Laser damage properties of TiO2/Al2O3 thin films grown by atomic layer deposition.

Research on thin film deposited by atomic layer deposition (ALD) for laser damage resistance is rare. In this paper, it has been used to deposit TiO(2)/Al(2)O(3) films at 110 °C and 280 °C on fused silica and BK7 substrates. Microstructure of the thin films was investigated by x-ray diffraction. The laser-induced damage threshold (LIDT) of samples was measured by a damage test system. Damage morphology was studied under a Nomarski differential interference contrast microscope and further checked under an atomic force microscope. Multilayers deposited at different temperatures were compared. The results show that the films deposited by ALD had better uniformity and transmission; in this paper, the uniformity is better than 99% over 100 mm Φ samples, and the transmission is more than 99.8% at 1064 nm. Deposition temperature affects the deposition rate and the thin film microstructure and further influences the LIDT of the thin films. As to the TiO(2)/Al(2)O(3) films, the LIDTs were 6.73±0.47 J/cm(2) and 6.5±0.46 J/cm(2) at 110 °C on fused silica and BK7 substrates, respectively. The LIDTs at 11 °C are notably better than 280 °C.