Study on the Laser Characteristics for Calibration-Free Wavelength Modulation Spectroscopy

Abstract

In this paper, a calibration-free wavelength modulation model via tunable diode laser absorption spectroscopy was setup. The laser modulation characteristics, modulation depth, linear modulation amplitude and frequency shift, were measured for the model setup. The experimental results show that modulation depth and the linear intensity modulation amplitude have well linear fitting to the scan voltage. Based on the laser parameters, the calibration-free model can be used to infer the gas temperature.

Frequency modulation characteristics for interband cascade lasers emitting at 3 μm

“…In addition, a number of refinements to the WMS model above are typically made to realize calibration-free measurements, e.g., WMS with the second harmonic normalized by the first harmonic (WMS-2f/1f) [22,23], as well as the phasor decomposition method using first-harmonic detection [24,25]. However, both of the improved methods still require accurate knowledge of the FM parameters of the laser, including the FM efficiency and the FM/IM phase shift.…”