Rodriguez Luis G, Niemela Joseph, Cabrera Humberto
Universidad Técnica de Manabí, Facultad de Ciencias Básicas, Departamento de Física, Avenida Urbina, Portoviejo, 130105, Ecuador.
MLAB, STI Unit, The Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy.
Heliyon. 2023 Sep 27;9(10):e20492. doi: 10.1016/j.heliyon.2023.e20492. eCollection 2023 Oct.
A thermal lensing approach based on parabolic approximation and Mach-Zehnder interferometer for measuring optical absorption and thermal diffusivity coefficients in pure solvents is described in this work. The approach combines the sensitivity of both thermal lensing methods and interferometry techniques. The photothermal effect is induced by a pump laser beam generating localized changes in the refractive index of the sample, which are observed as a shift in phase of the interference pattern. Each interference pattern is recorded by means of a digital camera and stored as digital images as a function of time. The images are then numerically processed to calculate the phase shifting map for a specific time. From each phase shifting map, the experimental phase difference as a function of time is calculated giving a phase-time transient, which is fitted to a mathematical model to estimate the optical absorption and thermal diffusivity of the sample. The experimental results show that the sensitivity is approximately λ/4800 for the minimum phase difference measured.
本文描述了一种基于抛物线近似和马赫-曾德尔干涉仪的热透镜方法，用于测量纯溶剂中的光吸收系数和热扩散系数。该方法结合了热透镜方法和干涉测量技术的灵敏度。泵浦激光束诱导光热效应，使样品的折射率产生局部变化，这种变化表现为干涉图样相位的偏移。每个干涉图样通过数码相机记录，并作为时间的函数存储为数字图像。然后对图像进行数值处理，以计算特定时间的相移图。从每个相移图中，计算出作为时间函数的实验相位差，得到相位-时间瞬态，将其拟合到数学模型中，以估计样品的光吸收和热扩散系数。实验结果表明，对于测量的最小相位差，灵敏度约为λ/4800。
