Optical chirality in plasmonic arrays of subwavelength Z-shaped apertures

Optical chirality is reported in a silver thin film with an ordered array of subwavelength Z-shaped apertures. Normal incidence transmission of right-hand circular polarized light through the planar chiral nanostructure is found to be sensitive to the direction of the light propagation resembling well-known circular dichroism phenomenon. The relative transmission difference is increased in the spectral vicinity of the surface plasmon resonances and reaches 0.11. The azimuthal dependences of elliptization of light state are shown to depend upon the direction of light propagation and this effect is also addressed to optical chirality of the specimen. It is experimentally demonstrated that the metamaterial could be substituted for anisotropic lossy medium whose tensors of real and imaginary parts of permittivity are diagonalized in different Cartesian coordinate systems. The angle between these systems is experimentally found to reach 10 degrees in the site of plasmon resonances.