Ma Yufei, Lewicki Rafał, Razeghi Manijeh, Tittel Frank K
Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, USA.
Opt Express. 2013 Jan 14;21(1):1008-19. doi: 10.1364/OE.21.001008.
An ultra-sensitive and selective quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor platform was demonstrated for detection of carbon monoxide (CO) and nitrous oxide (N2O). This sensor used a state-of-the art 4.61 μm high power, continuous wave (CW), distributed feedback quantum cascade laser (DFB-QCL) operating at 10°C as the excitation source. For the R(6) CO absorption line, located at 2169.2 cm(-1), a minimum detection limit (MDL) of 1.5 parts per billion by volume (ppbv) at atmospheric pressure was achieved with a 1 sec acquisition time and the addition of 2.6% water vapor concentration in the analyzed gas mixture. For the N2O detection, a MDL of 23 ppbv was obtained at an optimum gas pressure of 100 Torr and with the same water vapor content of 2.6%. In both cases the presence of water vapor increases the detected CO and N2O QEPAS signal levels as a result of enhancing the vibrational-translational relaxation rate of both target gases. Allan deviation analyses were performed to investigate the long term performance of the CO and N2O QEPAS sensor systems. For the optimum data acquisition time of 500 sec a MDL of 340 pptv and 4 ppbv was obtained for CO and N2O detection, respectively. To demonstrate reliable and robust operation of the QEPAS sensor a continuous monitoring of atmospheric CO and N2O concentration levels for a period of 5 hours were performed.
展示了一种用于检测一氧化碳（CO）和一氧化二氮（N₂O）的超灵敏且选择性的石英增强光声光谱（QEPAS）传感器平台。该传感器使用一台工作在10°C的最先进的4.61μm高功率连续波（CW）分布反馈量子级联激光器（DFB-QCL）作为激发源。对于位于2169.2 cm⁻¹处的R(6) CO吸收线，在大气压力下，通过1秒的采集时间以及在分析气体混合物中添加2.6%的水蒸气浓度，实现了1.5体积十亿分之一（ppbv）的最低检测限（MDL）。对于N₂O检测，在100 Torr的最佳气压和相同2.6%的水蒸气含量下，获得了23 ppbv的MDL。在这两种情况下，水蒸气的存在由于提高了两种目标气体的振动 - 平动弛豫速率，从而增加了检测到的CO和N₂O的QEPAS信号水平。进行了阿伦偏差分析以研究CO和N₂O QEPAS传感器系统的长期性能。对于500秒的最佳数据采集时间，CO和N₂O检测分别获得了340 pptv和4 ppbv的MDL。为了证明QEPAS传感器可靠且稳健的运行，对大气中的CO和N₂O浓度水平进行了为期5小时的连续监测。
