Study Of Defects In Damaged And Repaired Fused Silica Optical Elements

Laser-induced damage of fused silica under strong ultraviolet laser has always been a major problem in high-power solid-state laser devices.The damage threshold and damage growth threshold of fused silica are not conducive to development of related scientific research,and have also improved the cost of the experiment.Repairing and reusing damaged optical components can reduce the cost of scientific research to a certain extent,contribute to the steady advancement of related scientific research,help to reveal the damage mechanism more deeply,and help increase the damage threshold.Raman spectroscopy,infrared spectroscopy,and fluorescence spectroscopy are employed to study the relationship between the type,the distribution,the content of defects and damage threshold in damaged and repaired fused silica optical components.The detection system was designed and implemented for the large-caliber fused silica components.There are six chapters in this thesis.The first chapter introduces the structural properties,the defects and laser induced damage of fused silica.the defect characteristics of fused silica,the induced damage under ultraviolet laser,the damage threshold measurement method,the mitigation method and related research progress.Chapter two briefly introduces the methods used in this paper to characterize the damage and repair of fused silica,including Raman spectroscopy,infrared spectroscopy,fluorescence spectroscopy,and scanning electron microscopy.In the third chapter,Raman spectroscopy and infrared spectroscopy were employed to analyze the structure of fused silica before and after mitigation.The damage threshold before and after mitigation are compared.According to the experimental results,the CO2 laser can effectively repair the damaged points of the fused silica optical element by heating,melting or evaporating.By adjusting the parameters of the CO2 laser,annealing the fusion repair area can also effectively reduce the residual stress in the repair area.In the fourth chapter,fluorescence spectroscopy was employed to study the damaged and repaired area of fused silica components.and the defect characteristics were analyzed.The relevance between fluorescence spectrum and damage threshold was proposed,the influence of total defect content and characteristic defect content of fused silica material on damage threshold is summarized.In the fifth chapter,based on Raman spectroscopy technology,by refining the characterization methods and details of fused silica materials,a Raman spectroscopy non-destructive rapid detection system for large-size fused silica optical components was designed and built.Chapter six summarizes all the research results.