高功率激光装置光传输管道污染规律及对光学表面损伤性能的影响

研究高功率激光装置光传输管道内部洁净度变化规律,分析其对内部重要光学元件光学性能的影响规律,提出污染控制措施。对光传输管道内部的气溶胶进行采样,并利用空气品质分析仪及扫描电镜对其进行分析,得到光传输管道内部洁净度变化规律和污染源;采用内部放置透射膜元件的方法,研究洁净度等级水平对透射膜的微观结构和透射率的影响,并利用"1-on-1"的测试方式进行透射膜元件的损伤阈值测试。研究结果表明:光传输管道内部的洁净度在激光辐照后迅速上升至万级水平,透射膜元件在此环境下其透过率严重下降,下降幅度为2.5%,且表面微观形貌发生变化。光学透射薄膜表面损伤阈值随表面污染水平呈现线性下降规律,最大下降幅度约为10%。污染监测和成分分析结果表明管道内部灰尘及杂散光或者鬼光束辐照金属产生的等离子体是管道内污染的主要源头,在此基础上提出了正压密封保持的技术手段确保内部光学表面洁净度水平,延长使用寿命。

Contamination in beampath and laser induced damage of optics in high power laser system

To obtain the cleaning methods in high power laser system, the beampath cleanliness experiments and the effects of laser induced damage owing to contamination are studied. The numbers and components of the aerosols are analyzed using the commercial particle counters and SEM. The SiO2 film on K9 is put in the beampath for a certain time, and the transmittance spectra and the morphologies are studied. The laser induced damage threshold of the K9 glass is studied using the 1-on-1 method. The results show that the aerosols keep high concentrations about 7 class after one laser shot with the energy about 5000 J. In this environment, the transmittance of the film descends seriously (about 2.5%), and the aerosols moved onto the surface for clearance in the film. The laser induced damage threshold fluence descends linearly with the cleanliness level of the surface to the maximum decrease of about 10%. The dust and the metal particles are the main contaminations in the beampath, and the source of typical airborne molecular contaminations is discussed and the removal methods are suggested to prolong the life of optics.