OPTICAL AND MICROSTRUCTURAL PROPERTIES OF LASER-PULSE DEPOSITED OXIDE-FILMS

HfO2 and Y2O3 films for optical applications are prepared by excimer l aser ablation and CO2 TEA laser evaporation, respectively. The growing films are bombarded with oxygen ions of 150 to 550 eV energy and seve ral 10 to 250 muA/cm2 ion current density. Films of both materials dep osited at relatively low ion bombardment possess high refractive index es approaching those of the corresponding bulk. These films are of amo rphous structure and have a high packing density with low porosity. In creasing ion bombardment, i.e. increasing ion energy and current densi ty, leads to a marked decrease in refractive index and hence in the pa cking density due to increasing crystallization within the films. In t he case of hafnia, for example, the refractive index at 600 nm wavelen gth decreases from 2.15 down to 1.80. Using appropriate deposition par ameters hafnia and yttria films, with both high and low refractive ind ex, showing low absorption and high laser damage thresholds at 1.06 mu m wavelength can be prepared.