基于1392nm高灵敏度积分腔的痕量水汽测量  

Measurement of Trace Moisture Based on Integrated Cavity at 1392 nm with High Sensitivity

作　　者：徐冬[1,2] 吴涛[1,2] 何兴道[1,2] 房辉[1,2] 

机构地区：[1]南昌航空大学江西省光电检测技术工程实验室,江西南昌330063 [2]南昌航空大学无损检测与光电传感技术及应用国家地方联合工程实验室,江西南昌330063

出　　处：《激光与光电子学进展》2017年第6期306-315,共10页Laser & Optoelectronics Progress

基　　金：国家自然科学基金(41265011);江西省研究生创新专项资金(YC2015-S330);人社部留学人员科技活动项目择优资助项目

摘　　要：介绍了基于分布式反馈(DFB)激光器作为光源的离轴积分腔吸收光谱装置,并将其应用于高纯氮气(N_2)以及标准甲烷(CH_4)中水汽含量的测量。将中心波长为1392nm的出射光,通过准直器耦合到长度为60cm,由两片高反射率镜片组成的谐振腔内,透过腔的信号经过聚焦后由光电探测器接收。利用CH_4标准气体在不同压强下对腔镜的反射率进行校准。当腔内的压强为1.599kPa时,镜片的反射率可达到0.99843±0.00003。选取H2O在7189.344cm^(-1)和7185.597cm^(-1)处的谱线分别对N_2和CH_4中的水汽进行测量。在200s采集时间内,最佳噪声等效吸收系数分别为1.65×10^(-8) cm^(-1)和3.75×10^(-8)cm^(-1),对应的体积分数探测极限分别为2.28×10^(-6)和4×10^(-6)。采用本波段最强的吸收谱线(7181.155cm^(-1)),探测极限可以分别提高24倍和19倍左右,达到95×10^(-9)和210×10^(-9)。若采用反射率更高的镜片,结合最强的吸收谱线,则该系统水汽体积分数的探测极限可以达到10^(-12)量级。We report an off-axis integrated cavity absorption spectroscopy instrument based on distributed feedback （DFB） laser and applied it for measuring trace moisture in high purity nitrogen gas and standard methane. The light emitting from the laser centered at 1392 nm is directly focused into the cavity formed with two high reflectivity mirrors, separated by a distance of 60 cm. The output signal of the cavity is focused into the photoelectric detector. The mirror reflectivity is calibrated by that of standard methane detected at different pressures. The reflectivity of the cavity mirror is measured to be 0. 99843±0.00003 at 1. 599 kPa. The H2O absorption lines at 7189. 344 cm-1 and 7185. 597 cm-1 are respectively used for measuring trace moisture in high purity nitrogen gas and standard methane. The optimum noise-equivalent absorption coefficients of 1.65 × 10-8 cm-1 and 3.75 × 10-8 cm-1 in 200 s are achieved, respectively, which corresponded to the volume fraction detection limits of 2.28 × 10-6 and 4 ×10-6 . The volume fraction detection limit can be increased by about 24 times and 19 times, respectively, reaching about 95 ×10.9 and 210× 10-9 via the strongest absorption line at 7181. 155 cm-1. The volume fraction detection limit ofthe system can be up to the level of 10-12 if the mirrors with a higher reflectivity and the strongest absorption line are used.

关 键 词：光谱学 痕量检测 吸收光谱 离轴积分吸收 水分含量 

分 类 号：O433[机械工程—光学工程]