基于空芯光纤光热光谱技术的高灵敏度CO_(2)检测

Carbon Dioxide Detection with High Sensitivity Based on Photo-Thermal Spectroscopy in Hollow-Core Optical Fiber

研究了基于空芯光纤光热光谱技术的2μm波段CO2高灵敏度检测关键技术,采用基于反谐振空芯光纤的低锐度法布里-珀罗干涉仪实现光热相位解调。对于波长为2004.02 nm的CO2 R(18)吸收线,在180 mW的泵浦功率以及1 s的积分时间下,噪声等效体积分数约4.7×10-8。为提高系统测量的稳定性,对光纤端面镀膜以抑制泵浦光的干涉效应,同时将探测器波长锁定到干涉仪的工作点上。1 h内,体积分数为10-5的CO2标准气体对应的信号波动约4.7%。噪声分析表明,探测光源的相位噪声和强度噪声是当前系统的主要噪声来源。

The key techniques for the high-sensitivity detection of CO2 in the 2μm band are studied based on photo-thermal spectroscopy in a hollow-core optical fiber,and a low-sharpness Fabry-Perot interferometer based on anti-resonance hollow-core optical fiber is adopted to demodulate the photo-thermal phase.For the R(18)absorption line of CO2 at 2004.02 nm,the noise equivalent volume fraction is about 4.7×10-8 with a pump power of 180 mW and integration time of 1 s.To improve the stability of the detection system,we suppress the intra-cavity interference of pump light by applying the anti-reflection coating to the fiber end face and lock the probe wavelength to the quadrature point of the interferometer.Within 1 h,the signal fluctuation corresponding to CO2 standard gas with volume fraction of 10-5 is about 4.7%.Noise analysis shows that the noise mainly comes from the phase noise and intensity noise of the probe laser in the current detection system.