Effect of oxygen vacancies on the laser-induced damage resistance of Y_026Hf_074O_x thin films

The influence of the oxygen sub-stoichiometry on the femtosecond laser-induced damage resistance of Y0.26Hf0.74Ox films was investigated in this work. Photoluminescence (PL) spectroscopy was applied to analyze the various states of oxygen vacancies (VO), and laser-induced damage measurement was performed using a single 500 fs pulse laser at a wavelength of 1030 nm. Based on the PL spectra, a probable band gap structure with different defect energy levels was obtained, which is significant in explaining an observed inverse correlation between the laser-induced damage threshold (LIDT) and the concentration of VO. The crystallization and the refractive index, which were previously found to be crucial factors in laser-induced damage resistance of optical thin films, are also closely dependent on the amount of induced oxygen vacancies.