The existence of a signal baseline due to a variety of reasons in a photoacoustic (PA) gas measurement system is a common phenomenon. One major component is the absorption of optical windows in an enclosed PA cell. This work explores the relation between the background signal and the thermoelastic effect inside the windows by modelling the pressure and elastic wave field by means of a Green-function based method. The influence of laser incidence location, angle and radius is discussed based on a rigorous three-dimensional solid-to-fluid coupling model. The effects were theoretically demonstrated culminating in the determination of best (minimum background signal) performance using a collimated and expanded incident laser beam. The results were also validated through experiments.

由于多种原因，光声（PA）气体测量系统中存在信号基线是一种常见现象。一个主要组成部分是封闭式PA电池中光学窗口的吸收。这项工作通过使用基于格林函数的方法对压力和弹性波场进行建模，探索了背景信号与窗户内部的热弹性效应之间的关系。基于严格的三维固液耦合模型，讨论了激光入射位置，角度和半径的影响。从理论上证明了这些效果，最终证明了使用准直和扩展入射激光束确定最佳（最小背景信号）性能。通过实验也验证了结果。