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

Area of Science:

• Spectroscopy
• Analytical Chemistry
• Physical Chemistry

Background:

• Direct absorption spectroscopy (DAS) traditionally requires complex setups.
• Differential optical absorption spectroscopy (DOAS) often uses dual-path systems and sophisticated algorithms.
• Laser power fluctuations can impact the accuracy of absorption measurements.

Purpose of the Study:

• Introduce a novel absorption line shape recovery method for DAS.
• Enhance DAS systems with self-calibration and simplified implementation.
• Validate the reliability and self-calibration of the new method.

Main Methods:

• Developed a single-path DAS system, simplifying the traditional dual-path DOAS.
• Implemented a self-calibration function to mitigate laser power fluctuations.
• Utilized analog or digital filters for direct absorption profile recovery, avoiding complex fitting algorithms.

Main Results:

• Successfully validated the novel DAS method using a CH4 transition at 1653.72 nm.
• Demonstrated immunity to laser power fluctuations through the self-calibration function.
• Optimized Voigt fitting residuals and signal-to-noise ratio, showing comparable or improved performance against DOAS.

Conclusions:

• The novel DAS method offers ultra-easy implementation and robust self-calibration.
• This technique provides a simplified and reliable approach for absorption line shape recovery.
• The method shows promise for various spectroscopic applications requiring high accuracy and ease of use.