Study of the damage properties of high damage threshold, broadband composite high-reflection thin films at 532 nm

In response to the significant demand for high-damage threshold, broadband high-reflection films for high-power laser systems, composite high-reflection films have been developed. The composite high-reflection films combine the advantages of high-damage threshold materials with the advantages of high-refractive index materials by adding several cycles of high-damage threshold material Al₂O₃/SiO₂ on the surface of traditional Ta₂O₅/SiO₂ high-reflection films. The impact of the number of the Al₂O₃/SiO₂ protective layer cycles on the damage resistance of the composite high-reflection films in the 532nm band is examined. The 1-on-1 laser damage test demonstrated that there was no significant distinction in the laser damage threshold of the composite films with three or six cycles of protective layer. This was primarily due to the presence of various impurities and defects in the films. Six cycles of protective layer protection were found to be more effective. All laser damage of the composite films with six cycles protective layer was observed to occur within the protective layer. Moreover, the interface of Al₂O₃/SiO₂ and Ta₂O₅/SiO₂ was identified as a potential weak region in the composite films. This study provides a valuable reference for the subsequent application of composite dielectric films in high-power laser systems.