Optical properties and laser-induced damage threshold of Ta<inf>2</inf>O<inf>5</inf> films deposited by different methods

采用电子束蒸发(EBE)和离子束溅射(IBS)制备了不同的Ta_2O_5薄膜,同时对电子束蒸发制备的薄膜进行了退火处理。研究了制备的Ta_2O_5薄膜的光学性能、激光损伤阈值(LIDT)、吸收、散射、粗糙度、微缺陷密度和杂质含量。结果表明,退火可使电子束蒸发制备的薄膜的光学性能得到改善,接近离子束溅射的薄膜的光学性能。电子束蒸发制备的薄膜的损伤阈值较低的主要原因在于吸收大,微缺陷密度和杂质含量高,而与薄膜的散射和粗糙度关系不大。退火后薄膜的吸收和微缺陷密度都明显降低,损伤阈值得到提高。退火后的薄膜损伤阈值仍然低于溅射得到的薄膜损伤阈值是因为退火并不能降低膜内的杂质含量,因此选用高纯度的蒸发膜料和减少电子束蒸发过程中的污染有可能进一步提高薄膜的损伤阈值。Ta<inf>2</inf>O<inf>5</inf> films were prepared on BK7 substrates using electron-beam evaporation (EBE) and ion-beam sputtering (IBS), and the films deposited by EBE were also annealed. The optical properties, laser-induced damage threshold (LIDT), absorption, scattering and root-mean square (RMS) roughness, microdefect density and impurity content of the prepared films were investigated. The results show that the optical properties of the annealed Ta<inf>2</inf>O<inf>5</inf> films deposited by EBE can be improved near to that by IBS. The LIDT of Ta<inf>2</inf>O<inf>5</inf> films deposited by EBE is lower than that by IBS, which is due to the larger absorption, microdefect density and impurity content and has nothing with the scattering and RMS roughness. The films prepared by EBE after being annealed show lower absorption and microdefect density, and improved LIDT. The LIDT after being annealed is still lower than that by IBS, which can be attributed to that the annealing cannot decrease the impurity content of the films. Therefore, the higher LIDT would be achieved by using high purity starting material and reducing the contaminant in the evaporation course