Weak absorption detection method under broadband interference based on linear wavelength modulation spectroscopy

In complex environments, the measurement of trace gases is inevitably greatly affected by broadband absorption (such as water absorption in combustion exhaust). Based on the study of high-order harmonics in linear wavelength modulation spectroscopy, a method for detecting target gases (trace, weak absorption) in the presence of broadband absorption interference is proposed. Theoretical analysis and numerical simulation work give the applicable conditions of this method. The effectiveness of this method is verified by NO2 measurement of combustion exhaust gas. This study proves the application potential of this method for the measurement of trace gases under broadband absorption interference.