Advanced Mode Control and High-Power Optics Technology. Volume 2. Halide Window Materials Technology

Abstract : The results reported here represent significant advances in the state of the art of high-power laser windows and coatings. An order-of-magnitude improvement was achieved in the material parameters of single crystal KCl over the values which characterized the best available materials at the beginning of the study. The RAP technique, involving processing under an atmosphere of He + CCl4, was used for window materials purification, crystal growth, and for surface layer exchange in KCl crystals. It led to the development of a one-step processing for KCl crystal growth, from powder to crystal, which minimizes the incorporation of OH(-) in the KCl crystals. Optical, mechanical, and surface stability evaluations of various fluoride and chloride crystals are also reported. The coating program goal, which was to achieve 0.1% or less absorption per coated window surface at 10.6 micrometers, has been demonstrated for some of the optical coatings prepared during the program. Theoretical designs and experimental results for coatings for alkali halides, zinc selenide, and cadmium telluride are presented with emphasis placed on coatings for KCl.