The effect of deposition temperature on the properties of 355-nm high-reflectivity (HR) coatings was investigated. A series of 355-nm HR coatings were deposited by electron-beam evaporation using the same deposition process, but different deposition temperatures: 200, 250, 280, and 320 °C. Transmittance and high reflectance of the samples were measured with a Lambda 900 spectrometer, and the highest reflectance, 98.7%, was achieved at a deposition temperature of 280 °C. The laser-induced damage threshold (LIDT) was measured with a 355-nm pulsed laser with a pulse width of 8 ns. It was found that the deposition temperature had a significant effect on the LIDT of coatings. LIDTs up to 18.5 J/cm2 were achieved when the deposition temperature was 280 °C. The LIDT of the coating deposited at 280 °C is about three times greater than that of coatings deposited at the other temperatures. Damage morphologies of samples at different deposition temperatures were observed with a Leica-DMRXE microscope. Microstructures of the samples were characterized by x-ray diffraction (XRD). An absorptance-dominated model is proposed, which agrees very well with the damage threshold results.
Zirconium oxide films were prepared with and without ion beam assisted deposition (IBAD) by an electron beam. The effects of Ar-ion bombardment on the optical inhomogeneity of ZrO<sub>2</sub> films deposited at room temperature were investigated. The results show that all samples are amorphous, and the refractive index of sample A without IBAD randomly changed with the film thickness, while the relative inhomogeneity of samples B, C, D with IBAD nearly zero. It was found that the energy of depositing molecule or atom had an important effect on the optical inhomogeneity of films, and the optical inhomogeneity of amorphous ZrO2 films could be improved by IBAD.
The ion cleaning effect on the roughness of substrates and laser induced damage thresholds (LIDT) of films were investigated. It is found that ion cleaning has different effects on the roughness of substrates with the different ion cleaning time, and it improves the LIDT of single layer films greatly.
Laser-induced damage threshold (LIDT) of 355nm was a more severe problem than that of 1064nm. This work had been carried out to obtain high LIDT and high reflectance for Al<sub>2</sub>O<sub>3</sub>/MgF<sub>2</sub> quarter wave multilayer stacks (35 layers). All the samples were deposited by electron beam evaporation using the same deposition process at different deposition temperatures. LIDT was measured by using a 355 nm Nd:YAG pulsed laser with a pulse width of 8 ns. It was found that deposition temperature had a fundamental effect on the thresholds of HR coatings. LIDT up to 18.5J/cm<sup>2</sup> was achieved when the deposition temperature was 280°C. Transmittance and high reflectance of the samples were measured by Lambda 900 Spectrophotometer and the high reflectance of 98.7% was achieved. An absorption dominated model was proposed which met the results of damage thresholds.