Effects of different post-treatment methods on optical properties, absorption and nanosecond laser-induced damage threshold of Ta2O5 films

• Different post-treatment methods were adopted to improve film properties.
• Laser conditioning after annealing obtained the highest laser damage resistance.
• A model was proposed to reveal defect evolution in films.

Ta2O5 films deposited by ion beam sputtering were post-treated with different methods. The optical properties, microstructures, surface morphologies, absorption and laser-induced damage threshold (LIDT) at 1064 nm and 12 ns of the films were comparatively studied. Annealing conduced to larger changes of optical transmittance and surface morphologies whereas it led to smaller changes of absorption and LIDT than laser conditioning. As it was shown, all the three post-treatment methods in this study were beneficial to the laser damage resistance of the films, yet the details of the defect elimination caused by these methods were different. A defect evolution model was proposed, which revealed the different effects of post-treatment methods on the defect repair of the films. The highest LIDT achieved by the combination of annealing and laser conditioning was due to their complementary effect which resulted in the lowest defect density and the smallest defect size of the film.