Highly tunable optical activity in planar achiral terahertz metamaterials

TL;DR

This paper demonstrates that planar achiral terahertz metamaterials can exhibit tunable optical activity, such as polarization rotation and circular dichroism, due to extrinsic chirality effects influenced by the orientation of the metamaterial and incident wave.

Contribution

It introduces a method to achieve tunable optical activity in nonchiral planar metamaterials through extrinsic chirality, without requiring intrinsic material chirality.

Findings

Tunable polarization rotation observed in terahertz metamaterials.

Circular dichroism achieved without intrinsic chirality.

Extrinsic chirality causes the optical activity effects.

Abstract

Using terahertz time domain spectroscopy we demonstrate tunable polarization rotation and circular dichroism in intrinsically nonchiral planar terahertz metamaterials without twofold rotational symmetry. The observed effect is due to extrinsic chirality arising from the mutual orientation of the metamaterial plane and the propagation direction of the incident terahertz wave.