The sealing cavity materials, such as optical pipelines and support skeletons, will be lightweight, high-strength and corrosion-resistant aluminum alloy materials in high-power pulse laser facilities. Stray light is inevitable due to surface scattering of optical components and residual reflection in the film layer. However, after the stray light continuously irradiates the surface of the sealed cavity, trace contaminants are deposited on the surface of the optical components, intensifying the damage of the optical components. To control the clean environment and the damage caused by optical component contamination in high-energy laser facilities, in our study, we first measured the damage threshold of aluminum alloy 5A06A at fundamental frequency laser (λ=1064 nm). We determined that the damage threshold of aluminum alloy was about 50 mJ/cm² by plasma flash method. The cleaned aluminum alloy and the 45° reflection mirror were placed in a sealed chamber to simulate the residual stray light reflected by the actual high-energy laser. The measurement results showed that the laser-induced damage threshold of the 45° reflection mirror was reduced by ~60% by the 1-on-1 measurement method, and a large number of flocculent organic contaminants clusters were found by the scanning electron microscope and energy dispersive spectrometer. Therefore, we speculate that these organic contaminants may come from the machining process of aluminum alloy surface residual cutting fluid under intense laser irradiation. The results of this study point out one of the important sources of contaminants in high-power pulsed laser facilities and provide an important basis for proposing an appropriate and effective cleaning strategy.

stray light,optical components,aluminum alloy,contaminants