High-power DPL thin films prepared by ion beam sputtering

摘要

Ion beam sputtering enables high laser damage threshold mirrors to be manufactured. Oxygen partial pressure was found to have significant influence on the microstructure and optical properties of HfO_2 thin films deposited by ion beam sputtering (IBS). Atomic force microscopy studies have shown that the surface of single HfO_2 films is clearly characterized by deep holes. When oxygen is excessive, the RMS roughness of the surface increases with the presence of the holes, and the transmittance of the single HfO_2 layers reduces evidently in the shortwave spectral region. The laser-induced damage threshold (LIDT) of HfO_2/SiO_2 multilayer stacks was investigated with a diode pump laser at 1064 nm under a certain repetition frequency. The laser-induced damage morphology of DPL thin films were observed by the optical microscope. SiO_2 overcoats increase the damage threshold and modify the damage morphology of IBS coatings. The LIDT of the cavity mirrors is > 1 GW/cm~2 at 1064 nm (80 ns, 10 KHz).