In order to explore the feasibility of ion beam figuring (IBF) on DKDP crystal, the DKDP crystal machined by single point diamond turning (SPDT) was processed by IBF. This paper investigates the influence of IBF on DKDP crystal. Firstly, the surface quality and the photo-thermal absorption of DKDP crystal were measured respectively after SPDT and IBF. Then，the laser-induced damage threshold (LIDT) of two different processing crystals were tested by R-on-1 method. Finally, the mechanisms that the effect of IBF on LIDT were analyzed and discussed. After processing， the DKDP crystal remained intact. The surface quality satisfied the frequency tripping crystal requirement. However, due to the environmental impact, DKDP crystal had deliquescence, which contribute to decrease the LIDT of DKDP by 27.5%. IBF on DKDP is feasible，it is necessary to control the processing environment to avoid the crystal deliquescence.
To further improve the laser-induced damage threshold of fused silica elements after Hydrogen Fluoride (HF) acid dynamic acid etching, the effect of the nanoparticle SiO<sub>2</sub> jet polishing on the surface quality and laser damage properties of fused silica was studied. On the fused silica surface after HF acid dynamic etching, different depths were polished with nanoparticle SiO<sub>2</sub> jet, and their surface roughness were measured by In-situ detection. The photothermal absorption, laser damage threshold and surface contamination element concentration at different depths were measured. The experimental results show that the RMS value of the surface roughness of the surface is reduced from 1.440nm to 0.507nm, and surface contamination elements are removed. The laser damage threshold is improved by 10%. The results show that nanoparticle SiO<sub>2</sub> jet polishing can remove surface damage and contamination after HF acid dynamic etching on the basis of elastic processing. Therefore, laser damage threshold can be improved.
Potassium dihydrogen phosphate (KDP) crystals are essential components used in the high power laser applications. Its properties will affect the output power and quality of laser beam directly. To improve the laser-induced damage threshold (LIDT) of KDP crystal, this paper investigated the influence of ion beam figuring(IBF) technology on the laser damage properties of KDP crystal machined by single point diamond turning(SPDT). Firstly, the surface quality and photo-thermal absorption performance of samples were measured after turning and ion beam figuring. Then, the LIDT of crystal of different processing conditions were measured by R-on-1 test method. Finally, the mechanisms that ion beam figuring could improve the LIDT were analyzed and discussed.The experiment results show that ion beam figuring can reduce surface roughness,improve the surface quality as well as lower the absorption of KDP crystal elements, which contribute to increase the laser damage resistance of KDP crystals obviously.