中红外波长调制离轴积分腔输出光谱技术应用于OH自由基高灵敏度探测研究  

Wavelength Modulation Off-axis Integrated Cavity Output Spectroscopy for High-sensitivity Detection of OH Radicals in Mid-infrared

作　　者：杨娜娜 方波[1] 王春晖 周昊 韦娜娜[1] 赵卫雄 张为俊[1,3] YANG Nana;FANG Bo;WANG Chunhui;ZHOU Hao;WEI Nana;ZHAO Weixiong;ZHANG Weijun(Anhui Institute of Optics and Fine Mechanics,HFIPS,Chinese Academy of Sciences,Hefei 230031,China;University of Science and Technology of China,Hefei 230026,China;School of Environmental Science and Optoelectronic Technology,University of Science and Technology of China,Hefei 230026,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,合肥230031 [2]中国科学技术大学,合肥230026 [3]中国科学技术大学环境科学与光电技术学院,合肥230026

出　　处：《光子学报》2023年第3期278-286,共9页Acta Photonica Sinica

基　　金：国家自然科学基金(Nos.42022051,41627810);中国科学院青年创新促进会(No.Y202089),中国科学院合肥物质科学研究院院长基金(Nos.YZJJ202101,BJPY2019B02)。

摘　　要：将波长调制技术与离轴积分腔技术相结合,建立了波长调制离轴积分腔输出光谱实验装置,增加吸收光程,避免低频的1/f噪声和与波长无关的背景功率的影响,将其应用于OH自由基探测研究。探测激光器选择2.8μm中红外室温型连续波分布反馈式二极管激光器,OH自由基选择3568.52 cm^(-1)处Q(1.5e)跃迁谱线开展光谱探测,在512 m有效吸收光程和100 s采样时间下,实现了OH自由基1.2×10^(8)molecule/cm3的探测极限。实验研究发现,在弱透过光强下,激光器放大的自发辐射对吸收系数测量影响大,本实验装置下造成了约70倍的吸收低估,需要有效避免。The hydroxyl(OH)free radical is one of the most important oxidants and is at the origin of the majority of chemical transformations in the troposphere.It plays a key role in the formation of ozone and secondary organic aerosols.Accurate and quantitative measurements of OH radical is of great significance to atmospheric chemistry research and air quality control.However,due to the low concentrations in the atmosphere(~10~6 molecule/cm^(3)),high reactivity,and very short lifetime(<1 s),current techniques that can be successfully employed for tropospheric OH measurement are extremely limited.Therefore,there is a strong driving force for the development of new techniques.Off-axis Integrated Cavity Output Spectroscopy(OA-ICOS)based on Lambert-Beer law can offer an ultra-long optical pathlength on the order of kilometers utilizing a high-finesse optical resonator with a limited optical base length.In addition,the off-axis paths through optical cavity can actively excite higher-order transverse modes and effectively reduce the influence of cavity mode fluctuation.These advantages make it a powerful tool for sensitive measurement of OH radical.We reported the development of a mid-infrared OA-ICOS experimental setup.A room temperature continuous-wave distributed feedback diode laser emitting at 2.8μm was used as the probe laser.The Q(1.5e)transition line of OH radical located at 3568.52 cm-1was selected for detection.The integrated cavity consisted of two 25.4-mm diameter high-reflectivity dielectrically coated plano-concave mirrors(1 m radius of curvature)separated by a distance of 35.8 cm.The measured effective reflectivity of the cavity mirrors was 0.9993,corresponding to the effective optical path of 512 m.In this mid-infrared OA-ICOS system,the amplified spontaneous emission of the distributed feedback laser,which is usually on the order of nanowatts and is a kind of unwanted broadband radiation outside the highly reflective band of the cavity mirrors,directly passed through the cavity without resonating.This amplif

关 键 词：激光吸收光谱 中红外 离轴积分腔 放大的自发辐射 OH自由基 

分 类 号：O433.4[机械工程—光学工程]