1064 nm laser conditioning effect of HfO2/SiO2 high reflectors deposited by E-beam

Laser conditioning is one of the important methods to improve the laser damage threshold of film optics. First, both 1-on-1 and R-on-1 test are done on the fundamental frequency high reflectors, which are evaporated from hafnia and silica by e-beam. Next, the typical damage morphologies occurred in the two measurements are compared and analyzed. Obvious laser conditioning effect is observed in the R-on-1 test, the damage threshold of which is three times larger than that of 1-on-1 test. The typical morphology in 1-on-1 test is plasma scalding with a central flat-bottom pit and the typical morphology in R-on-1 test is plasma scalding only. The results of surface profiler measurement show that all the centers of the plasma scalds that occurred in the above two typical damage morphologies are raised. The two different damage morphologies imply that absorbing defect is the inducement of the damage and the macroscopical reason for the improved laser damage threshold in R-on-1 test, is presented as the mechanic stability of absorbing defects.