Generating an orbital-angular-momentum beam with a metasurface of gradient reflective phase

We proposed and experimentally demonstrated a simple metasurface with gradient reflective phase for the generation of an orbital-angular-momentum (OAM) beam. It is easy to design the proposed reflective metasurface by only tuning the patch size to achieve the full-range (2[pi]) reflective phase. Then, the metasurface was constructed by arranging different-sized patches in a proper order to covert a plane wave to an OAM beam. The measured field distribution confirms that the reflected beam from the fabricated reflective metasurface is an OAM beam with central singularity and the phase has 2[pi] change around the center, which is in agreement with the numerical simulations. The proposed reflective metasurface is promising in high-efficient beam manipulation and paves a way to generate the OAM beams for wireless communication applications.