Method for making large-volume CaF2 single cystals with reduced scattering and improved laser stability, the crystals made by the method and uses thereof

摘要

The method provides CaF₂ single crystals with low scattering, small refractive index differences and few small angle grain boundaries, which can be tempered at elevated temperatures. In the method a CaF₂ starting material is heat-treated for at least five hours at temperatures between 1000° C. and 1250° C. and then vaporized at a temperature of at least 1100° C. in a vacuum of at most 5*10^-4 mbar to form a vapor. The vapor is condensed at a temperature between 500° C. to 1280° C. to form a condensate. Then a melt formed from the condensate is cooled in a controlled manner to obtain the single crystal, which is subsequently tempered. The method is preferably performed with a CaF₂ starting material including waste material and cuttings from previously used melts.