Optical activity in subwavelength-period arrays of chiral metallic particles

We report on a chirality-induced polarization effect in a planar subwavelength metallic nanograting. We demonstrate that the grating rotates the polarization at normal incidence. Because of the fourfold rotation symmetry, the effect does not depend on the incident beam polarization, but resembles optical activity in isotropic media. We use rigorous diffraction theory to show that polarization effects in the zeroth diffraction order take place in the presence of waveguide resonances with subwavelength-period arrays of chiral metallic particles. (C) 2003 American Institute of Physics.