由于工业监控和环境检测的需要, 甲烷气体检测日益得到人们的关注。 研究了基于中红外分布反馈量子级联激光器（DFB-QCL）的光声光谱技术, 并应用于痕量甲烷的检测。 自主研发的DFB-QCL室温工作时的激射波长在7.6 μm附近, 覆盖了甲烷的特征吸收谱线1 316.83 cm-1。 待测甲烷气体充入亥姆霍兹光声谐振腔中, DFB-QCL的工作频率为234 Hz、 室温脉冲工作时峰值功率为80 mW。 中红外光经过甲烷吸收后, 产生的声波信号经麦克风检测, 由锁相放大器对信号进行采集并输入计算机进行处理。 按信噪比为1计算, 得到甲烷的探测极限为189 nmol·mol-1。

There have been considerable interests in methane detection based on infrared absorption spectroscopy for industrial and environment monitoring. The authors report on the realization of photoacoustic detection of methane (CH4) using mid-infrared distributed-feedback quantum cascade laser (DFB-QCL). The absorption line at 1 316.83 cm-1 was selected for CH4 detection, which can be reached by the self-manufactured DFB-QCL source operating in pulsed mode near 7.6 μm at room-temperature. The CH4 gas is filled to a Helmholtz resonant photoacoustic cell, which was equipped with a commercial electret microphone. The DFB-QCL was operated at 234 Hz with an 80 mW optical peak power. A detection limit of 189 parts per billion in volume was derived when the signal-to-noise ratio equaled 1.