Sensor Based on Infrared Dual-Band Polarization Insensitive Metamaterial Absorber

A sensor based on an infrared dual-band polarization-insensitive metamaterial absorber is proposed, which consists of a square ring layer at the top, a silicon dielectric layer at the bottom, and a metal layer at the bottom. By using the finite element method (FEM), for the transverse electricity (TE) and transverse magnetic (TM) mode incidence, the absorption rates of the resonant point at 4.75 µm are 0.950 and 0.943, and the absorption rates at 7.85 µm can reach 0.997 and 0.998, respectively. Because of the symmetry of the structure, the absorber is not sensitive to polarization when it is vertically incident and can still maintain good absorption performance in a wide range of incidence angles. For commonly used aqueous solutions (sodium chloride, glucose, sucrose, etc.), the refractive index of the aqueous solution is in the range of 1.33 to 1.48 and the sensing test is performed. For the TE mode, the sensing sensitivity is about 2283.05 nm/RIU through linear fitting, and the quality factor Q is 108.38. For the TM mode, the sensing sensitivity is about 2371.43 nm/RIU through linear fitting, and the quality factor Q is 84.50, which has better sensing characteristics. The absorber sensor designed in this paper achieves high sensitivity in the infrared, has a high Q value, is easy to manufacture, and plays a huge advantage in the field of high-sensitivity detection.