基于宽带可调谐、窄线宽掺铥光纤激光器的2μm波段水的超光谱吸收测量  

Hyperspectral absorption of water around 2 μm based on a boradband tunable, narrow linewidth Tm-doped fiber laser

作　　者：陶蒙蒙 王亚民[2] 吴昊龙 李国华 王晟[2] 陶波[2] 叶景峰[2] 冯国斌[2] 叶锡生[1] 陈卫标 Tao Meng-Meng;Wang Ya-Min;Wu Hao-Long;Li Guo-Hua;Wang Sheng;Tao Bo;Ye Jing-Feng;Feng Guo-Bin;Ye Xi-Sheng;Chen Wei-Biao(Wang Zhijiang Laser Innovation Center,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;State Key Laboratory of Laser Interaction with Matter,Northwest Institute of Nuclear Technology,Xi’an 710024,China)

机构地区：[1]中国科学院上海光学与精密机械研究所,王之江激光创新中心,上海201800 [2]西北核技术研究所,激光与物质相互作用国家重点实验室,西安710024

出　　处：《物理学报》2022年第11期178-185,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:62105268,91841303,52106222);激光与物质相互作用国家重点实验室基金(批准号:SKLLIM2110)资助的课题。

摘　　要：1.8—2.0μm波段包含大量水的吸收谱线,且吸收强度高于传统的1.3—1.5μm波段,在水的吸收光谱测量中具有很大的应用潜力.超光谱吸收测量技术可以利用宽带范围内的大量吸收谱线来实现物理参数的反演,与传统的单/双谱线的可调谐二极管吸收光谱技术相比具有更好的稳定性、准确性和更宽的使用范围.宽带调谐的窄线宽激光光源是实现超光谱吸收测量的关键器件.利用可调谐法布里-珀罗(FP)腔和光纤可饱和吸收体,搭建了宽带调谐的窄线宽2μm光纤激光器.利用掺铥光纤的再吸收特性,通过合理设计增益光纤长度,得到了在1910—1970 nm约60 nm的光谱范围内连续可调的激光输出,且激光器静态线宽小于0.1 nm,能够满足水的超光谱吸收测量实验的要求.利用该激光器分别对空气和酒精火焰中水在2μm波段的宽带吸收光谱进行了测量.在常温空气中,该光源可以在1910—1965 nm的光谱范围内有效分辨40余条水的吸收谱线;在酒精火焰中,该光源可以在1950—1970 nm的光谱范围内有效分辨近50条水的吸收谱线.通过与HITRAN2016数据库的比对反演得到激光器在动态扫描过程中的线宽约为0.06 nm,与静态测试结果相近;反演得到的空气温度约为298 K,空气中水的摩尔分数约为2%,与温湿度计测量结果一致;反演得到的酒精火焰温度约为1220 K,与热电偶测量结果较为接近.The 1.8-2.0μm waveband contains abundant absorption lines of water,which are much stronger than those in the traditional 1.3-1.5μm waveband,exhibiting huge potentials for absorption spectrum applications of water.In the hyperspectral absorption spectrum,physical parameters of the target molecule can be derived from lots of absorption lines within a broadband scanning range,achieving the results more robust,accurate and versatile than the results from the conventional tunable diode laser absorption spectrum in which only one or two absorption lines are used.The key to hyperspectral absorption is the development of broadband tunable,narrow linewidth laser sources emitting in the wavelength range of interest.With a tunable fiber FP filter and a fiber saturable absorber,a Tm-doped fiber laser is established,featuring broadband tenability and narrow linewidth.Taking advantage of the re-absorption characteristics of Tm-doped silica fibers,a wavelength tuning range covering 60 nm from 1910-1970 nm is obtained through the appropriately designing of the active fiber length.The measured laser linewidth at steady state is smaller than 0.1 nm,which is suitable for water absorption spectrum.Hyperspectral absorption measurements of water in air and alcohol flame are conducted.In room-temperature air,more than 40 absorption lines are recognized within a tuning range of 1910-1965 nm,while,in alcohol flame,the number of detected lines reaches about 50.Comparison with the HITRAN2016 database gives a laser linewidth of about 0.06 nm which is very close to the static linewidth measured by an OSA.The temperature of the air is derived to be 298 K with a water mole fraction of about 2%,which is consistent with the measurement of the hygrothermograph.And the calculation indicates an alcohol flame temperature of about 1220 K,which is very close to the measurement result of the thermocouple.

关 键 词：超光谱吸收 可调谐二极管激光吸收光谱 光纤可饱和吸收体 掺铥光纤激光器 

分 类 号：TN248[电子电信—物理电子学] TN253