表面热透镜技术测量光学薄膜样品表面热变形
Measurement of thermal deformation using surface thermal lens technique
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摘要: 给出了连续调制激励光照射下光学薄膜样品表面热变形场的理论分布，并由此定义了表面热透镜（STL）信号。根据表面热透镜理论实验测量了一个BK7基底高反膜样品的形变，给出了表面热透镜信号随调制频率的变化曲线。实验结果表明：在采用的STL实验构型中，探测了最小1.985 nm的直流形变，对应不调制时的形变为3.97 nm，相应的形变探测灵敏度达到了10 pm量级；直流形变与功率成线性关系；交流表面热透镜信号随着频率增大而减小，在高频端近似成线性减小。Abstract: A theoretical model to describe the three-dimensional deformation distribution of an optical sample irradiated by a square-wave modulated laser is presented. The surface thermal lens(STL) signal is defined based on the deformation theory simultaneously. According to STL theory, the deformation of a highly reflective sample with BK7 substrate is measured experimentally. The results are in good agreement with deformation model. With our experiment configuration, a minimal 1.985 nm direct current (DC) deformation is measured, corresponding to 3.97 nm without modulation. The 10 pm detect limit for the deformation measurement is achieved in our experiment. The AC STL signal is also presented in the frequency domain.
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Key words:
- thermal deformation /
- optical coating sample /
- surface thermal lens /
- absorptance /
- detecting limitation
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