Mechanism of the large polarization rotation effect in the all-dielectric artificially chiral nanogratings.

The physical mechanism of the large polarization rotation effect in direct transmission of the all-dielectric artificially chiral nanogratings is explored by experiment and numerical analysis. It is shown that the different coupling of right- and left-circularly polarized components of the normally incident light to the leaky guided modes or Fabry-Pérot resonance modes lead to the enhanced circular dichroism, resulting in the giant polarization rotation effect. The mode profile and local field calculations demonstrate intuitive images of the different coupling performance at resonances.