Laser Damage Mechanisms of Amorphous Ta₂O₅ Films at 1064, 532 and 355nm in One-on-One Regime

Ta₂O₅ films are deposited on fused silica substrates by conventional e−beam evaporation. Surface topography and chemical composition are examined by atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). The calculation of electron structures of Ta₂O₅ and Ta₂O_5−x is attempted using a first-principle pseudopotential method within the local density approximation. The laser-induced damage threshold (LIDT) is performed at 1064, 532 and 355 nm in 1-on-1 regime, respectively. The results show that the LIDT increases with the wavelength increasing, which is in agreement with the wavelength effect. However, the LIDT results are not consistent with the empirical equation (I(λ)=aλ^m), which may be attributed to the intrinsic absorption of Ta₂O₅ at the wavelengths of 532 or/and 355 nm. Moreover, different damage morphologies are observed when the films are irradiated at different wavelengths. It is concluded that the laser damage at 1064 nm is the defect dominant mechanism and at 355 nm it is the intrinsic absorption dominant mechanism, whereas at 532 nm it is the combined defect and intrinsic absorption dominant mechanism.