激励光辐照薄膜的表面热透镜效应中,调制频率的大小影响样品内热波的热扩散深度。通过频率控制热波扩散深度可以探测不同薄膜层面的吸收和热缺陷分布。理论分析了不同薄膜厚度下调制频率对热扩散深度的影响。结果表明,薄膜的热导率越小、膜厚越厚,基底中的热扩散深度就越浅,不同材料的基底对吸收测量带来的影响就越小;在膜厚一定的情况下,调制频率越高,基底中的热扩散深度越浅,不同基底样品的光热信号将趋于相等。 In the thermal lens effect of the surface of the thin film irradiated by the excitation light, the modulation frequency affects the thermal diffusion depth of the heat wave in the sample. By controlling the depth of thermal wave diffusion, the distribution of absorption and thermal defects at different film planes can be detected. The influence of different modulation frequency on the heat diffusion depth is theoretically analyzed. The results show that the smaller the thermal conductivity of the thin film, the thicker the film thickness, the shallower the depth of thermal diffusion in the substrate, the smaller the influence of the substrate of different materials on the absorption measurement; in the case of a certain film thickness, The higher the frequency, the shallower the heat diffusion depth in the substrate, and the photothermal signals of different substrate samples will tend to be equal.