Mimicking longitudinal MOKE with metasurfaces

Specular optical activity manifests itself as the rotation of light polarization when reflecting from chiral materials and diffusive scattering from chiral liquids. The effect is generally extremely weak, especially in the visible domain. Here we demonstrate strong specular optical activity at the wavelength of 660nm in achiral non-magnetic metasurfaces featuring nano-scale periodic slit patterns milled into a gold film. We reveal through experiment and simulations that the metasurfaces with reduced structural symmetry are able to induce directionally dependent polarization rotation with magnitude of ~1°, which mimics longitudinal MOKE in magnetized films.