Laser-induced wavefront distortion is detectable by several techniques based on the photothermal effect. The effect is probed by monitoring the phase shift caused by the bulging of the heated area, the photoelastic effects, and the spatial distribution of the refractive index within the sample and in the fluid surrounding it. A simple analytical solution for the wavefront distortion was only possible for low absorbing materials, with the assumption that the stresses obey either the thin-disk or the long-rod type distributions. Recently, a unified theoretical description for the laser-induced optical path change was proposed to overcome part of this limitation for weakly absorbing materials, regardless of its thickness. In this work, we perform an experimental investigation taking the sample–fluid heat coupling effect into account using the thermal lens technique. The experimental investigation presented here validates the unified model. In addition, we show that the heat-coupling model provides an alternative method to obtain physical properties of non-absorbing fluid by using a reference solid sample.

中文翻译：

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热透镜技术中样品-流体热耦合效应的实验研究

激光引起的波前畸变可以通过几种基于光热效应的技术来检测。通过监测由加热区域的膨胀、光弹性效应和样品内及其周围流体中的折射率的空间分布引起的相移来探测这种效应。波前畸变的简单解析解仅适用于低吸收材料，假设应力服从薄盘或长杆型分布。最近，提出了对激光诱导光路变化的统一理论描述，以克服弱吸收材料的部分限制，无论其厚度如何。在这项工作中，我们使用热透镜技术进行了考虑样品-流体热耦合效应的实验研究。这里介绍的实验研究验证了统一模型。此外，我们表明热耦合模型提供了一种替代方法，可通过使用参考固体样品获得非吸收性流体的物理特性。