Aperture partitioning holographic metasurface for the generation of a directional vortex beam

In this paper, what we believe to be a new aperture partitioning holographic metasurface is designed to effectively generate a directional vortex beam with mixed orbital angular momentum (OAM) modes. The proposed holographic metasurface consists of four adjacent doughnut-shaped regions, and a monopole probe is set in the center for feeding. These four well-designed regions generate four different OAM mode numbers of -1, -2, -3, and -4 respectively, and thus realize a directional vortex beam with mixed OAM modes. The proposed holographic metasurface operating at 10 GHz is simulated, fabricated, and measured. The measurement results agree well with the simulation results. The realized directional vortex beam contains both beam directionality and rich vortex phase vibrations property, which makes it useful in improving vortex beam transmission distance and applications in Multiple-Input Multiple-Output (MIMO) communication systems.