Measurement of Orbital Angular Momentum by Self-Interference Using a Plasmonic Metasurface

We present a flexible method for measuring the orbital angular momentum (OAM) of a linearly polarized beam by means of a metasurface composed of a V-shaped gold plasmonic antenna. When a linearly polarized OAM light illuminates the metasurface, the ordinary beam with the same polarization and topological charge transmits forward, whereas another two extraordinary beams with the same topological charge but with cross polarization are tilted with respect to the ordinary beam. The topological charge of the OAM beam can be detected by the near-field interferogram of the two extraordinary beams. The metasurface is effective for detecting OAM transparently in a broadband wavelength and offers the capability of integration with fiber and on-chip devices.