High-repetition rate picosecond laser-induced damage properties of Ta2O5:SiO2 coatings

High-repetition rate laser-induced damage of Ta2O5:SiO2 coatings was investigated at 355 nm wavelength and a repetition rate of 30 kHz. Laser-induced damage thresholds of coatings with different mixture ratios were measured. The relationships between laser-induced damage threshold and the material band gap and defect absorption were analyzed. Laser-induced damage threshold decreased with increase in number of laser pulses owing to enhancement of the absorption. Enhancement of absorption is attributed to the increase in density of mid-state defects induced by the picosecond laser pulses. The relationship between mid-state defects and the material mixture ratio was also analyzed.