The absorption saturation under optically thick conditions will bring difficulties to laser spectroscopy gas sensing. We report the spectrum two wings reconstruction method and the transmitted laser intensity fitting method for tunable diode laser absorption saturation spectroscopy gas absolute measurements under optically thick conditions, and used the modified Lambert Beer's law to calculate methane concentration based on the incomplete spectrum of absorption saturation. The maximum deviation between the experimental measurement results and the standard methane concentration is about 4.7%, which verifies the feasibility of these new methods and also show that they have great potential for expanding the gas sensing range of a single absorption line.

中文翻译：

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光学厚条件下可调谐二极管激光吸收饱和光谱的气体传感方法

光学厚条件下的吸收饱和会给激光光谱气体传感带来困难。我们报告了光谱双翼重建方法和透射激光强度拟合方法在光学厚条件下用于可调谐二极管激光吸收饱和光谱气体绝对测量，并使用修正的朗伯比尔定律基于吸收饱和的不完整光谱计算甲烷浓度。实验测量结果与标准甲烷浓度的最大偏差约为4.7%，验证了这些新方法的可行性，也表明它们在扩大单条吸收谱线的气敏范围方面具有巨大潜力。