Sensitivity Enhancement of a Miniaturized Nonresonant Photoacoustic Spectroscopy CO₂ Sensor

This study introduces a photoacoustic spectroscopy (PAS) gas sensor based on an all-in-one nonresonant photoacoustic cell. A finite element model (FEM) of the sensor taking into account both photoacoustic and thermoacoustic signal is constructed. The key structural parameters of the all-in-one photoacoustic cell are carefully optimized and determined through simulation and then validated in experiments. The calibration results of the sensor demonstrate a maximum sensitivity of 0.207 mV per <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>L/L in a measurement range of 0–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5000~\mu $ </tex-math></inline-formula>L/L. Moreover, the proposed sensor is capable of achieving a fast response of 13 s, a detection limit of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.14~\mu $ </tex-math></inline-formula>L/L, a measurement repeatability of 0.34%, and a high resistance to interference from humidity. The compact footprint and optimal performance of the proposed photoacoustic gas sensor make it a suitable to a broad spectrum of applications.