大口径钛宝石晶体全频域透射波前误差高精度加工工艺研究  

High-Precision Transmission-Wavefront-Processing Technology of Large Aperture Ti∶sapphire Crystal at Full Spatial Frequency

作　　者：金寿平 付跃刚[1] 金钰皓 郝志旭 Jin shouping;Fu Yuegang;Jin Yuhao;Hao Zhixu(School of Opto-Electronic Engineering , Changchun University of Science and Technology ,Changchun , Jitin 130022, China;Taiyuan University of Technology , Taiyuan , Shanxi 030024, China)

机构地区：[1]长春理工大学光电工程学院,吉林长春130022 [2]太原理工大学,山西太原030024

出　　处：《中国激光》2019年第9期129-138,共10页Chinese Journal of Lasers

基　　金：国家自然科学基金(61705018)

摘　　要：钛宝石晶体是超强、超短脉冲激光振荡源广泛采用的工作物质,其口径大小和表面全频域波面误差决定了超短、超强激光系统的输出能量和光束质量,然而由于大口径钛宝石晶体光学均匀性差及硬度高的特点,其实现高精度透射波前和超光滑表面加工很具挑战性。针对这一问题,设计了线偏振干涉光源检测方法,解决了钛宝石晶体双折射导致的透射波前检测干涉条纹无法解析的问题;基于对钛宝石晶体材料光学均匀性的检测分析,发展了基于单轴机的透射波前快速抛光收敛工艺;通过正交实验和灰关联分析法,利用小磨头抛光工艺实现了钛宝石晶体高精度透射波前低频误差和超光滑表面高频误差的加工;为改善中频误差,发展了基于硅溶胶抛光液的小磨头中频误差光顺工艺。实验结果表明:多手段组合的加工工艺可以实现大口径钛宝石晶体全频域透射波前误差的有效控制,针对直径为120 mm的钛宝石样件,透射波前峰谷值可达0.283λ(λ=632.8 nm),中频功率谱密度无明显的特定频段调制误差,高频表面粗糙度R_q约为0.262 nm,可达到超光滑量级。Ti∶sapphire crystal is a widely-used working material for ultra-short and ultra-intense laser oscillator. Its aperture and surface full-spatial-frequency wavefront errors determine the output energy and beam quality of ultra-short and ultra-intense laser system. However, owing to the extreme difficulty in obtaining good optical homogeneity and high Mohr hardness in the Ti∶sapphire crystal, it remains a great challenge to fabricate a large-aperture Ti∶sapphire with a high-precision transmission wavefront and super-smooth surface. High-precision transmission-wavefront measurements of the Ti∶sapphire crystal are realized through the design of a linear polarization interference detection method to match the crystal axis, which solves the problem that the interference fringes of transmission-wavefront measurements cannot usually be resolved owing to the birefringence caused by the structural characteristics of the Ti∶sapphire crystal. Based on the measurements and analysis on the optical homogeneity of the Ti∶sapphire crystal, a fast polishing convergence process for the transmission wavefront is developed using an uniaxial machine. In order to realize the process for transmission wavefront with high accuracy and low frequency error and the process for super-smooth surface with high frequency error, orthogonal experiments combined with the grey relational analysis method are used to optimize the processing parameters of a computer-controlled small-grinding-head polishing. A small-grinding-head smoothing process using silica sol polishing fluid is developed to reduce the mid-spatial-frequency errors. Experimental results show that the transmission-wavefront errors of the large-aperture Ti∶sapphire crystal at full spatial frequency can be effectively controlled by using multi-way processing technologies. For a large-aperture Ti∶sapphire crystal with a diameter of 120 mm, the peak-valley value of the transmission wavefront can reach 0.283λ(λ=632.8 nm), the power spectral density of intermediate frequenc

关 键 词：材料 钛宝石晶体 透射波前 超光滑表面 

分 类 号：O436[机械工程—光学工程]