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《Acta Optica Sinica》 2017-08
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Off-Axis Integrated Cavity Output Spectroscopy Technique Based on Wavelength Modulation

Wu Tao;Xu Dong;He Xingdao;Lai Rong;Cheng Tao;Jiangxi Engineering Laboratory for Optoelectronic Testing Technology,Nanchang Hangkong University;National Engineering Laboratory for Nondestructive Testing and Optoelectronic Sensing Technology and Application,Nanchang Hangkong University;  
An experimental device of wavelength modulated off-axis integrated cavity output spectroscopy(WM-OAICOS)technique is reported.A distributed feedback(DFB)laser with central wavelength of 1.392μm is chosen as light source.A resonant cavity is composed of two mirrors with reflectivity of 99.8% and 60 cm distance,and the cavity is used as gas absorption cell.The absorption line of CH_4 at 7185.87cm~(-1) is selected to detect CH_4 with different concentrations.The stability time of the system is obtained to be 203 sby optimizing the instrument parameters(pressure,modulation frequency,phase and amplitude)combining with Allan variance.The detection limit of CH_4 is obtained to be 8.7×10~(-7) by selecting the measurement time of 100 s,and the corresponding minimum detectable absorption is 2.2×10~(-6) Hz~(-1/2).Compared with that of off-axis integrated cavity output spectroscopy technique,the sensitivity of WM-OA-ICOS technique increases by 21 times.The second harmonic peak height and the ratio of the peak height of second harmonic to the medium of first harmonic(2f/1f)are used to measure the concentration of CH_4,and the results show that the latter has better stability and higher degree of linearity correlation.
【Fund】: 国家自然科学基金(41265011);; 江西省研究生创新专项资金(YC2015-S330);; 人社部留学人员科技活动项目择优资助项目
【CateGory Index】: O433
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