论文类型：期刊论文
论文编号：106906
第一作者：邓柏涛
通讯作者：司马朝坦
合写作者：鲁平,刘德明
发表刊物：Optics and Lasers in Engineering
收录刊物：SCI、EI
所属单位：Elsevier
学科门类：工学
一级学科：光学工程
文献类型：J
卷号：151
ISSN号：0143-8166
关键字：Feedback monitoring; Half-wave scanning; Low sampling rate; Nonlinear scanning; TDLAS
DOI码：10.1016/j.optlaseng.2021.106906
发表时间：2021-12-13
影响因子：4.836
摘要：Tunable diode laser absorption spectroscopy (TDLAS) for trace gas sensing has been investigated widely. Conventional wavelength-modulation spectroscopy (WMS) in TDLAS usually involves linear triangle patterns for tunable laser scanning. Here, a novel modified laser scanning technique is proposed and experimentally demonstrated in the WMS-based TDLAS gas sensor. The half-wave scan is primarily introduced to drive the laser diode to cover 1/2 range of the Lorentz-like gas absorption line. By monitoring waveform derivation of second harmonics, real-time status of the laser output could be exhibited and the output wavelength constancy can be controlled. It is also verified that second harmonics feature basically linearly with wavelength drifts, allowing the in-situ regulation of laser wavelength stability. Moreover, the nonlinear half-wave scan is introduced and designs a nonlinear function across the scanning pattern. It enlarges the temporal window around strong absorption and consequently acquires additional valuable waveform data. With the limited sampling rate for TDLAS signal processing, by using the nonlinear half-wave scan, second harmonics fluctuate merely 1/3 of that in the conventional WMS-2f linear scan. The proposed modified laser scanning technique is employed in a methane sensor, realizing about 3 ppm minimum detection limit and 9.6 ppm measurement accuracy. This technique is beneficial and universal for real-time monitoring and in-situ control of laser sources and improvement in accuracy and stability for current WMS-based TDLAS gas detection.