Design, simulation, and experimental realization of a high-sensitivity polarization-independent electromagnetically induced transparent terahertz metamaterials.

Electromagnetically induced transparency (EIT) originating from quantum physics can lead to a very narrow-band transparent window, which is sensitive to minor environmental changes. The rational construction of highly sensitive EIT metamaterials facilitates its wide sensing application in the terahertz (THz) range. In this work, we designed what we believe to be a novel polarization-independent EIT terahertz metamaterial sensor composed of four symmetrical Chinese Taichi-like rings and a crossed-shaped structure. The Taichi-like rings excite a high-quality planar toroidal dipole resonator and simultaneously crossed-shaped structure induces electric dipole resonance. The EIT effect is realized by the two strongly coupled resonators. The sensor shows higher sensing characteristics for the ultrathin analyte and refractive index than that of the two resonance models alone. The refractive index sensitivity reaches a maximum value of 331.3 GHz/RIU at a saturated thickness of 10 µm. The sensitivities are higher than that of most reported sensors at the same resonance frequency (range from 0.49 THz to 2.77 THz) and with the same analyte thickness (range from 2 µm to 15 µm). We experimentally fabricated the sensor and demonstrated its fascinating EIT effect. Our results pave the way for the design ideas of new polarization-insensitive and high-performance tuned EIT sensors in the THz band.