Transforming Surface Wave to Propagating OAM Vortex Wave via Flat Dispersive Metasurface in Radio Frequency

In this letter, we propose an approach to generate and transform surface wave to orbital angular momentum (OAM) vortex wave using flat dispersive metasurface. The metasurface cell is a ring-surrounded bowtie patch, which is specifically designed for controlling the phase of the scattered fields. The phase response of every metasurface cell is optimized to meet the phase compensation required for generating OAM wave. The metasurface array operating at 10 GHz for generating multiple OAM modes of $\ell = 0$ , 1, and 2, respectively, are designed and fabricated. The simulated and experimental results demonstrate that different OAM modes can be generated. The near-field and far-field features of these arrays are measured, and the transmitting and receiving tests show that different OAM modes are isolated so that they can be used for channel multiplexing.