Metasurface-based sensor with terahertz molecular fingerprint enhancement in trace additives identification

Terahertz (THz) wave has gained considerable interest in biosensing with its unique spectral fingerprint characteristics. However, limited sensitivity confines its applications in trace-amount identification. In this article, a magnetic dipole metamaterial for strengthening molecular fingerprint in virtue of angle-scanning strategy is proposed, which is carefully designed by elaborately arranging symmetric condition of the dipole structures. The physical mechanism is elucidated by the finite-difference time-domain method. In virtue of manipulating the incident angle, the signal of molecular fingerprint is outstandingly elevated. Consequently, three kinds of food additives including azodicarbonamide, sorbic acid and melamine can be simultaneously detected, and the corresponding identification limits are as low as 1.65 <?CDATA μ g\,cm^ - 2?> μ g c m − 2 , 1.20 <?CDATA μ g\,cm^ - 2?> μ g c m − 2 and 1.66 <?CDATA μ g\,cm^ - 2?> μ g c m − 2 , respectively. Our work offers a new train of thought in identifying trace-amount food additives and paves the way for more practical applications of THz wave in food industry.