基于准布儒斯特角法研究抛光过程中光学材料的表面质量

光学硬脆材料在机械加工过程中不可避免地形成表面/亚表面损伤,对器件性能、使用寿命等具有至关重要的影响。相较于磨削、研磨两种前道工艺,抛光阶段材料的损伤逐渐减少至极其微量的程度,而最终残留的损伤将伴随材料的使用全周期,研究抛光阶段表面质量的变化过程对掌握抛光的工艺质量十分必要,但测量难度高。针对这一问题,本文在总结抛光阶段损伤形式的基础上,首先仿真分析了准布儒斯特角法检测表面质量的原理和优势,随后以Nd∶GGG激光晶体为研究对象,利用椭偏仪对不同抛光工艺下样品表面质量的变化进行了实验研究。通过与白光干涉法测量的表面形貌进行对比,准布儒斯特角偏移量和相位角变化曲线斜率准确地反映了抛光过程中表面质量的变化,展现了该方法的无损伤和高灵敏度特性,以及辅助研究抛光工艺的可行性。最后,对准布儒斯特角法在表面质量检测方面面临的问题进行了分析和展望。

Study on surface quality of polished optical materials with quasi-Brewster angle method

Surface damages of optical materials are inevitably introduced during machining processes.These damages heavily degrade the working performance and lifetime of optical materials-based production.Compared to the machining process of grinding,the art of polishing smoothly removes the damage layer of the sample;however,it is often difficult to ensure the complete removal of the damage layer.Therefore,to determinethe sample's surface quality during polishing periods is very necessary despite difficulties in the measurement technique.Here,we analyzed the typical surface structure of a polished sample and studied the measurement principle of the quasi-Brewster angle method.Simulations show the advantages of this approach to characterize the surface quality of a polished optical plate.As a demonstration,Nd∶GGG optical plates were polished with different processing time and tested carefully with a spectroscopic ellipsometer.Compared with the surface topography measured by white light interferometry,the quasi-Brewster angle offset and the slope of the phase-angle change curve accurately reflect the changes of surface quality during polishing,indicating that the quasi-Brewster angle method has a high sensitivity to the surface roughness and subsurface damages of the sample.This also implies the possibility of the proposed method in characterizing the changes of the surface quality under polishing progress.Finally,the future development trend of subsurface damage detection technology for polishing process.