| Fused silica optical components are widely used in high power solid-state laser devices.However,the anti-reflective film coated on surface of fused silica to enhance its transmittance tends to be susceptible to damage by laser and be polluted by the service environment.In addition,it is easy to form ablated debris and raised ring around the mitigated pit because of the large power when CO2 laser is used to mitigate large defects on surface of fused silica.It is susceptible to damage and accelerate the growth of the damage under intense laser irradiation if these large potential safety hazard in the optical film,ablated debris and raised ring do not be removed.Thus,the damage threshold of components will be reduced greatly.Therefore,how to improve the laser damage threshold and prolong its service life has become a hot topic in the research of high power solid-state laser.In this thesis,ion beam etching technology is used to remove tripled-frequency film coated on surface of fused silica and ablation fragments or raised ring around the mitigated area of fused silica optical components to obtain a clean and smooth surface.It can improve its damage threshold when the surface of fused silica optical components was modified.The main contents of this work are carried out from the following aspects:(1)The basic principle of ion beam etching is analyzed from the perspective of physical etching mechanism,to master the process of ion beam etching.The main influence factors for ion beam etching include energy,incident angle,flux of ion beam and atomic number of ions.(2)TRIM software is used to simulate the physical process of surface etching by using Ar+ ion beam to obtain the correlations between ion energy,incident angle and etching rate,etching depth,damage degree,respectively after simulating the physical process of using Ar+ to etch the surface of quartz by TRIM software.(3)The experiments of Si O2 film removal from the surface of K9 glass are conducted and it is found that there is some deviation between the experimental results and simulated results,their overall variation trend is consistent.(4)The experiments of removing tripled-frequency films coated on surface of fused silica has been accomplished based on the results of TRIM simulation and the experimental results of removing Si O2 film coated on surface of K9 glass.it was verified that ion beam etching technology used to remove tripled-frequency films from the surface of fused silica was feasible.At the same time,the energy of ion beam for the best etching effect has been obtained.(5)The geometric model is constructed on the basis of the structural characteristics of ablation debris and raised ring.The ion beam etching parameters are theoretically obtained according to the geometric model and the previous etching resutls.Then the experiment of ion beam to remove ablation fragments and raised ring around the mitigated area of fused silica was carried out and it verified the feasibility of using the ion beam etching technique to remove ablation and raised rings of the mitigated area on the surface of fused silica. |
