Open-path sensor based on QCL for atmospheric N2O measurement

In this manuscript, a compact open-path gas sensor is developed for detection of atmospheric N2O. In such sensor, the wavelength modulation spectroscopy with 1f-normalized WMS detection strategy is employed to improve the detection sensitivity and eliminate the influence of light intensity fluctuations. The 20 ppm N2O standard gas is calibrated and the standard deviation is 0.011 ppm, which demonstrates it has high accuracy. Laboratory N2O air is continuously measured for 7 h and the standard deviation of the concentration is below 1.5 ppb. We use Allan deviation analysis to derive that N2O detection limit is 1.1 ppb at integration time of 1 s, and the sensitivity can be improved to 0.14 ppb at an optimal integration time of 95 s. The long-term stability of the developed sensor system is verified by a two-day real-time measurement in ambient air. The derived results well demonstrate our open-optical-path gas sensor system has a fast response, a good stability, a high sensitivity, and an excellent accuracy.