脉冲激光光热失调技术

Pulsed Laser Photothermal Detuning Technique

将脉冲激光作为加热光引入光热失调测量技术中,提出了脉冲激光光热失调测量技术,介绍了其基本原理,分析了脉冲激光光热失调测量技术用于测量光学薄膜微弱吸收的可行性。实验以532 nm的高反射光学薄膜为样品,采用波长为632.8 nm的探测光,研究了脉冲激光光热失调技术信号振幅的时间特性以及最大信号幅值与样品表面加热光能量密度、加热光斑与探测光斑相对位置的变化关系。研究结果表明,光热信号随时间先增大后减小,而随表面加热光能量密度的提高而增大,当样品表面加热和探测光斑重合时光热信号最大。

A pulsed laser photothermal detuning technique, in which the temperature induced spectral shifts of optical coatings are used to measure photothermal signal, is presented. A theoretical model is developed to describe the pulsed laser photothermal detuning signal. The application to the absorption measurement of optical coatings is discussed. An experiment is performed with a highly reflective （HR） coating used in 532 nm. The amplitude and temporal behavior of the pulsed laser photothermal detuning are detected at 632.8 nm, and their dependences on the experimental parameters, such as the energy density of excitation and probe beams on the sample surface are the excitation beam and the relative position between the investigated. The results show that the detuning signal increases firstly and then decreases with the time, rises with the increase of the power density, and reaches the maximum at the position where the pump and probe beams are overlapped.