Research On Defect Passivating Technique For Ultraviolet Fused Silica Optics

Fused Silica optics have been widely utilized in high-power laser systems, while the optics’ low manufacture efficiency as well as laser-induced damage threshold limit the system’s further development largely. Thus, the manufacture of fused silica optics with both high efficiency and damage threshold is demanded urgently in engineering and has a promising future. This thesis aims at solving theoretical as well as technical problems relating to high efficiency and damage threshold manufacture. Meanwhile, the thesis researches the defect passivating effect of magnetorheological finishing and HF etching processes via theoretical analysis, Finited Different Time Domain algorithm simulation, technique experiments and combined process fabrication experiment. Furthermore, the mechanism of threshold raising after being processed is also researched. Our research works include:(1)The relationship between simulation results and actual threshold is established and threshold influence of typical structural defects is also simulated utilizing Finited Different Time Domain algorithm. The results indicate that for structural defects, its width/ depth ratio affects the optics threshold mainly, more exactly, larger the ratio is, the higher threshold will be. The simulation results provided a valid threshold evaluating tool which could guide further research conveniently.(2)The defect passivating effect of magnetorheological process is put forward and experimentally proved. The effect indicates that, near defect areas, magnetorheological finishing keeps defect width, shallows depth and enlarges the width/depth ratio rather than maintains the initial defect shape when removing materials. According to simulation, this effect can raise threshold significantly. Then, the passivation models are established for both processes based on experiment data. Correspondingly, the threshold decline models are also put forward. These works solid technical foundation for the final realization of threshold rising.(3)The threshold raising is explained from the view of defect’s passivation and realized by magnetorheological finishing and HF etching combined experiments. Compared this defect-carrying sample to the defect-free one, process time is shortened obviously from 1100 to 385 minutes and threshold is merely decreased from19.4 to17.8 J/cm2. Due to the optimized technique, the fabricating time was shorted by 2.6 times while the threshold decreased merely 8.2%.In summary, aiming at high efficiency and damage threshold optical manufacture, the thesis explores that how magnetorheological finishing and HF etching process raise damage threshold, refers that structural defects on optics could be passivated by magnetorheological finishing, and answers the question that why the combined technique can raise damage threshold. Besides, a threshold evaluating tool is also established. The achievements in the thesis improve the application of magenetorheological finishing and Hf etching combined process, embodies both significance in theoretical research and engineering application in the term of high efficiency and damage threshold manufacture of fused silica optics.