Fabrication of ultra-low-absorption thin films via ion beam-assisted electron-beam evaporation

Abstract High-power laser systems require thin films with extremely low absorption. Ultra-low-absorption films are often fabricated via ion beam sputtering, which is costly and slow. This study analyzes the impact of doping titanium and annealing on the absorption characteristics of thin films, focusing on composition and structure. The results indicate that the primary factor influencing absorption is composition. Suppressing the presence of electrons or holes that do not form stable chemical bonds can significantly reduce absorption; for amorphous thin films, the structural influence on absorption is relatively minor. Thus, composition control is crucial for fabricating ultra-low-absorption films, while the deposition method is secondary. Ion beam-assisted electron-beam evaporation, which is relatively seldom used for fabricating low-absorption films, was employed to produce high-reflectivity films. After annealing, the absorption at 1064 nm reached 1.70 parts per million. This method offers a cost-effective and rapid approach for fabricating ultra-low-absorption films.