Generation and Measurement of a Bessel Vortex Beam Carrying Multiple Orbital-Angular-Momentum Modes through a Reflective Metasurface in the rf Domain

We discuss the generation and measurement of a Bessel vortex beam carrying multiple orbital-angular-momentum (OAM) modes in the radio-frequency domain. Considering that a high-order Bessel beam inherently has high-order OAM modes, in this paper, we propose to superpose these high-order Bessel vortex beams together, which can combine the advantages of the orthogonality of the vortex beam's multiple OAM modes and the Bessel beam's nondiffraction property. A theoretical formula and the basic design method are presented. A reflective metasurface is designed as the beam launcher to generate a deflected Bessel vortex beam that carries two OAM modes of l = 1 and l = 2 simultaneously. The corresponding reflective metasurface is designed, fabricated, and measured. The full-wave electromagnetic simulations and experimental measurements both verify the effectiveness of the design. The proposed method could further promote the application of a Bessel vortex beam in related near-field scenarios such as near-field wireless communication and radar detection and imaging.