Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang 330063, China.
Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, U.K.
Anal Chem. 2021 Nov 23;93(46):15468-15473. doi: 10.1021/acs.analchem.1c03482. Epub 2021 Nov 12.
A laser frequency-locked hollow waveguide (HWG) gas sensor is demonstrated for simultaneous measurements of three isotopologues (CO, CO, and OCO) using wavelength modulation spectroscopy with a 2.73 μm distributed feedback laser. The first harmonic (1) signal at the sampling point where the peak of the second harmonic (2) signal was located was employed as the locking point to lock the laser frequency to the transition center of CO, while the absorption lines of CO and OCO were being scanned. Continuous measurements of the three isotopologues of 4.7% CO samples over 103 min under free running and frequency locking conditions were performed. The measurement accuracy and precision of the three isotopologues achieved under the frequency locking condition were at least 3 times and 1.3 times better than those obtained under the free running condition, respectively. The Allan variance plot of the developed laser-locked HWG gas sensor shows a detection limit of 0.72‰ for both δC and δO under the frequency locking condition with a long stability time of 766 s. This study demonstrated the high potential of a novel human breath diagnostic sensor for medical diagnostic with high accuracy, precision, and sensitivity and without frequently repeated calibration.
一种基于锁频激光的空心波导（HWG）气体传感器，利用 2.73μm 分布反馈激光器的波长调制光谱技术，实现了对三种同位素（CO、CO 和 OCO）的同时测量。在位于二次谐波（2）信号峰值处的采样点处使用一次谐波（1）信号作为锁定点，将激光频率锁定到 CO 的跃迁中心，同时扫描 CO 和 OCO 的吸收线。在自由运行和频率锁定条件下，对 4.7% CO 样品进行了 103 分钟的连续测量。与自由运行条件相比，在频率锁定条件下，三种同位素的测量精度和精度至少提高了 3 倍和 1.3 倍。所开发的激光锁频 HWG 气体传感器的 Allan 方差图显示，在频率锁定条件下，δC 和 δO 的检测限分别为 0.72‰，具有长达 766s 的长稳定时间。本研究表明，这种新型的人体呼吸诊断传感器具有高精度、高灵敏度和无需频繁重复校准的特点，在医疗诊断方面具有很大的潜力。
