Wang Yuanzhi, He Ying, Qiao Shunda, Duan Xiaoming, Ma Yufei
National Key Laboratory of Laser Spatial Information, Harbin Institute of Technology, Harbin 150001, China.
Sensors (Basel). 2024 Dec 4;24(23):7743. doi: 10.3390/s24237743.
In this paper, a highly sensitive methane (CH) sensor based on light-induced thermoelastic spectroscopy (LITES) and a T-shaped quartz tuning fork (QTF) with hydrogen (H) and helium (He) enhancement techniques are reported for the first time. The low resonant frequency self-designed T-shaped QTF was exploited for improving the energy accumulation time. H and He were utilized as surrounding gases for the T-shaped QTF to minimize energy loss, thereby enhancing the sensitivity of the LITES sensor. Additionally, a fiber-coupled multi-pass cell (FC-MPC) with a 40 m optical length was utilized to improve the optical absorption of CH. The frequency response of the T-shaped QTF with different concentrations of H and He was investigated, and the Q factor in the H and He environment increased significantly. Compared to operating QTF in a nitrogen (N) environment, the signal amplitude was enhanced by 2.9 times and 1.9 times in pure H and He environments, respectively. This enhancement corresponded to a minimum detection limit (MDL) of 80.3 ppb and 113.6 ppb. Under different CH concentrations, the T-shaped QTF-based H-enhanced CH-LITES sensor showed an excellent linear response. Furthermore, through Allan deviation analysis, the MDL of the T-shaped QTF-based H-enhanced CH-LITES can reach 38 ppb with an 800 s integration time.
本文首次报道了一种基于光致热弹性光谱（LITES）的高灵敏度甲烷（CH）传感器以及采用氢气（H）和氦气（He）增强技术的T形石英音叉（QTF）。利用自行设计的低谐振频率T形QTF来延长能量积累时间。将H和He用作T形QTF的周围气体以最小化能量损失，从而提高LITES传感器的灵敏度。此外，采用光程为40 m的光纤耦合多程池（FC-MPC）来提高CH的光吸收。研究了不同浓度H和He环境下T形QTF的频率响应，结果表明在H和He环境中品质因数显著提高。与在氮气（N）环境中工作的QTF相比，在纯H和He环境中信号幅度分别提高了2.9倍和1.9倍。这种增强对应的最低检测限（MDL）分别为80.3 ppb和113.6 ppb。在不同CH浓度下，基于T形QTF的H增强型CH-LITES传感器表现出优异的线性响应。此外，通过阿伦偏差分析，基于T形QTF的H增强型CH-LITES在800 s积分时间下的MDL可达38 ppb。
