Sensitivity dependence of optical parameters in a photoacoustic cell analyzed with a 2-D thermoelastic approximation.

Photoacoustic (PA) cell is an important component for PA spectroscopic trace gas measurement. However, its high responsivity towards light absorption in trace gases can be compromised to the background baseline generated from optical windows of the cell. In this research, a 2-D physical model considers double effects (thermoelasticity and thermoacoustics) was proposed to reveal the generation mechanism of the background spurious signal caused by absorption of the windows in a rectangular PA cell. The authentic PA signal due to gas absorption was modeled to obtain the signal-to-noise ratio (SNR) dependence of the best optical parameters. Beam collimation and dimensional conditions with respect to the SNR were discussed in detail, which was verified using an accurate finite element method. This proposed model exhibits flexibility and simplicity on straightforward sensitivity analysis in a PA cell and can avoid use of massive numerical calculation. • Laser in optical windows contributes baseline PA signal by thermoelasticity within. • 2-D approximation simplifies numerical calculation in obtaining theoretical baseline. • Window-generated background is due to desynchronized vibration states. • Collimated and expanded laser beam shows best performance in PA spectroscopic test. [ABSTRACT FROM AUTHOR]