光学学报, 2015, 35 (9): 0930002, 网络出版: 2015-09-01
高灵敏度快速扫描光腔衰荡光谱方法探测大气CH4含量 下载: 611次
High-Sensitivity Rapidly Swept Cavity Ringdown Spectroscopy for Monitoring Ambient CH4
光谱学 高灵敏度光学探测 光腔衰荡光谱 空气污染监测 激光传感器 甲烷 spectroscopy high-sensitivity optical detection cavity ringdown spectroscopy air pollution monitoring laser sensors methane
摘要
搭建了基于近红外连续激光器的高灵敏度快速扫描光腔衰荡光谱仪(SC-CRDS)。通过压电陶瓷(PZT)快速扫描腔长,并用跟踪电路使腔长自动跟踪激光波长变化,实现衰荡光谱的快速测量。利用CH4在1653.73 nm (6046.95 cm-1)附近的光谱吸收峰,用该装置对CH4气体含量进行测量。通过测量多个光谱点确定吸收线中心吸收峰值和激光波长,并反馈补偿激光中心波长使其稳定在吸收线,成功解决了由于激光器波长/频率严重漂移导致的不能持续准确测量问题。利用标准浓度的CH4样品校准其1653.73 nm 吸收峰谱线强度。该光腔衰荡光谱仪装置结构简单,性能稳定,CH4浓度检测限达到1.0×10-9,可用于长时间监测室外空气中的CH4浓度。
Abstract
A rapidly-swept high-sensitivity cavity ringdown spectrometer (SC-CRDS) has been developed based on near-infrared continuous-wave diode lasers. By rapid sweeping/dithering of the ringdown cavity length via a piezo-electric transducer (PZT) , in combination with an automatic cavity length tracking circuit to follow laser wavelength changes, fast CRDS measurements are achieved. This system is applied for measurement of CH4 concentration by detecting its spectroscopic absorption peak around 1653.73 nm (6046.95 cm- 1). By measuring multiple spectral points around the absorption peak, both the peak absorption value and corresponding laser wavelength are determined. A feedback control to the laser wavelength helps to stabilize its center wavelength to the absorption peak. Therefore, it successfully solves the problem of strong wavelength drift of the laser in free operation. The line strength of the CH4 1653.73 nm absorption feature is calibrated by measuring CH4 premixture samples with reference concentrations. This simple CRDS system shows stable and reliable performance as well as a CH4 concentration detection limit of 1.0×10-9; and it can be applied to monitor CH4 in ambient air over a long time.
孙丽琴, 陈兵, 阚瑞峰, 李明星, 姚路, 魏敏, 何亚柏. 高灵敏度快速扫描光腔衰荡光谱方法探测大气CH4含量[J]. 光学学报, 2015, 35(9): 0930002. Sun Liqin, Chen Bing, Kan Ruifeng, Li Mingxing, Yao Lu, Wei Min, He Yabai. High-Sensitivity Rapidly Swept Cavity Ringdown Spectroscopy for Monitoring Ambient CH4[J]. Acta Optica Sinica, 2015, 35(9): 0930002.