A compact multi-gas sensor has been developed for simultaneous detection of atmospheric carbon monoxide (CO), nitrous oxide (N₂O), and methane (CH₄). Instead of the traditional time-division multiplexing detection technique, two lasers having center emission wavelengths of 1.653 μm (near-infrared (NIR) diode feedback (DFB) laser diode) and 4.56 μm (mid-infrared (MIR) quantum cascade laser) were simultaneously coupled to a multipass cell using a dichroic mirror, which significantly decreased the complexity of the measurement and increased the temporal resolution of the spectrometer. Wavelength modulation spectroscopy (WMS) with the second-harmonic detection technique (WMS-2f) was used to improve the detection sensitivity. A LabVIEW-based digital lock-in amplifier (DLIA) algorithm and system control unit was developed to make the system more compact and flexible. Allan deviation analysis indicates that detection limits of 6.36 ppb by volume for CO, 4.9 ppb by volume for N₂O, and 23.6 ppb by volume for CH₄ are obtained at 1 s averaging time, and the sensitivity can be improved to 0.44 ppb for CO, 0.41 ppb for N₂O, and 2 ppb for CH₄ at an optimal averaging time of 900 s. Two-day real-time measurement in ambient air was performed to demonstrate the long-term stability of the sensor system.

中文翻译：

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使用NIR和MIR激光混合气体传感系统同时检测多个大气成分

已开发出紧凑的多气体传感器，用于同时检测大气中的一氧化碳（CO），一氧化二氮（N ₂ O）和甲烷（CH ₄）。代替传统的时分多路复用检测技术，使用了两个中心发射波长为1.653μm的激光器（近红外（NIR）二极管反馈（DFB）激光二极管）和4.56μm（中红外（MIR）量子级联激光器）同时使用二向色镜将其同时耦合至多通道单元，从而大大降低了测量的复杂性并提高了光谱仪的时间分辨率。使用具有二次谐波检测技术（WMS-2f）的波长调制光谱（WMS）来提高检测灵敏度。开发了基于LabVIEW的数字锁定放大器（DLIA）算法和系统控制单元，以使系统更加紧凑和灵活。艾伦偏差分析表明，CO的检测限为6.36 ppb，N的检测限为4.9 ppb₂ O，和23.6 ppb的体积为CH ₄在1秒平均时间获得的，并且灵敏度可以被提高到0.44 ppb的对CO，0.41 ppb的对于N ₂ O，和2 ppb的用于CH ₄在一个最佳的平均时间900秒 在环境空气中进行了为期两天的实时测量，以证明传感器系统的长期稳定性。