An Insulating Oil Refractive Index Sensor Based on Multiband High-Q Terahertz Metamaterials

In order to detect the state of insulating oil with high sensitivity, a multiband high-Q terahertz metamaterial sensor is proposed and fabricated by micro-nano lithography. The research results show that within the frequency range of 0.1-1.8 THz, the sensor has three significant peaks located at 0.644, 1.116, and 1.544 THz, respectively. The sensor with optimized parameters can be used not only as a thickness sensor but also as a refractive index sensor. The sensor exhibits excellent sensing performance at all three resonant frequencies. When the thickness of insulating oil with different refractive is 20 mu m, the frequency shift of the sensor has an excellent linear relationship with the refractive index. The sensitivity reaches 151, 210, and 280 GHz/RIU, respectively, and the Q-factor is up to 482.5. The sensor is tested based on terahertz time-domain spectroscopy (THz-TDS) system. Considering the uncertainties, such as errors, the experimental results agree well with the simulation results. The sensor has the advantages of simple structure, high quality factor, high sensitivity, and strong anti-interference ability. Combined with THz-TDS, it has a broad application prospect in the state detection of insulating oil.