Coupling Tai Chi Chiral Metamaterials with Strong Optical Activity in Terahertz Region

We demonstrated Tai Chi chiral metamaterials of mirror-symmetric and complementary structures in terahertz (THz) region. We investigated the properties of these structures by calculating the transmissions under different circularly polarization waves and analyzing the surface current distributions. The chiral mirror-symmetric structure has circular dichroism and strong optical activity due to electromagnetic field coupling between layers with sub-wavelength thickness. Moreover, the structures with multiple metallic layers or twist angle between layers can realize chirality tunability, which can be used for THz polarized devices. Besides, the complementary structure has potential applications for polarization-insensitive devices in THz region.