Chiral optics of planar metamaterials

Any planar structure can be superimposed with its mirror image. Despite lacking conventional chirality, planar metamaterials exhibit stronger and more diverse chiral optical effects than conventional materials. Planar chirality associated with the twist of flat spirals and mirror asymmetry introduced by the direction of illumination give rise to directional transmission asymmetries, giant linear and nonlinear optical activity, circular polarization reflectors and perfect absorbers as well as wavevector selective spectral filters.