阶跃光激励的光热偏转技术的理论研究

Theoretical Research of the Photothermal Deflection Technique with Step Optical Excitation

基于光热偏转技术,在阶跃光激励下,样品和偏转媒质的一维温度分布和光热偏转信号幅度将随时间和空间发生变化.利用拉普拉斯变换求得其温度分布和信号幅度的表达式,并计算模拟偏转媒质的温度场、温度梯度随时间的变化,以及探测光离样品表面不同距离时的信号变化规律,分析偏转信号幅度随材料热扩散率大小的变化规律.模拟结果表明,光热偏转信号幅值及样品表面空气的温度梯度均随离样品表面的距离增加而变小,信号幅值上升与下降的快慢受样品的热扩散率的影响较大.

Based on the photothermal deflection technique(PDT)with step optical excitation,the one-dimensional temperature distribution and photothermal deflection signal amplitude of the sample and deflection medium will change with time and space.The expressions of temperature distribution and signal amplitude are obtained by Laplace transform.The temperature field and temperature gradient of the deflection medium with time and the signal variation law of the probe beam at different distances from the sample surface are simulated.The variation of deflection signal amplitude with material thermal diffusivity is analyzed.The simulation results show that the temperature gradient decreases with the increase of the distance from the sample surface,The farther the probe beam is from the sample surface,the smaller the PTD signal and the slower the signal rises and falls.The greater the thermal diffusivity of the sample,the faster the signal rises and decreases.