Anisotropic Metasurface for Orbital Angular Momentum Generation with Controlled Polarization

In the past few years, the orbital angular momentum (OAM) has aroused great interests within scientific communities, showing great potentials to enhance capacities in radio, optical and quantum communications. Here an anisotropic coding metasurface is proposed to generate the OAM vortex beam and control its polarization state at microwave frequencies. By tailoring the geometries of subwavelength meta-atoms, the reflection phases in x and y polarizations can be engineered and encoded independently. This allows us to control the eventual polarization state of the generated OAM vortex beam by engineering the phase difference of the element toward both polarizations. The simulation results demonstrate that the OAM vortex beam can be generated as expected, with polarization state in a controlled manner. The proposed method shows great potentials for the application of polarization division multiplexing in OAM communication systems.