Investigation of the high repetition rate picosecond laser induced damage properties of dielectric reflective optical coatings

High repetition rate picosecond laser induced damage properties of Ta2O5/SiO2 dielectric reflective optical coatings were investigated. The laser induced damage was attributed to the increase of the free electron density and temperature enhancement during the irradiation of high repetition rate picosecond laser. The correlation of laser induced damage threshold with pulse numbers was researched. At higher repetition rate, the laser induced damage threshold was reduced more with the increasing of pulsed number. We found that the defects absorption played an important role to the laser induced damage properties of dielectric reflective optical coatings. The damage morphology showed that the evolution of damage site was significantly influenced by the accumulation of laser energy. In order to enhance the resistance capacity, the dielectric reflective optical coatings were annealed with temperature of 260°C. The defect absorption was reduced after the annealing process. For the annealed coating, the laser induced damage threshold under high repetition rate picosecond laser was enhanced as a result of the suppression of defects in the coating.