  Two-dimensional lattices of chiral nanoholes in a plasmonic film with lattice
constants being slightly larger than light wavelength are proposed for
effective control of polarization and spatial properties of light beams.
Effective polarization conversion and strong circular dichroism in non-zero
diffraction orders in these chiral metafilms are demonstrated by
electromagnetic simulations. These interesting effects are found to result from
interplay between radiation pattern of single chiral nanohole and diffraction
pattern of the planar lattice, and can be manipulated by varying wavelength and
polarization of incoming light as well as period of metastructure and
refractive indexes of substrate and overlayer. Therefore, this work offers a
novel paradigm for developing planar chiral metafilm-based optical devices with
controllable polarization state, spatial orientation and intensity of outgoing
light.
