Effect of rotational symmetry on the optical rotation of using asymmetrical nanostructures

In this paper, we rotate an array of asymmetrical double layer of 4-strips windmill structure to investigate its effect on the chirality and sensitivity detection of biomolecular structures. The structure is made up of silver material with 300nm pitch and 10nm separation between layers. The spectrum shows two resonance modes on 600THz and 900THz with linear polarized light normally incident on the structure. We investigate the CD by rotating one of the layers with respect to the horizontal axis of the other layer by the angle θ. It is observed that the CD spectra at different angles are different. The rotation resulted in larger wavelength shift of the CD spectra. In addition, the CD also increases with the rotating angle given a larger absorption difference between the left and right handed circular polarized light.