| 摘 要： | N_2O is a significant atmospheric greenhouse gas that contributes to global warming and climate change. In this work,the high sensitivity detection of atmospheric N_2O is achieved using wavelength modulation spectroscopy(WMS) with an inter-band cascade laser operating around 3.939 μm. A Lab VIEW-based software signal generator and software lock-in amplifiers are designed to simplify the system. In order to eliminate the interference from water vapor, the detection was performed at a pressure of 0.1 atm(1 atm = 1.01325×10~5 Pa) and a drying tube was added to the system. To improve the system performance for long term detection, a novel frequency locking method and 2 f/1 f calibration-free method were employed to lock the laser frequency and calibrate the power fluctuations, respectively. The Allan deviation analysis of the results indicates a detection limit of ～ 20 ppb(1 ppb = 1.81205 μg/m~3) for a 1 s integration time, and the optimal detection limit is ～ 5 ppb for a 40-s integration time.
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