Study On A Laser Shock Post-processing Technique Of Optical Coatings Based On Laser Shock Wave

Optical coatings are the crucial components of laser system,and their laser-induced damages have always been one of blocks restricting the development of high-power laser systems.To improve the laser-induced damage resistance for coatings,some post-processing techniques have been proposed and researched.However,the application of the existing post-processing techniques is closely related to the coating material,coating stack,laser wavelength,and so on,making its own application conditions and application range restricted.Therefore,new post-processing techniques explored are vital.In this paper,the laser shock processing is applied as a post-processing technique on electron-beam coatings,the effect and mechanism of coatings treated by laser shock processing are researched.The contents are as follows:(1)The effect of laser shock post-processing(LSPP)on laser-induced damage resistance of 1?high-reflective coatings under single-pulse laser irradiation and its mechanism are investigated.The pure mechanical laser shock post-processing has evidenced a considerable promotion effect of laser-induced damage threshold(LIDT).Compared with the LIDT of 8J/cm~2without LSPP,the LIDT of 37J/cm~2of the high-reflective coating at an overlapping rate of 50%and laser energy of0.2J,increased by about 4.6 times.Using characterization methods to analyze the damage characteristics and mechanical properties for coatings before and after LSPP,the promotion mechanism is confirmed to be the comprehensive modification of the intrinsic defects and the mechanical properties.On the basis of experiments and theoretical analysis,the interaction equation of the total pressure in the laser shock area was established,which clarified the existence of the critical total pressure and provided a theoretical basis for selecting the optimal processing parameters.Simultaneously,through the synergy and competition between the packing density and surface roughness,LSPP reduced water absorption of porous coatings,without weakening its original optical performance.(2)The effect of LSPP on laser-induced damage resistance of 1?anti-reflective coatings under single-pulse laser irradiation and its mechanism are investigated.The results showed a great increase in laser-induced damage threshold(LIDT)for coatings at an overlapping rate of 30%or 50%and laser energy of 0.2J,and the reason for that is proved to be associated with the comprehensive modification of the intrinsic defects and the mechanical properties.Meanwhile,the effect of LSPP on water absorption characteristics for coatings is investigated.The results show that LSPP has no or a negative effect on the reduction of water absorption in anti-reflective coatings,which is possibly caused by surface roughness and packing density for coatings with LSPP that get worse.