Ion Beam Polishing Fused Quartz Component Physics And Laser Damage Characteristics Research

Laser damage resistance ability of optics has become the one of the "bottleneck" problems to limit the high power output of solid laser devices. To remove the surface and sub-surface impurities and defects is one of the important methods to improve the laser damage resistance capability. Fused silica is the largest amount of material in laser systems, and ion beam etching as controllable non-contact processing can not affect the surface quality (including surface roughness, surface, residual stress) under the premise of effectively removing or passivating the surface and sub-surface defects of fused silica. It is a very promising surface treatment technique.Ar ion beam polishing technology is used to remove or passivate the surface and subsurface defects in fused silica. Firstly, the computer simulation on experimental parameters is performed to obtain the optimized parameters. Then the surface morphology, roughness,transmission wavefront as well as laser induced damage threshold are studied for the ion beam polished fused silica optics.The SRIM code is used to simulate the physical process during Ar ion beam etching of fused-silica and the results show that:(1) Ion beam etching efficiency increases with the increasing ion energy. The rate firstly increases with the increasing incident angle from0°to60°, and the maximum appears at60°, and then decreases. When the incident angle is90°, no etching occurs.(2) In the same incident angle, the projected range of Ar ion implantation increases with the increasing ion energy. Considering the etching efficiency and projected range, the ion energy is selected below lkeV in order to avoid the damage induced by high energy.The experimental results showed that:(1) Ar ion beam polishing can remove the residual polishing powder impurities embedded in the surface defects to improve the laser induced damage threshold of fused silica.(2) Ar ion beam polishing can passivate or remove thesurface defects in the surface of fused silica induced silica induced by mechanical polishing. The scratches can be well removed. Therefore, the laser induced damage threshold can be enhanced by ion beam polishing.(3) Ion beam polishing has no obvious effect on the surface roughness and transmission wavefront of optics.(4) Ion beam etching effect strongly depends on the cleanliness of the equipments. If the ion beam equipment is clean, the polishing effect is good. However, when the cleanliness becomes worse, the surface pollution is becoming more and more serious and even reduces the laser induced damage threshold. Therefore, the equipment cleanliness should be strictly controlled to ensure the polishing effect.