Formation mechanism of a smooth, defectfree surface of fused silica optics using rapid CO2 laser polishing  

作　　者：Linjie Zhao Jian Cheng Mingjun Chen Xiaodong Yuan Wei Liao Qi Liu Hao Yang Haijun Wang 

机构地区：[1]State Key Laboratory of Robotics and System,Harbin Institute of Technology,Harbin 150001,People’s Republic of China [2]Research Center of Laser Fusion,China Academy of Engineering Physics,Mianyang 621900,People’s Republic of China

出　　处：《International Journal of Extreme Manufacturing》2019年第3期85-95,共11页极端制造（英文）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.51775147,51705105);Science Challenge Project(Grant No.TZ2016006-0503-01);Young Elite Scientists Sponsorship Program by CAST(Grant No.2018QNRC001);China Postdoctoral Science Foundation funded project(Grant Nos.2018T110288,2017M621260);Self-Planned Task(Grant Nos.SKLRS201718A,SKLRS201803B)of State Key Laboratory of Robotics and System(HIT);Fundamental Research Funds for the Central Universities(Grant No.HIT.NSRIF.2019053).

摘　　要：Surface defects introduced by conventional mechanical processing methods can induce irreversible damage and reduce the service life of optics applied in high-power lasers.Compared to mechanical processing,laser polishing with moving beam spot is a noncontact processing method,which is able to form a defect-free surface.This work aims to explore the mechanism of forming a smooth,defect-free fused silica surface by high-power density laser polishing with coupled multiple beams.The underlying mechanisms of laser polishing was revealed by numerical simulations and the theoretical results were verified by experiments.The simulated polishing depth and machined surface morphology were in close agreement with the experimental results.To obtain the optimized polishing quality,the effects of laser polishing parameters(e.g.overlap rate,pulse width and polishing times)on the polishing quality were experimentally investigated.It was found that the processing efficiency of fused silica materials by carbon dioxide(CO2)laser polishing could reach 8.68 mm2 s−1,and the surface roughness(Ra)was better than 25 nm.Besides,the cracks on pristine fused silica surfaces introduced by initial grinding process were completely removed by laser polishing to achieve a defect-free surface.The maximum laser polishing rate can reach 3.88μm s−1,much higher than that of the traditional mechanical polishing methods.The rapid CO2 laser polishing can effectively achieve smooth,defect-free surface,which is of great significance to improve the surface quality of fused silica optics applied in high-power laser facilities.

关 键 词：laser polishing mechanical processing smooth surface defect-free surface polishing rate 

分 类 号：TN249[电子电信—物理电子学] TH74[机械工程—光学工程]