弱吸收测量中共光路表面热透镜系统的参量优化

为了提高热透镜法的测量精度,对表面热透镜法进行了测量技术分析,根据菲涅耳衍射定律和材料的热膨胀特性,建立了共光路表面热透镜测量的理论模型。利用该模型,分析了抽运光的能量大小,抽运光束和探测光束相对光斑大小,两光束相对偏移,测量时刻选择以及定标样品的选择等因素对测量现象和结果的影响。通过分析得到测量系统的一组最佳参量配置。分析表明,在设计测量系统时,应考虑定标样品的吸收特性。定标样品的选择原则是:在光热信号与吸收率的关系中,它与被测样品应处于同一个线性变化范围。

Parameters Optimization of Common Path System for Surface Thermal Lensing Detection in Weak Absorption

The surface thermal lensing effect method is a kind of sensitive absorption measurement technique.In order to improve its metrical precision,the parameters of measurement system must be optimized.The surface thermal lensing technique is investigated,and a theory model for common path measurement system is set up based on diffraction principle and material expanding characteristic.Applying this model,the factors which influence metrical phenomena and results are analyzed respectively,such as radius of the pump beam and probe beam,offset between two beams,measurement start time,and choice of scaled sample,and a best set of parameters configure is given.Results show that the absorptive characteristic of the scaled sample should be taken into account before measurement.The selective principle of scaled sample is that the photo-thermal signal should change linearly with absorption coefficient for both scaled and measured samples,the both absorption coefficients should be in the same linear range.