Abstract
Hafnia and yttria films for optical applications were prepared by pulsed laser ablation with oxygen ion bombardment of the growing films. The influence of the laser and ion beam parameters on the refractive index and microstructure of the films was investigated. The optical quality of the films with respect to absorption and laser damage was characterized at the Nd:YAG-laser wavelength by measuring the laterally resolved absorptivity and the laser damage thresholds. Both hafnia and yttria films prepared at low ion energy and intensity (150 eV, 50 μA/cm 2) were amorphous and had a high bulk-like refractive index and packing density. At high ion energy and intensity (700 eV, 400 μA/cm 2) the films became polycrystalline with high refractive index and packing density at relatively high growth rates above 10 to 20 nm/min or relatively low refractive index and packing density at low growth rates. Films with high laser damage threshold at 1.06 μm wavelength could only be prepared with strong oxygen bombardment. Highly reflective multilayer systems of only one material with alternately high and low refractive index were prepared by varying the parameters of oxygen ion bombardment during deposition. Their reflectivity and laser damage threshold at 1.06 μm as well as their microstructure were investigated.
Published Version
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