Optical activity and applications of planar chiral metamaterials

The polarization and intensity behaviours of optical planar chiral metamaterials have been investigated in order to further understand the fundamental mechanisms that produce optical activity in these materials, and to seek applications for the unique properties that they offer. A range of planar chiral metamaterials were fabricated using electron beam lithography, reactive ion etching and lift-off techniques to produce high densities of complex planar chiral patterns distributed over large areas on silicon and silica substrates. A range of materials have been used to form the active layer of the planar chiral metamaterials. Planar chiral metamaterials produced using all metallic and dielectric layers are found to induce large changes in the polarization state of first-order reflected and transmitted beams. The anisotropic optical activity in higher-order diffracted beams is sensitive to both the two-dimensional chirality and the thickness of the patterned layer. These results provide further evidence of the role of planar chirality in determining the direction and magnitude of the polarization changes observed in planar chiral metamaterials. Meanwhile, the dependence of the polarization response of the first-order diffracted beams on the thickness of the active layers and the lack of activity of samples where chiral patterns were simply etched into a substrate, suggest that thin film interference has a significant role in the mechanisms that determine the optical activity of all planar chiral metamaterials.