| Popis: |
Studies were made of the origins of defects in multilayer coatings used as high reflectors in the infrared, with the aim of reducing the numbers of defects and increasing the laser-damage threshold for the coatings. Clean-room conditions were found to be essential for cleaning and coating low-defect substrates. The levels ofsurface and subsurface defects on the substrate were the most important parameters in determining defects on a completed coating. Although the initial chromium film on the silicon substrate appeared to contribute many defects, it was actually making visible submicron defects that were already on the substrates. When the vacuum coating system was operated under clean conditions, the multilayer coatings added few defects to ones already present. Defect densities were reduced by a factor of 100 during the course of the study, resulting in a significant improvement in the laser-damage threshold of the coatings. |
