Study on Absorption Enhancement Mechanism and Application of Terahertz Combined Metamaterial

Metamaterial absorber has the advantages of high absorption rate and small size, but its absorption band is very narrow or the number of absorption peaks is limited, which greatly limits its practical application. In this study, a flexible metamaterial composed of a rectangular-ring-rectangle planar array is fabricated, which can realize the absorption of double resonance peaks. The results show that the designed metamaterial absorber has two resonance absorption peaks at 1.04 and 1.92 THz, and the absorption rates are 94.06% and 97.07%, respectively. The maximum sensitivity of the resonance peak 1 is 36.11 GHz/RIU, and the maximum sensitivity of the resonance peak 2 is 91.67 GHz/RIU. Based on the absorption enhancement mechanism of the double absorption peaks of metamaterials, highly sensitive detection of forchlorfenuron was achieved with a limit of detection at 0.01 mg/L. More importantly, the designed metamaterial absorber has also been successfully applied to the detection of forchlorfenuron on the surface of tomatoes, which is in line with the regulations on the maximum pesticide residues in food. The experimental results further prove the feasibility of the designed metamaterial for the detection of biological interfaces and provide a promising sensing platform for the detection of pesticide residues.