Asymmetric transmission through planar chiral photonic nanostructures

Abstract

We report the first experimental observation of the intriguing novel phenomenon of asymmetric transmission in the optical part of the spectrum. In some aspects it resembles the non-reciprocal Faraday effect in magnetized media, but crucially does not require the presence of a magnetic field for its observation. It is radically different from conventional gyrotropy of three-dimensional chiral media (optical activity). The effect was observed in anisotropic planar chiral metallic nanostructures patterned on sub-wavelength scale. This excitation of enantiomerically sensitive plasmons in them manifests itself in an asymmetry of total transmission of circularly polarized light (700-1700 nm) propagating in opposite directions, also found numerically. Furthermore, we show that through chiral symmetry breaking, which allows the excitation of enantiomerically sensitive trapped modes, substantial control over the spectral localization of the effect can be achieved