Rapid and precise partial pressure measurement of multiple gas species with mid-infrared electro-optic dual-comb spectroscopy

In order to overcome the shortcoming of the TDLAS method, a partial pressure measurement method based on dual comb spectroscopy is proposed. The comb-based partial pressure measurement system comes with excellent performance in nearly all criteria: high detection sensitivity, high measurement speed, and synchronous survey of multiple-gas partial pressures. The experimental system was built in the mid-infrared band of 88.42–90.10 THz with a spectral resolution of 54.5 MHz and used for partial pressure measurement of CH₄ and C₂H₄. Two electro-optics (EO) optical frequency combs (OFC) with a repeat frequency of ～25 GHz are spectrally interpolated to increase spectral sampling ratio using an acousto-optic frequency shifter, so that they could be utilized for high-resolution gas sensing. The measurement result demonstrates the excellent performance of this system in partial pressure measurement. The deviation of the measurement results of two gases CH₄ and C₂H₄ from the true value are about 3%. Moreover, once the gas absorption line strength is accurately calibrated, the accuracy of partial pressure measurement will be further improved.