Terahertz polarization-independent electromagnetically-induced transparency structures

Two simple polarization-independent electromagnetically-induced transparency (EIT) metamaterials are numerically and experimentally demonstrated at the terahertz region. The first structure is composed of two metal concentric rings on a substrate, while the second one is composed of one metal ring with a cross in it. The bright-bright coupling behavior appears in the two symmetric polarization-independent EIT structures while it is generally observed in asymmetrically structures. In addition, the large group index is extracted to verify the slow-light effect of the two EIT structures. These simple EIT structures may have potential applications in certain areas, including sensing, slow-light and filtering devices.