Broadband asymmetric transmission and polarization conversion of a linearly polarized wave based on chiral metamaterial in terahertz region

A novel chiral metamaterial consisting of double L resonators on two sides of the dielectric substrate is proposed in this paper. The structure can realize broadband asymmetric transmission and polarization conversion of a linearly polarized wave in the terahertz band. The polarization conversion ratio of the linearly polarized wave is more than 80% across a wide frequency range from 2.65 THz to 5.58 THz. Furthermore, the structure realizes three bands polarization angle independent 90° polarization rotator. In addition, optical activity and chirality parameter changing with frequency are studied in detail. The physical mechanism of the polarization conversion is also analyzed by the electric field distributions.