Beam-size effects on the measurement of sub-picosecond intrinsic laser induced damage threshold of dielectric oxide coatings

Laser-induced damage experiments on H f O 2 and N b 2 O 5 hin films were performed with 500 fs pulse duration at 1030 nm wavelength. Threshold fluences as a function of beam size have been determined for effective beam diameters ranging from 40 to 220 µm, in a single shot regime. The results suggest no beam-size effect related to material properties in the investigated range, but size effects related to the metrology. The results indicate the importance of appropriate focusing conditions and beam measurement to qualify the optics for use in lasers with large beam sizes.