| Summary: | In order to obtain the relationship between the properties and the oxygen flow rate of La _2 Ti _2 O _7−x film, the films were prepared by electron beam evaporation with various oxygen flow rates on Si and quartz substrates. The effects of oxygen flow on the properties of La _2 Ti _2 O _7−x film were analyzed by XRD, XPS, optical constant and laser damage test. The result shows that the La _2 Ti _2 O _7−x film lose oxygen and lead to the transition of Ti ^4+ to Ti ^3+ in oxygen-free environment. When the oxygen flow rate is greater than 4 sccm, the content of Ti ^4+ is stable. The refractive index of La _2 Ti _2 O _7−x films decreases with the increase of oxygen flow rate and stabilizes at oxygen flow rate greater than 4 sccm. The extinction coefficient of film deposited in oxygen-free environment is less than 10 ^−4 . As the oxygen flow rate increases, the film absorption is further improved to reach 10 ^−5 at wavelengths longer than 350 nm. The laser damage threshold of films increased with increasing oxygen flow and the maximum value is 18.35 J cm ^−2 .
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