Sensing and slow light properties of dual-band terahertz metamaterials based on electromagnetically induced transparency-like

<sec>Electromagnetically induced transparency (EIT) is a quantum interference phenomenon in a three-level atomic system. The generation of quantum interference effect significantly reduces the light absorptivity of the specific frequency that is strongly absorbed, and produces a sharp “transmission window” in the resonance absorption region. The EIT is usually accompanied by strong dispersion, which significantly reduces the group velocity of light and enhances the nonlinear interaction. The EIT phenomenon of atomic system usually needs to be observed at very low temperature or high intensity laser, which is a very serious challenge for the application of EIT technology. The simulation of electromagnetically induced transparency using metamaterials can effectively break through these limitations.</sec><sec>In this work, an electromagnetically induced transparency-like terahertz metamaterial structure with three bright modes is proposed and investigated. Two weakly hybrid states are composed of two bright modes with similar resonant frequencies. The energy oscillates back and forth between the two modes, and a transparent window is generated between the two resonance points. The designed metamaterial is composed of three groups of bright modes with adjacent resonant frequencies, and the three groups of bright modes are coupled to produce two transparent windows. The electromagnetically induced transparency-like formation mechanism is analyzed based on the simulation curve and electric field distribution. In addition, the sensing properties of metamaterial are determined by simulation and calculation, and the refractive index sensitivities of the two windows can be as high as 451.92 GHz/RIU and 545.31 GHz/RIU under the optimal thickness of the measured substances. Through the sensing simulation of six petroleum products, it is verified that the dual-band has more excellent advantages in dielectric constant matching than the single frequency band. The characteristics of the designed metamaterial in the slow light effect are also studied. The maximum group delay times of the two windows can reach 9.98 ps and 6.23 ps. Therefore, the structure is considered to have an important application value in the field of high sensitivity sensors and slow light devices.</sec>