The axial temperature distribution in an empty crucible and the determination of quenched interface within fixed crucible were investigated to find the relationships governing the growing process of CaFz by Bridgman-Stockbarger methods. A system of additional molybdenum reflective sheaths was placed into the furnace unit and its effect on the temperature field was estimated in order to achieve the growth optimum. A long liner into the diaphragm bore of the furnace and a number of thin rings slipped on the crucible stem were found capable to provide a reproducible optimum on each stage of growing in single and multicamera crucibles at a relatively low level of power supply. Single and ingroup growth experiments were carried out using high density quenched ingots purified from oxygen contaminants through high temperature treatment of fluorspar. The properties of the grown crystals were found to depend on the degree of the fluorspar purification and on the improvement of the thermal conditions yielding either competitor or laser-grade CaF2. In multicamera crucibles the crystals grown in the cent!ral compartment are of better characteristics than those in the peripheral ones.
Optical properties of CaF2, grown by a controlled Bridgman–Stockbarger technique, are studied by CuBr and SrBr2 vapour lasers. Absorption losses are determined as a function of the grown crystal volume, the crystallization front (CF), and the real crystallization rate. It is found that the absorption losses are relatively independent of the transmitted wavelengths in a wide spectral range from the deep ultraviolet (DUV) to the middle infrared (MIR) spectral region and their minimum corresponds to CF positions within the upper half of the adiabatic furnace zone, where the CR reaches a constant value slightly higher than the speed of crucible movement. The crystal quality conforms to laser grade CaF2 for the DUV, visible and MIR spectral regions and may be controlled efficiently by introducing an appropriate systematic correction in the furnace temperature field, which shifts the CF position.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.