可调谐二极管激光吸收光谱法监测环境空气中甲烷的浓度变化

可调谐二极管激光吸收光谱（TDLAS）技术是利用二极管激光器波长调谐特性，获得被测气体在特征吸收光谱范围内的吸收光谱，从而对污染气体进行定性或定量分析。通过该方法对环境空气中甲烷（CH4）的含量进行了长时间的监测。以室温下工作的近红外可调谐半导体激光器作为光源；使用多次反射池增加吸收光程来提高检测灵敏度；并且使用了二次谐波检测技术进一步降低了检测限，使检测限低于0.087mg／m^3，满足了对环境空气中甲烷进行监测的需要。

Tunable Diode Laser Absorption Spectrometer Monitors the Ambient Methane with High Sensitivity

Tunable diode laser absorption spectroscopy(TDLAS) technique is a new method to detect trace-gas qualitatively or quantificationally based on the scan characteristic of the diode laser to obtain the absorption spectra in the characteristic absorption region.It needs to combine with a long absorption path in the ambient trace-gas measurements.It has a significant advantage not only in sensitivity but also in rapidity of response.The experimental results of monitoring of methane of the ambient air in a long time with a ground-based portable TDLAS system are described;it works with a room-temperature near infrared tunable diode laser to measure methane in the ambient air,the path length is lengthened by the multiple-reflection cell to lower the detection limit;and the second harmonic detection is used to lower the detection limit farther;the detection limit is below 0.087 mg/m~3,that is enough to the monitoring of ambient methane.