关键词: 痕量气体检测/
石英增强光声光谱/
光纤倏逝波
English Abstract
Fiber evanescent wave quartz-enhanced photoacoustic spectroscopy
He Ying,Ma Yu-Fei,
Tong Yao,
Peng Zhen-Fang,
Yu Xin
1.National Key Laboratory of Science and Technology on Tunable Laser, Harbin Institute of Technology, Harbin 150001, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant No. 61505041), the Natural Science Foundation of Heilongjiang Province of China (Grant No. F2015011), the Special Financial Grant from the China Postdoctoral Science Foundation (Grant No. 2015T80350), the General Financial Grant from the China Postdoctoral Science Foundation (Grant No. 2014M560262), the Postdoctoral Fund of Heilongjiang Province, China (Grant Nos. LBH-Z14074, LBH-TZ0507), the Fundamental Research Funds for the Central Universities, the Application Technology Research and Development Projects of Harbin, China (Grant No. 2016RAQXJ140), and the National Key Scientific Instrument and Equipment Development Projects of China (Grant No. 2012YQ040164).Received Date:21 August 2017
Accepted Date:22 September 2017
Published Online:20 January 2019
Abstract:In a conventional system of quartz-enhanced photoacoustic spectroscopy (QEPAS), the size of block-like optical collimation focusing lens group is difficult to reduce, and the structural stability is poor, which makes it hard to adapt itself to some special conditions, such as narrow space and vibrating circumstance. Based on this situation, in this research the fiber evanescent wave technique is combined with QEPAS. Therefore, trace gas detection for acetylene (C2H2) based on an all-fiber structural QEPAS system is developed. To obtain the characteristics of fiber evanescent wave, the optical distribution of micro structural fiber is simulated and the evanescent wave power ratio is calculated based on the COMSOL Multiphysics software. In order to increase the QEPAS 2f signal amplitude, the optical path between fiber taper and quartz tuning fork (QTF) and the laser wavelength modulation depth are optimized. In addition, two kinds of QTFs with different resonant frequencies are optimized. Finally, a QTF with a lower resonant frequency of 30.720 kHz is adopted as the acoustic wave transducer, and a minimum detection limit (MDL) of 6.2510-4 (volume fraction) is obtained with a laser wavelength modulation depth of 0.24 cm-1. To investigate the evanescent wave power of micro structural fiber, the fiber taper diameter is measured by a scanning electron microscope. Subsequently, by combining the diameter of fiber taper with the theoretical calculation results, we determine an evanescent wave power of 455.9 W, and the normalization of noise equivalent absorption (NNEA) which indicates the sensor sensitivity is 4.1810-7 cm-1WHz-1/2.
Keywords: trace gas detection/
quartz-enhanced photoacoustic spectroscopy/
fiber evanescent wave
