Annealing effects on structural, optical properties and laser-induced damage threshold of MgF₂ thin films

The chemical structures, optical properties and laser-induced damage thresholds of magnesium fluoride films annealed at different temperatures were investigated. The results showed that the stoichiometry of MgF₂ film changed a little with the increase in annealing temperature. Analysis of the optical properties indicated that excellent antireflection behavior of the film in the range of 200-400 nm can be obtained by the samples coated with MgF₂ film. The refractive index increased and the extinction coefficient decreased with increasing annealing temperature. Compared with the as-deposited films, the laser-induced damage threshold was improved after annealing process and decreased with the increase in annealing temperature, which was probably due to the denser film and more absorption centers under higher annealing temperature.