基于光频梳傅里叶变换红外光谱的3.5μm附近甲醛分子宽带光谱测量  

Broadband Spectral Measurement of Formaldehyde Molecules near 3.5μm Based on Optical Frequency Comb Fourier Transform Infrared Spectroscopy

作　　者：李双双 胡长进 程飞虎 赵卫雄[1] 方波[1] 陈杨 杨娜娜 韦娜娜 张为俊[1,3] 邓伦华 Li Shuangshuang;Hu Changjin;Cheng Feihu;Zhao Weixiong;Fang Bo;Chen Yang;Yang Nana;Wei Nana;Zhang Weijun;Deng Lunhua(Anhui Institute of Optics and Fine Mechanics,Hefei Institute of Physical Science,Chinese Academy of Sciences,Hefei 230031,Anhui,China;Science Island Branch,Graduate School,University of Science and Technology of China,Hefei 230026,Anhui,China;School of Environmental Science and Optoelectronics Technology,University of Science and Technology of China,Hefei 230026,Anhui,China;State Key Laboratory of Precision Spectroscopy,East China Normal University,Shanghai 200062,China)

机构地区：[1]中国科学院合肥物质科学研究院安徽光学精密机械研究所,安徽合肥230031 [2]中国科学技术大学研究生院科学岛分院,安徽合肥230026 [3]中国科学技术大学环境科学与光电技术学院,安徽合肥230026 [4]华东师范大学精密光谱国家重点实验室,上海200062

出　　处：《光学学报》2024年第18期428-437,共10页Acta Optica Sinica

基　　金：国家自然科学基金(U21A2028);国家重点研发计划(2022YFC3701101,2022YFC370030401,2022YFC3701104);中国科学院青年创新促进会(Y202089);合肥研究院院长基金(YZJJ202101,BJPY2023A02)。

摘　　要：甲醛(HCHO)是对流层中含量最多的一种醛类,也是室内环境的主要污染物,获得高质量的甲醛光谱对大气科学、室内环境监测具有重要意义。基于此,本文搭建了一套频率梳傅里叶变换红外(FC-FTIR)光谱装置,利用Herriott光学多通池在光学基长仅为1.2 m的条件下获得60 m的吸收光程,最终在室温、低压条件下获得甲醛在3.5μm附近的中红外宽带光谱,谱线的波数精度优于150 MHz。通过多谱线拟合甲醛光谱得到该仪器的探测限为3×10^(-8)cm^(-1)Hz^(-1/2),对应于414×10^(-9)的探测灵敏度。根据实测谱图反演了吸收池内甲醛的体积分数,得到其平均体积分数为3.5×10^(-6),体积分数不确定度为9%~11%。为了体现宽谱测量的优势,还测量了在大量水存在时甲醛的吸收光谱,并确定其分子的体积分数。本装置不仅可以在宽光谱范围内同时获得多个物质的谱图,而且耗时较短,8次测量平均的情况下在35 s的响应时间内即可获得完整的吸收谱图。相较于传统的傅里叶变换红外(FTIR)光谱,中红外FC-FTIR光谱在灵敏度及分辨率相同的条件下,具有采集时间短的显著优势,有望在甲醛等分子的红外光谱测量中发挥重要作用。Objective Formaldehyde is the most abundant aldehyde in the troposphere and a primary indoor pollutant,classified as a human carcinogen.High-sensitivity on-line measurement of formaldehyde is critical for monitoring atmospheric environments and indoor pollution.High-resolution and accurate formaldehyde spectrum are essential for developing high-sensitivity detection instruments and improving spectral inversion accuracy.Therefore,it is of great significance to obtain a high-quality formaldehyde spectrum for formaldehyde research.Fourier transform infrared(FTIR)spectroscopy is a commonly used infrared spectral technique.However,the traditional FTIR spectrometer with an incoherent thermal light source suffers from low sensitivity and requires long averaging time to improve sensitivity.The optical frequency comb is essentially a pulsed laser with the advantages of wide spectrum,high brightness,and good collimation.It can replace the thermal light source in traditional FTIR spectrometer and improve the detection sensitivity by combining a multi-pass cell or an optical resonant cavity.Therefore,we built a Fourier transform spectrometer based on an optical frequency comb to measure the broadband spectrum of formaldehyde and have a quantitative analysis,including measurements in the presence of water interference.Methods Leveraging the advantages of the optical frequency comb and the FTIR in detecting wide-range molecular absorption spectra,an FC-FTIR spectrometer is built to measure the formaldehyde spectrum near 3.5μm.The comb source used is FC1500-250-WG and mid-IR optical frequency comb,generating an infrared laser with a center wavelength of 3200 nm by difference frequency conversion.The laser is collimated into the Herriott-type optical multi-pass cell.The optical base length of the cell is only 1.2 m,and an effective absorption path of 60 m can be obtained after multiple reflections.The comb beam exiting the cell is then focused into the FTIR spectrometer for formaldehyde spectrum detection.Results and Discussion

关 键 词：中红外频率梳 傅里叶变换红外光谱法 甲醛 光学多通池 宽谱 

分 类 号：O433[机械工程—光学工程]