一氧化碳是一种无色、 无味、 有毒、 易燃的危险气体, 且低浓度的该气体可以使人中毒、 窒息、 危及生命。 因此研制一种能够检测一氧化碳气体浓度的检测仪意义重大, 尤其在环境复杂(湿度和粉尘浓度都很大)的矿井下。 本文所述的是一种紧凑型检测仪器, 其能够灵敏、 快速、 连续地监测环境空气中痕量一氧化碳气体浓度。 该仪器采用激发波长为48 μm的中红外量子级联激光器(QCL)和红外碲镉汞探测器的最新半导体技术, 结合中红外光程长度为76 m的多次反射herriott吸收气室, 可以在4 s的采样时间内实现40 nmol·mol-1气体检测灵敏度。 同时, 该仪器利用差分吸收光谱检测原理, 设计了双光路双通道空间光学结构, 消除了电调制光源所带来的不稳定性, 有效地提高了仪器浓度检测下限。 实验表明, 该仪器通过所集成的气体浓度反演算法, 能够在无需校准的情况下, 可以用于环境监测中的实地痕量气体测量, 并且操作人员可以通过替换在不同波长下运行的QCL来测量其他气体。

Presented in the present paper is a compact instrument developed for rapid, sensitive and continuous monitoring of trace gases in air, with results shown for carbon monoxide concentration. This instrument takes advantage of recent technology in mid-infrared quantum cascaded laser (QCL) operating at 48 μm and mercury cadmium telluride (HgCdTe) mid-infrared (MIR) detector, combing MIR multipass herriott cell with 76 m absorption path length to obtain low detection sensitivity down to 50 nmol·mol-1 level in 4 s acquisition time. Meanwhile, in order to eliminate the instability induced by electrically modulated light source and effectively improve detection limit of the instrument, an optical structure with dual channel path was designed which is based on differential optical absorption spectroscopy method. The experimental results show that the instrument integrated with gas concentration inversion algorithm can be applied to in-situ measurements of trace gases without calibration. Additionally, operator could substitute a QCL operating at a different wavelength to measure other gases.