Polarization Conversion and "Focusing" of Light Propagating through a   Small Chiral Hole in a Metallic Screen
  Propagation of light through a thin flat metallic screen containing a hole of twisted shape is sensitive to whether the incident wave is left or right circularly polarized. The transmitted light accrues a component with handedness opposite to the incident wave. The efficiency of polarization conversion depends on the mutual direction of the hole's twist and the incident light's wave polarization handedness and peaks at a wavelength close to the hole overall size. We also observed a strong transmitted field concentration at the center of the chiral hole when the handedness of the chiral hole and the wave's polarization state are the same. 
A. V. Krasavin, A. S. Schwanecke, M. Reichelt, T. Stroucken, S. W.   Koch, E. M. Wright and N. I. Zheludev