Development of an innovative Near-Damage-Free processing technology for High-Power calcium fluoride optical components

Calcium fluoride single crystals (111) exhibit exceptional ultraviolet transparency and resistance to radiation-induced damage. Their uniform refractive index and stable mechanical properties make them highly suitable for next-generation high-power ultraviolet optical components. However, due to their inherent softness and brittleness, coupled with significant anisotropy, calcium fluoride presents unique challenges in material processing and application. Conventional polishing techniques typically result in surface defects such as scratches and microcracks, potentially lowering the resistance of optical components to laser-induced damage. To mitigate these issues, this manuscript introduces an advanced near-damage-free composite processing method that integrates magnetorheological polishing, dynamic acid etching, and ion beam polishing. Separate experiments on magnetorheological polishing and ion beam polishing of calcium fluoride single crystals were performed, focusing on the effects of process parameters on processing quality and mechanisms, followed by process optimization. Subsequently, composite process experiments were verified, using surface Figure accuracy, surface roughness, and photothermal weak absorption intensity as evaluation indicators to quantitatively compare and analyze the performance of the proposed composite processing technique. The results indicate that, compared with single magnetorheological polishing and the ’magnetorheological polishing-ion beam polishing’ process, the composite technique proposed in this study significantly reduces the internal damage of calcium fluoride components, lowering photothermal weak absorption values by 96.77% and 87.14%, respectively. This work provides experimental and theoretical insights and process guidance for fabricating calcium fluoride high-power optical components with lower defect density and improved potential laser damage resistance.