated and measured, and the numerical and experimental results coincide well, proving the effectiveness and high performance of the proposed design.