Li B, Welsch E
Institut für Optik and Quantenelektronik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany.
Appl Opt. 1999 Aug 20;38(24):5241-9. doi: 10.1364/ao.38.005241.
The Fresnel diffraction integral is used directly to describe the thermal lens (TL) effect with a mode-mismatched collinear configuration. The TL amplitudes obtained with Gaussian, Airy, and top-hat beam excitations are computed and compared. Numerical results for beam geometries optimized for both near- and far-field detection schemes are presented, and the analytical results developed by Bialkowski and Chartier [Appl. Opt. 36, 6711 (1997)] for a Gaussian beam TL effect are summarized in simplified form. Both the numerical and the analytical results demonstrate that, under a beam geometry optimized for either near- or far-field detection, the Gaussian beam TL experiment has approximately the same maximum signal amplitude as does the photothermal-interference scheme. A comparison between the optimum near- and far-field detection beam geometries indicates that a practical mode-mismatched TL instrument should be based on the far-field detection geometry. The computation results further demonstrate that the optimum beam geometry and the TL amplitude depend largely on the excitation-beam profile. The top-hat beam TL experiment is approximately twice as sensitive as the Gaussian beam TL scheme.
菲涅耳衍射积分直接用于描述模式失配共线配置下的热透镜（TL）效应。计算并比较了高斯光束、艾里光束和平顶光束激发下的TL振幅。给出了针对近场和远场检测方案优化的光束几何形状的数值结果，并以简化形式总结了Bialkowski和Chartier [《应用光学》36, 6711 (1997)] 针对高斯光束TL效应得出的分析结果。数值结果和分析结果均表明，在针对近场或远场检测优化的光束几何形状下，高斯光束TL实验的最大信号振幅与光热干涉方案大致相同。近场和远场检测最佳光束几何形状之间的比较表明，实际的模式失配TL仪器应基于远场检测几何形状。计算结果进一步表明，最佳光束几何形状和TL振幅在很大程度上取决于激发光束轮廓。平顶光束TL实验的灵敏度约为高斯光束TL方案的两倍。
