The Influence Of The Surface Quality Of Optical Components On The Characteristics Of Laser Damage

With the widespread use of large high-powered laser devices,the problem of laser-induced damage of optical materials has received more and more attention and research from scholars.For precision optical components,the laser damage of optical components is closely related to their surface microstructure,which depends on their fabrication process.Therefore,in this thesis,the correlation between laser damage characteristics and surface quality of optical components under YAG laser irradiation with a wavelength of 1064 nm is investigated from the perspective of the processing process using theoretical analysis,simulation and experimental methods.The main research contents and their results are as follows.(1)On the basis of the study of the theory of laser-induced damage of optical components,the temperature and stress field distributions of coated and uncoated components were simulated and analyzed by COMSOL Multiphysics software under laser irradiation with certain energy density,and the temperature and stress trends of optical components under laser irradiation were obtained.(2)The correlation between the surface microscopic features of optical components and the processing process was investigated.K9 and fused silica materials were used as experimental samples,and the surfaces of the samples were processed by conventional polishing,magnetorheological polishing and ion beam polishing,followed by surface morphology tests,and the results showed that the surface microstructures of optical elements prepared by different polishing processes were also different.(3)The correlation between the laser damage characteristics of optical components and the processing process was investigated.The surfaces of the optical components were processed to the same magnitude of about 2 nm by different polishing methods,and then the polished samples were tested for laser damage,and the surface morphological changes of the samples before and after laser irradiation were compared and analyzed from several angles.The final results show that the damage morphology of optical components prepared by different polishing methods varies under laser irradiation,and there are also differences in the laser damage threshold.From the results of scatterometry,optical microscopy and white light interferometer,the optical components processed by ion beam polishing are more resistant to laser damage,followed by magnetorheological polishing and the weakest by conventional polishing.(4)The near-infrared laser damage characteristics of the coated samples were investigated.A single-layer SiO2 antireflection film 90 nm thick was deposited on the surface of the sample by the same coating technique,and the laser damage test was carried out.The results show that the damage patterns of coated optical elements prepared by different polishing methods are closely related to the optical material itself under laser irradiation.The damage pattern of the coated K9 element showed large and regular shaped holes,while the damage pattern of the coated fused silica element showed smaller and irregular shaped holes with black ablation marks and cracks around the holes.The laser damage threshold of coated components is not only related to the processing method of the components,but also closely related to the material body.As far as the processing method is concerned,the laser damage threshold of coated components with ion beam polishing is the largest,followed by magnetorheological polishing and conventional polishing is the smallest;as far as the material body is concerned,the laser damage thresholds of coated fused silica components processed by different polishing methods are larger than those of coated K9 components.The results of this thesis provide a further understanding of laser damage to optical components,showing the influence of the surface quality of optical components under different processing processes on the laser damage characteristics,and providing a scientific basis and technical foundation for the manufacturing process of optical components in intense laser systems or anti-intense laser systems.