Trace gas measurements using optically resonant cavities and quantum cascade lasers operating at room temperature
Trace gas measurements using optically resonant cavities and quantum cascade lasers operating at room temperature
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使用光学谐振腔和室温下运行的量子级联激光器进行痕量气体测量
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
J. Röpcke
中科院分区：
文献类型：
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作者：
S. Welzel;G. Lombardi;P. Davies;R. Engeln;D. Schram;J. Röpcke
要在中红外分子指纹区域实现微量气体检测所需的高灵敏度，通常需要较长的吸收路径长度。此外，对于更广泛的应用，特别是现场测量，紧凑型和无低温光谱仪绝对是首选。传统的线性吸收光谱采用多通池来获得高灵敏度，另一种方法是将高精细腔与热电(TE)冷却量子级联激光器(QCL)和探测器相结合。我们研究了一个完全TE制冷系统的灵敏度极限，该系统配备了一个长为∼0.5 m的腔长为0.3 L的小样品体积。在这个光谱仪的腔增强吸收光谱中，采用波长为7.66 μm的连续波QCL，得到了1080m的光程长度和2×10−7 cm−1 HZ−1/2的噪声当量吸收。对于N2O和N2O，当积分时间为20 S时，检测下限为6×10 8 分子/cm~3。
Achieving the high sensitivity necessary for trace gas detection in the midinfrared molecular fingerprint region generally requires long absorption path lengths. In addition, for wider application, especially for field measurements, compact and cryogen free spectrometers are definitely preferable. An alternative approach to conventional linear absorption spectroscopy employing multiple pass cells for achieving high sensitivity is to combine a high finesse cavity with thermoelectrically (TE) cooled quantum cascade lasers (QCLs) and detectors. We have investigated the sensitivity limits of an entirely TE cooled system equipped with an ∼0.5 m long cavity having a small sample volume of 0.3 l. With this spectrometer cavity enhanced absorption spectroscopy employing a continuous wave QCL emitting at 7.66 μm yielded path lengths of 1080 m and a noise equivalent absorption of 2×10−7 cm−1 Hz−1/2. The molecular concentration detection limit with a 20 s integration time was found to be 6×108 molecules/cm3 for N2O a...