The Damage Threshold of Multilayer Film Induced by Femtosecond and Picosecond Laser Pulses

Laser-induced damage threshold (LIDT) is an essential factor in measuring the anti-laser damage of optical films. The damage threshold and morphology of the Ta2O5/SiO2 multilayer film prepared by electron beam evaporation were studied by femtosecond (50 fs) and picosecond (30 ps) laser irradiations. The results showed that the LIDT of the film was 1.7 J·cm−2 under the femtosecond laser. The damage morphology developed from surface damage to a clear layered structure, and the outline has become more transparent and regular with an increase in the laser fluence. Under the picosecond laser irradiation, the LIDT of the film was 2.0 J·cm−2. The damage morphology developed from small range to thin film layer separation, and the outline changed from blurry to clear with an increase in laser fluence. Therefore, the LIDT of the film decreased with a decrease in the laser pulse width.