摘要
对比了波长调制和腔长调制两种方式实现模式匹配的性能特点,通过测量空腔衰荡时间并进行Allan方差分析,得到两种调制方式的衰荡时间分别为(5.239±0.077)μs和(5.252±0.058)μs,该系统的吸收系数检测限为10^(-10)量级。对于甲烷气体浓度,通过步进式改变入射激光的波长,描绘了甲烷气体的吸收谱线,其检测限可达10^(-9)量级。利用波长调制和腔长调制方式得到环境中甲烷气体的浓度分别为1.868×10^(-6)和1.870×10^(-6)。实验结果表明,虽然波长调制和腔长调制均能实现模式匹配,完成痕量甲烷气体的测量,但是通过对比可知:腔长调制方式具有更高的测量精度和更低的浓度检测限;波长调制方式发挥了可调谐激光器的优势,结构相对简单,无需压电陶瓷等附加的机械结构。因此,在实际应用中可根据需求在测量性能和装置复杂度及成本之间进行取舍。
Objective Continuous-wave cavity ring-down spectroscopy(CW-CRDS)is based on absorption spectroscopy,which can enhance the absorbance of trace gas through an ultralong optical path formed by high reflectivity mirrors to achieve high sensitivity and high precision measurement.The ring-down cavity comprises two high reflectivity mirrors with a distance of 50 cm(reflectivity is 99.99%,radius of curvature is 1 m)and high fineness.The free spectral range(FSR)is the interval between two adjacent modes,and the phase difference is an integral multiple of 2π.According to the characteristics of CW-CRDS,mode matching is crucial to achieve effective detection.The linewidth of a semiconductor laser(3 MHz)is much smaller than that of FSR(300 MHz),and the frequency of the incident light usually falls between two longitudinal modes,so the mode matching cannot occur actively.In this study,to improve the matching efficiency and avoid random matching between incident light and cavity mode,wavelength modulation and cavity length modulation were used to realize resonance between incident light frequency and cavity mode,respectively.Methods In this experiment,the performance characteristics of wavelength modulation and cavity length modulation were introduced and compared.Ideally,there was a matching signal in one acquisition period,so the selection of scanning amplitude depended on the FSR.In wavelength modulated cavity ring-down spectroscopy(CRDS),it was easy to match the cavity mode by scanning the incident light frequency in a small range.According to the measurement results of multiple groups of scanning amplitude(Fig.4,Table 1),15 mV was selected as the best scanning range,so the cavity ring-down time(τ_(0))was more accurate and the standard deviation was smaller.Similarly,in CRDS with cavity length modulation,the piezoelectric ceramics(PZT)changed the cavity length by high-voltage driving,so the longitudinal mode frequency changed and resonated with the incident light frequency and achieved mode matching.The choice of the driv
作者
李哲
张志荣
夏滑
孙鹏帅
余润罄
王华东
吴边
Li Zhe;Zhang Zhirong;Xia Hua;Sun Pengshuai;Yu Runqing;Wang Huadong;Wu Bian(Anhui Provincial Key Laboratory of Photonic Devices and Materials,Anhui Institute of Optics and Fine Mechanics,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei,Anhui 230031,China;University of Science and Technology of China,Hefei,Anhui 230026,China;Key Lab of Environmental Optics&Technology,Anhui Institute of Optics and Fine Mechanics,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei,Anhui 230031,China;Advanced Laser Technology Laboratory of Anhui Province,National University of Defense Technology,Hefei,Anhui 230037,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2022年第4期174-183,共10页
Chinese Journal of Lasers
基金
国家自然科学基金(11874364,41877311,42005107)
国家重点研发计划(2017YFC0805004)
安徽省重点研究与开发计划(201904c03020005)
安徽省科技重大专项(18030901054)。
关键词
光谱学
腔衰荡吸收光谱技术(CRDS)
模式匹配
波长调制
腔长调制
衰荡时间
spectroscopy
cavity ring-down absorption spectroscopy
mode matching
wavelength modulation
cavity length modulation
ring-down time
