Imidacloprid detection using terahertz metamaterial based on electromagnetically induced transparency

Imidacloprid is a common insecticide which can remain in water, soil, and plant parts with long-term consumption, threaten environment and human health. Therefore, it is necessary to propose an effective method for imidacloprid detection. Here, a terahertz metamaterial based on electromagnetically induced transparency (EIT) is theoretically and experimentally demonstrated. This metamaterial displays an EIT resonance at 0.89 THz and the physical mechanism of the EIT effect is investigated by analyzing the electric fields and surface current distribution. The EIT resonance can be modulated by changing the geometric structure parameters of the metamaterial. This metamaterial can be used to detect the thickness and the refractive index of the dielectric layer based on the EIT resonance, and can achieve a refractive index sensitivity of 210 GHz/RIU. The detection of imidacloprid shows that the frequency shift and the transmittance change at peak are depend on the change of imidacloprid concentration. The minimum detectable imidacloprid concentration reaches a level of 0.01 ppm in this case. These results theoretically and experimentally prove the feasibility of terahertz metamaterial based on EIT resonance applied in the detection of imidacloprid concentration.