Trace gas detection system based on multi-reflection differential Helmholtz cell and VMD-airPLS algorithm

In this paper, a photoacoustic spectroscopy sensor based on multi-reflection differential Helmholtz cell and Variational Mode Decomposition-adaptive iteratively reweighted penalized least squares (VMD-airPLS) algorithm is proposed to improve the signal-to-noise ratio (SNR) and reduce the response time of the system. The Helmholtz photoacoustic cell, fabricated from brass, allows multiple reflections of the laser light within its resonant cavity , effectively increasing the gas absorption path by a factor of ∼ 6. The VMD-airPLS algorithm suppresses incoherent noise and slowly varying baseline noise over time. To validate the performance of the system, methane is measured using a laser with a wavelength of 1653.7 nm. Experimental results demonstrate a significant enhancement in the sensitivity of system, up to approximately 2.2 times, and an improvement in the SNR by up to approximately 4.2 times compared to single-pass system. The minimum detection limit for methane is ∼ 96.79 ppb. • A gas detection system utilizing a multiple reflection differential Helmholtz cell and the VMD-airPLS algorithm is proposed. • The multiple reflection cell enhances the light path by a factor of ∼ 6 and increasing sensitivity by a factor of ∼ 2. • The introduction of the VMD-airPLS noise reduction algorithm results in a 4.2-fold improvement in the signal-to-noise ratio.