Optically Active Metasurface with Non-Chiral Plasmonic Nanoantennas

We design, fabricate, and experimentally demonstrate an optically active metasurface of λ/50 thickness that rotates linearly polarized light by 45° over a broadband wavelength range in the near IR region. The rotation is achieved through the use of a planar array of plasmonic nanoantennas, which generates a fixed phase-shift between the left circular polarized and right circular polarized components of the incident light. Our approach is built on a new supercell metasurface design methodology: by judiciously designing the location and orientation of individual antennas in the structural supercells, we achieve <i>an effective chiral metasurface</i> through <i>a collective operation of nonchiral antennas</i>. This approach simplifies the overall structure when compared to designs with chiral antennas and also enables a chiral effect which <i>quantitatively</i> depends solely on the supercell geometry. This allows for greater tolerance against fabrication and temperature effects