Universal terahertz trace molecular fingerprint sensing based on high-degree-of-freedom dielectric metagrating

Label-free molecular detection plays a vital role in the terahertz (THz) field but remains limited by weak light-matter interaction and narrow detection bandwidth, especially for trace analytes. Here, we propose a dielectric metasensor that synergistically couples guided mode resonance and quasi-bound states in the continuum to achieve multimodal enhancement. On this basis, three multiplexing strategies-geometric scaling, incident angle modulation, and waveguide thickness adjustment-are implemented to provide broadband adaptability and structural tolerance. Numerical simulations demonstrate that the "angle multiplexing-thickness compensation" hybrid mechanism narrows the scanning range while effectively enhancing both the resolution and the intensity of fingerprint recognition, with a maximum signal enhancement of 10.69 dB. The method offers a promising pathway for the practical application of THz metasensing in high-throughput biosensing, chemical analysis, and environmental monitoring.