连续和准连续激光调制谱分析技术的比对研究

为了在面对不同检测需求时,能够选取适合的调谐激光吸收光谱技术方案,对直接吸收光谱、连续调制谱和准连续调制谱三种方法进行了理论分析和实验比较。在相同实验条件下,通过同一激光器测量不同浓度CO2气体,比较了这三种方法的技术特点、信号特征、检测灵敏度。结果表明,准连续调制谱技术具有与连续调制谱相当的检测灵敏度,但是受激光能量间断和较大的寄生幅度调制影响,检测信号相对于气体吸收谱的线形失真较大,因此不太适合依赖光谱线形和线宽的压力、流速测量。为选取更加适用的激光调制谱技术,提供了参考依据。

Comparison of quasi-continuous and continuous tunable diode laser absorption spectroscopy for gas detection

The theoretical analysis of the direct absorption spectroscopy, the continuous modulation spectroscopy and the quasi-continuous modulation spectroscopy was shown and the corresponding experiments were carried out in order to choose the adequate scheme of the laser modulation spectroscopy to satisfy different requirements of the detection. CO2 gas with different concentrations was detected under the same experimental conditions by using the three different modulation techniques with the same laser. Technical characteristics, signal features and detection limits were compared respectively. Results showed that the detection limit of the quasi-continuous modulation spectroscopy was approaching to that of the continuous modulation spectroscopy. However the linear distortion of the detection signal was obvious, because of the effects of laser energy intermittent and parasitic amplitude modulation on the line shape. Therefore the quasi-continuous modulation spectroscopy is not suitable for the pressure and flow measurements, which closely depend on the line shape. This work has provided reference for selections of the laser modulation spectroscopy.