Influencing factors in the laser-induced damage threshold of Ta2O5 films prepared with different methods

Ta2O5 films were prepared by electron beam evaporation (EBE), ion-beam sputtering (IBS) and sol-gel methods, respectively. It showed that both the refractive indices and the surface roughness of the films were very relevant to the preparation methods. The laser-induced damaged threshold (LIDT) at 1064 nm and 12 ns of the EBE, IBS and sol-gel films was 8,3, 14.4 and 19.6 J/cm(2), respectively. Although the damage of all the films was initiated from defects, the EBE and IBS films presented the thermal melt damage feature, whereas the sol-gel film showed the damage feature of interaction between thermal melt and stress. The impurity defects and structural defects were the main influencing factors in the LIDT of the EBE and IBS films. For the sol-gel film, not only the defect but also the special structure affected the laser damage resistance. The highest LIDT achieved by the sol-gel film was attributed to the least defects and the network structure.