To realize the rapid repairing of surface damage of fused silica optics, a method combining magnetorheological and Computer controlled optical surface (CCOS) was proposed to quickly remove small size damage points on the surface of damaged fused silica optics. In this paper, the size and number of damage points on the surface of fused silica optics are analyzed. Meanwhile, the surface of the fused silica optics is evenly removed by the magnetorheological technology, and the change rule of damage points on the surface of fused silica optics is analyzed. After that, CCOS smoothing technology is used to restore the surface quality of the optics. The experimental results show that the combined technology can effectively remove the small size damage points on the surface of fused silica optics and maintain the surface quality of the optics, achieving a good repair effect.
To further increase the laser-induced damage threshold (LIDT) of calcium fluoride (CaF2), combined technique of chemical mechanical polishing (CMP) and acid etching as a function of removal mechanical defect and impurity contamination was investigated. After CMP process, the surface roughness reduced to Ra 0.68nm, the scratch and subsurface defect were mitigated which rise the LIDT to 8.6 J/cm-2. Due to the acid etching, the surface roughness of CaF2 elements increased to Ra 0.8nm, while the LIDT reached 11 J/cm-2, benefit from the elimination of impurity contamination. The result laser-induced damage test shows that, comparing to mechanical abrasive polishing (MAP), the LIDT increased by 240% after combined technique, it demonstrated that combined technique is an effective way to improve the resistance of laser damage of CaF2.
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.
The influence of surface defects on high power laser optical elements will cause some harm to the performances of imaging system, including the energy consumption and the damage of film layer. To further increase surface defects on high power laser optical element, on-machine defects measuring system was investigated. Firstly, the selection and design are completed by the working condition analysis of the on-machine defects detection system. By designing on processing algorithms to realize the classification recognition and evaluation of surface defects. The calibration experiment of the scratch was done by using the self-made standard alignment plate. Finally, the detection and evaluation of surface defects of large diameter semi-cylindrical silicon mirror are realized. The calibration results show that the size deviation is less than 4% that meet the precision requirement of the detection of the defects. Through the detection of images the on-machine defects detection system can realize the accurate identification of surface defects.