中文摘要：

样品表面加热光斑和探测光斑的大小对光热技术有着重要影响,光热失调技术是一种新的可用于研究光学薄膜的微弱吸收的方法,文章理论分析了加热光斑和探测光斑尺寸对光热失调技术的影响。研究表明,加热光斑大小不变时,加热光调制频率增大,样品表面温升降低,温度分布区域减小;调制频率不变时,加热光斑越小,表面温升越大,分布区域越小。调制频率不变时,探测光斑越小,信号幅值越大,分布区域越小,信号幅值与加热光功率的线性关系的斜率越大,探测光斑的大小对信号幅频关系影响较小。研究结果对光热失调技术测量光学薄膜吸收具有重要意义。

英文摘要：

The beam size of the heating and probe laser play an important role in the photothermal technique.The photothermal detuning technique is a novel method,which can be used to study the weak absorption of optical coating.This paper mainly analyzed the influence of heating and probe beam sizes on the technique.The study shows that when the heating spot size fixed,the larger modulation frequency of heating beam,the smaller of both the temperature of sample surface and the area of temperature distribution. When the modulation frequency is a constant,the temperature of the sample surface increases and the distribution area reduces as the heating spot size decreases.And as the probe spot size decreases,the signal amplitude increases and the distribution area reduces too. Meanwhile,the slope of linear relationship between signal amplitude and the power of heating beam increases.The probe beam size has little influence on the relations of signal amplitude and modulation frequency.The results have important significance for absorption measurement of optical coating by the photothermal detuning technique.