Invited Article: Direct phase mapping of broadband Laguerre-Gaussian metasurfaces

Abstract

We report on the fabrication of metasurface phase plates consisting of gold nanoantenna arrays that generate Laguerre-Gaussian modes from a circularly polarized Gaussian input beam. The corresponding helical phase profiles with radial discontinuities are encoded in the metasurfaces by the orientation of the nanoantennas. A commonpath interferometer is used to determine the orbital angular momentum of the generated beams. Additionally, we employ digital holography to record the detailed phase profiles of the Laguerre-Gaussian modes. This method allows a simple and direct quantitative comparison of the measured phase profiles of the generated Laguerre-Gaussian beams with the theoretically expected phase profiles. Experiments with different laser sources demonstrate the broadband operation of the metasurfacesWe report on the fabrication of metasurface phase plates consisting of gold nanoantenna arrays that generate Laguerre-Gaussian modes from a circularly polarized Gaussian input beam. The corresponding helical phase profiles with radial discontinuities are encoded in the metasurfaces by the orientation of the nanoantennas. A commonpath interferometer is used to determine the orbital angular momentum of the generated beams. Additionally, we employ digital holography to record the detailed phase profiles of the Laguerre-Gaussian modes. This method allows a simple and direct quantitative comparison of the measured phase profiles of the generated Laguerre-Gaussian beams with the theoretically expected phase profiles. Experiments with different laser sources demonstrate the broadband operation of the metasurfaces