Rodriguez Luis G, Niemela Joseph, Cabrera Humberto
Appl Opt. 2023 Dec 1;62(34):9002-9008. doi: 10.1364/AO.500989.
We report on a pump-probe thermal lensing method for measuring the linear absorption coefficient of liquids by using interferometry and numerical analysis. The method is based on interferograms generated when a localized photothermal effect is induced in the sample. The photothermal effect itself is induced by a pump beam impinging on a sample located on-axis of the probe beam, which is one of the paths of a Mach-Zehnder interferometer. A digital camera is employed as the acquisition device allowing the capture and storage of the experimental data. During the experiment, a total of three photographs are taken and stored on a personal computer, and by using an algorithm, the numerical analysis is done. Numerical analysis is subsequently used to calculate the photothermal phase difference and the normalized spatial distribution of the pump beam irradiance. Plotting the phase difference as a function of the spatial distribution of the pump beam produces a linear dependence from which the linear absorption coefficient is obtained. The sensitivity of the method (/1500) is validated using ethanol, methanol, and carbon disulfide.
我们报道了一种利用干涉测量法和数值分析来测量液体线性吸收系数的泵浦-探测热透镜方法。该方法基于在样品中诱导产生局部光热效应时生成的干涉图。光热效应本身是由泵浦光束照射位于探测光束轴线上的样品而引发的，探测光束是马赫-曾德尔干涉仪的光路之一。使用数码相机作为采集设备，用于捕获和存储实验数据。在实验过程中，总共拍摄三张照片并存储在个人计算机上，然后通过一种算法进行数值分析。随后利用数值分析来计算光热相位差和泵浦光束辐照度的归一化空间分布。将相位差作为泵浦光束空间分布的函数进行绘图，会得到一种线性关系，由此可获得线性吸收系数。使用乙醇、甲醇和二硫化碳验证了该方法的灵敏度（/1500）。
