Generation of High-Order Bessel Orbital Angular Momentum Vortex Beam Using a Single-Layer Reflective Metasurface

In this paper, we propose a method to generate a high-order Bessel orbital angular momentum (OAM) vortex beam by using a single-layer reflective metasurface, which integrates the advantages of small size, high efficiency, insensitive polarization and stable incident angles. An offset-fed horn configuration is adopted to overcome the feed-blockage effect, and a subwavelength unit cell with rotational symmetry is designed to cover the reflection phase variation range of 360° in different incident angles. The metasurface is simulated, fabricated and measured at the center frequency of 10 GHz, and the results validate that a second-order Bessel OAM vortex beam can be generated effectively. By comparing the field distributions between the Bessel OAM vortex beam and the conventional OAM vortex beam, we find that the generated Bessel OAM vortex beam is obviously more convergent and has more stable field distributions. The single-layer reflective metasurface is simple and flexible to shape the wavefront to be a Bessel OAM vortex wave, which has the potential to be used in a wide range of applications.