Tunable polarization-nonsensitive electromagnetically induced transparency in Dirac semimetal metamaterial at terahertz frequencies

Tunable polarization-nonsensitive electromagnetically induced transparency (EIT) based on Dirac semimetal films (DSF) at terahertz frequencies is numerically studied in this paper. We first numerically investigate the EIT effect in a DSF-based terahertz metamaterial structure comprising a DSF strip and two DSF L-shaped resonators. To achieve the polarization-nonsensitive EIT effect, we introduce one vertical strip and two more L-shaped resonators to the above structure. The transmission spectra of the new structure show strong polarization-nonsensitive characteristic because of the fourfold symmetry. By analyzing the surface currents and electric field distribution at the resonant frequencies, we demonstrate that an EIT effect arises from the bright-bright mode coupling. Moreover, the polarization-nonsensitive EIT structure exhibits a blue shift with the increase in the Fermi energy of the DSF without having to re-optimize its geometrical parameters. Our study opens a new path for developing terahertz devices such as terahertz switches. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement