Simultaneous Detection of Refractive Index and Temperature in Terahertz Band Based on Electromagnetic Induced Transparency Effect

A dual-parameter sensor based on electromagnetic-induced transparency (EIT) metamaterial is demonstrated for simultaneous detection of refractive index (RI) and temperature in the terahertz band. With a range of RI from 1.2 to 1.4, the RI sensitivities are 172.8 GHz/RIU at low-frequency dip and 220.8 GHz/RIU at high-frequency dip, respectively. With a range of temperature from 308 to 348 K, the temperature sensitivities are 1.617 GHz/K at low-frequency dip and 2.837 GHz/K at high-frequency dip. For a practical application, the sensor is used to measure the thermo-optic coefficient of nonane, with a result of $-6.05\,\,\times \,\,10^{-{4}}\,\,\text{K}^{-{1}}$ . Moreover, the optimal algorithm particle swarm optimization is applied to enhance sensitivities. At low- and high-frequency dips, the RI sensitivities are 234.3 (40 814 nm/RIU) and 276.6 GHz/RIU (66 429 nm/RIU), while the temperature sensitivities are 2.32 (645 nm/K) and 3.42 GHz/K (890 nm/K), respectively. The figure of merit can reach up to 7.782 for RI, while 0.077 for temperature. Our designed sensor has great potential in thermal sensing, optic parameter measurement, and other multiple application scenarios.