Dong Lei, Yu Yajun, Li Chunguang, So Stephen, Tittel Frank K
Opt Express. 2015 Jul 27;23(15):19821-30. doi: 10.1364/OE.23.019821.
A ppb-level formaldehyde (H2CO) sensor was developed using a thermoelectrically cooled (TEC), continuous-wave (CW) room temperature interband cascade laser (ICL) emitting at 3.59 μm and a miniature dense pattern multipass gas cell with >50 m optical path length. Performance of the sensor was investigated with two measurement schemes: direct absorption (DAS) and wavelength modulation spectroscopy (WMS). With an integration time of less than 1.5 second, a detection limit of ~3 ppbv for H2CO measurement with precision of 1.25 ppbv for DAS and 0.58 ppbv for WMS, respectively, was achieved without zero air based background subtraction. An Allan-Werle variance analysis indicated that the precisions can be further improved to 0.26 ppbv @ 300s for DAS and 69 pptv @ 90 s for WMS, respectively. A side-by-side comparison between two measurement schemes is also discussed in detail.
利用一个热电冷却（TEC）、连续波（CW）、室温下发射波长为3.59μm的带间级联激光器（ICL）以及一个光程长度大于50m的微型密集图案多程气室，开发了一种ppb级甲醛（H2CO）传感器。采用直接吸收（DAS）和波长调制光谱（WMS）两种测量方案对该传感器的性能进行了研究。在积分时间小于1.5秒的情况下，在不进行基于零气背景扣除的情况下，实现了H2CO测量的检测限约为3 ppbv，DAS的精度为1.25 ppbv，WMS的精度为0.58 ppbv。Allan-Werle方差分析表明，DAS的精度在300秒时可进一步提高到0.26 ppbv，WMS在90秒时可提高到69 pptv。还详细讨论了两种测量方案的并排比较。
