PROPERTIES OF PULSED-LASER DEPOSITED OPTICAL COATINGS

Hafnia and yttria films for optical applications were prepared by puls ed laser ablation with oxygen ion bombardment of the growing films. Th e influence of the laser and ion beam parameters on the refractive ind ex and microstructure of the films was investigated. The optical quali ty of the films with respect to absorption and laser damage was charac terized at the Nd:YAG-laser wavelength by measuring the laterally reso lved absorptivity and the laser damage thresholds. Both hafnia and ytt ria films prepared at low ion energy and intensity (150 eV, 50 mu A/cm (2)) were amorphous and had a high bulk-like refractive index and pack ing density. At high ion energy and intensity (700 eV, 400 mu A/cm(2)) the films became polycrystalline with high refractive index and packi ng density at relatively high growth rates above 10 to 20 nm/min or re latively low refractive index and packing density at low growth rates. Films with high laser damage threshold at 1.06 mu m wavelength could only be prepared with strong oxygen bombardment. Highly reflective mul tilayer systems of only one material with alternately high and low ref ractive index were prepared by varying the parameters of oxygen ion bo mbardment during deposition. Their reflectivity and laser damage thres hold at 1.06 mu m as well as their microstructure were investigated.