Optimization of HfO2, Al2O3 and SiO2 deposition leading to advanced UV optical coatings with low extinction

The performance of optical coatings for UV region (200-300 nm) is closely related to their optical losses. There are a few factors which significantly influence the extinction of deposited coating - deposition vacuum, contamination from filaments of e-beam guns, ion source and finally, the optical properties of selected deposition materials. In this work the contribution of these different factors was investigated and evaluated. HfO2, Al2O3 and SiO2 are the most widely used materials for producing UV optical coatings down to 200 nm. Influence of background oxygen pressure during HfO2 and Al2O3 deposition was evaluated which enabled to reduce extinction of the deposited UV optical coatings.