关键词: 激光光谱/
量子级联激光器/
大气多组分/
痕量探测
English Abstract
Detection of atmospheric multi-component based on a single quantum cascade laser
Zhou Chao,Zhang Lei,
Li Jin-Song
1.Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education, Anhui University, Hefei 230601, China
Fund Project:Project supported by the National Key Research and Development Program of China (Grant No. 2016YFC0302202), the National Natural Science Foundation of China (Grant Nos. 61675005, 61440010), the Natural Science Fund of Anhui Province, China (Grant No. 1508085MF118), the Key Science and Technology Development Program of Anhui Province, China (Grant No. 1501041136), the Anhui Scholarship Council of China (Grant No. J05015143), the Anhui University Personnel Recruiting Project of Academic and Technical Leaders, China (Grant No. 10117700014), and the Undergraduate Research Program, China (Grant Nos. J10118515790, J10118520289).Received Date:21 December 2016
Accepted Date:17 January 2017
Published Online:05 May 2017
Abstract:Quantum cascade lasers (QCLs) are relatively new sources of mid-infrared radiation (between 2.5 m and 25 m), and are very well suited to the application of in-field trace gas sensing, mainly due to their superiority of being robust, compact, wavelength-versatile, narrow line width and low power consumption. All these advantages make the laser absorption spectroscopy based on QCL light sources become one of the most popular technologies for the quantitative chemical detection in a variety of fields including atmospheric environmental monitoring, chemical analysis, industrial process control, medical diagnostics, security or bio-medical studies, etc.In the present work, a highly sensitive mid-infrared gas sensor employing a single continuous-wave distributed feedback QCL and an astigmatic multi-path optical absorption cell is demonstrated for the simultaneous measurement of atmospheric carbon monoxide (CO), nitrous oxide (N2O) and water vapor (H2O). By combining with an adaptive Savitzky-Golay (S-G) filter signal processing algorithm, the detection sensitivity and spectral resolution of the QCL sensor system are significantly improved. Compared with the traditional wavelet transform based signal de-noising technique, the developed adaptive S-G smoothing filter shows obvious advantages in terms of computational efficiency and selection of the optimal filter parameters, namely only two filter parameters (the width of the smoothing window and the degree of the smoothing polynomial) need to be considered. Currently, the QCL sensor system is estimated for the long term measurement of ambient air in laboratory environment. The results show that measurement precisions of 8.20 ppb (1 ppb=10-9) for CO, 7.90 ppb for N2O, and 64.00 ppm (1 ppm=10-6) for H2O at 1 s time resolution and 1 atmospheric pressure (atm) are obtained by using the quadratic differential detection scheme, which can be further improved to 1.25 ppb (for CO), 1.15 ppb (for N2O) and 35.77 ppm (for H2O) by increasing average time up to 85 s, respectively. On the whole, the QCL sensor system has significant features of portability and low-cost, moreover, it can be easily modified for the real-time analysis of other gas molecules through the choosing of corresponding QCL light sources. The QCL gas sensor can be widely used in the field of atmospheric chemistry and other applications. Future work will focus on H2O induced broadening coefficients for CO and N2O transitions near 4.57 m, which will be updated for the developed multi-species QCL sensor system, thus resolving the influence of water vapor broadening effect and achieving the measurement of gas concentration in a high humid environment with sub-percent precision.
Keywords: laser spectroscopy/
quantum cascade laser/
multi atmospheric species/
trace detection
