A Fourier-domain-based line shape recovery method used in direct absorption spectroscopy.

A novel absorption line shape recovery method with self-calibration function and ultra-easy implementation was introduced to direct absorption spectroscopy (DAS) in this study. The self-calibration function empowered the DAS system with the immunity to the laser power fluctuations. The ultra-easy implementation was achieved in that the DAS system was substantially simplified with a single-path DAS rather than the traditional dual-path differential optical absorption spectroscopy (DOAS), and the absorption profile can be directly recovered by an analog or digital filter instead of complex fitting algorithm or sophisticated balance detection circuits. The reliability and self-calibration characteristic of the new method were validated using CH transition at 1653.72 nm, where the line strength is 1.45×10cm/molec. The Voigt fitting residual and signal to noise ratio were optimized in detail and compared with the DOAS.