Broadband cross-polarization conversion by symmetry-breaking ultrathin metasurfaces

We demonstrate theoretically and experimentally a plasmonic metasurface operating as a broadband polarization converter with adequate efficiency which can transform linearly polarized light into its orthogonal polarization in the near-infrared region. The unit cell of the specifically designed metasurfaces is composed of an asymmetric split-ring resonator (SRR) within a square metallic hole. The adequate polarization conversion rate arises from the enhancement of the cross-polarized electric field and the decrease in the co-polarized electric field induced by the symmetry breaking of the SRR. Furthermore, a broad operating frequency range results from the overlap of multiple polarization rotation responses, which are generated in the combined symmetry-breaking SRRs and square metallic holes. This ultrathin single-layer metasurface avoids the complicated fabrication process of multilayered and tridimensional polarization converters and offers more intriguing possibilities to design high-performance plasmonic metasurfaces for polarization modulation. Published by AIP Publishing.