IEEE Trans Ultrason Ferroelectr Freq Control. 2020 Jul;67(7):1470-1478. doi: 10.1109/TUFFC.2020.2973237. Epub 2020 Feb 11.
In this study, we present a quantitative photoacoustic (PA) method for performing absorption measurements on highly absorbing samples. Based on the thermoelastic mechanism, the relative changes in PA signal amplitude allowed the determination of absorption coefficients of materials in the 0.19-2500-cm range, with no prior knowledge of the material's optoacoustic properties required. We have tested our new methodology by performing absorption measurements on a series of planar liquid samples as well as gelatinized spherical samples. In this approach, laser-induced ultrasound waves were detected in transmission mode. With the model presented herein and a measurement of the relative change in amplitude of the PA signal at two different known concentrations, the absorption coefficient of the sample can be straightforwardly extracted. Three important advantages are highlighted by this analytical approach. First, no previous knowledge of the optical or acoustic properties of the sample is necessary. Second, only a small quantity of sample is required. Finally, our methodology includes both short- and long-pulse regimes, validating its use for any laser pulse duration so long as the requirement for thermal confinement is fulfilled. Remarkably, this new methodology performs best for thick, highly absorbing samples where traditional spectrophotometry is most challenging and unreliable, offering a promising alternative for quantification of the absorption properties of a range of diverse liquid, and gelatinous-state materials not amenable to conventional methods.
在这项研究中，我们提出了一种定量光声（PA）方法，用于对高吸收样品进行吸收测量。基于热弹机制，PA 信号幅度的相对变化允许确定材料在 0.19-2500-cm 范围内的吸收系数，而无需事先了解材料的光声特性。我们通过对一系列平面液体样品和凝胶化球形样品进行吸收测量来测试我们的新方法。在这种方法中，以透射模式检测激光诱导的超声波。通过本文提出的模型和对两个不同已知浓度下 PA 信号幅度相对变化的测量，可以直接提取样品的吸收系数。该分析方法具有三个重要优势。首先，不需要事先了解样品的光学或声学特性。其次，只需要少量的样品。最后，我们的方法包括短脉冲和长脉冲两种模式，验证了其对任何激光脉冲持续时间的适用性，只要满足热限制的要求。值得注意的是，这种新方法在厚的、高吸收样品中表现最佳，而传统分光光度法在这些样品中最具挑战性和不可靠，为量化一系列不同液体和不适用于传统方法的凝胶状材料的吸收特性提供了一种有前途的替代方法。
