Dual-Degree-of-Freedom Multiplexed Metasensor Based on Quasi-BICs for Boosting Broadband Trace Isomer Detection by THz Molecular Fingerprint

The metasurface is a powerful tool for trace analyte sensing in a label-free manner by amplifying their THz molecular fingerprint signals. However, current technologies are still facing the problems of high background noise and narrow working bandwidth. Here, we propose a broadband dielectric metasurface sensor based on guided mode resonances (GMRs) with a dual-degree-of-freedom configuration, which boosts the generation of multiplexed quasi-bound states in the continuum (quasi-BICs). Our design shows the extraordinary sensing performance on molecular fingerprint identification of two trace explosive isomers whose distinctive spectral characteristics span an ultrawide THz band. In comparison to the conventional sensing method, the metasensor demonstrates that the signal enhancement factors of over 19 dB in the entire frequency range from 0.9 THz to 1.6 THz, and is capable of precisely analyzing the sample composition ratios of the two mixed isomers. Our study explores the multiplexing mechanism of quasi-BICs based on the reconfigurable GMR metasurface and facilitates its application on high-sensitivity broadband THz molecular fingerprint retrieval, which is promising for nondestructive detection of trace-amount analytes.