A design methodology of miniature photoacoustic cell based on beam energy distribution and acoustic resonator coupling

Abstract

In photoacoustic spectroscopy, the photoacoustic cell plays the role of amplifying the photoacoustic signal, and the optimization of its parameters affects the sensitivity and dimensions of the whole system. However, none of the current optimization studies of photoacoustic cells have considered in depth the influence of beam waist radius, which limits the reduction of the size of photoacoustic cells. In this paper, based on the theory of photoacoustic spectroscopy, considering the inhomogeneity of the spatial distribution of the Gaussian beam energy and neglecting the loss of the beam in the acoustic resonator, a theoretical model of the effect of the beam waist radius on the cell constant of the first-order longitudinal resonant frequency is established. Six photoacoustic cells with different resonator radii were designed and measured for acetylene at five different beam waist radii. The relationship among beam waist radius, radius of acoustic resonator and cell constants shows that choosing a radius of resonator that matches the waist radius results in a more sensitive and smaller photoacoustic cell. The study provides a reference for the design of miniaturized photoacoustic cells with high sensitivity, thus promising to further improve the miniaturization of photoacoustic spectroscopy systems for more application scenarios.