Effects of deposition parameters on laser-induced damage threshold of Ta2O5 films

Ta₂O₅ films were deposited on BK7 substrates by e-beam evaporation with different deposition parameters such as substrate temperature (323-623 K), oxygen pressure (0.5-3.0×10⁻² Pa) and deposition rate (0.2-0.5 nm/s). Absorption, scattering and chemical composition were investigated by surface thermal lensing (STL) technique, total integrated scattering (TIS) measurement and X-ray photoelectron spectroscopy (XPS), respectively. The laser-induced damage threshold (LIDT) was assessed using pulsed Nd:YAG 1064 nm laser at a pulse length of 12 ns. The results showed that optical properties, absorption and LIDT were influenced by the deposition parameters and annealing. However, scattering was little correlated with the deposition parameters. On the whole, the LIDT increased with increasing substrate temperature and oxygen pressure, whereas it increased firstly and then decreased upon increasing deposition rate. After annealing at 673 K for 12 h, the LIDT of films improved significantly. The dependence of possible damage mechanism on deposition parameters was discussed.