Kyropoulos growth of a 300-g SrB₄O₇ single crystal using a twin-type stirring blade

Abstract We report the successful Kyropoulos growth of a large strontium tetraborate (SrB 4 O 7 , SBO) single crystal that weighs more than 300 g. In order to grow the large and transparent crystal, a new twin-type stirring blade was used along with a 150-mm-diameter crucible. The use of the stirring blade results in the production of the world’s largest SBO crystal with dimensions of 100 mm (a) × 30 mm (b) × 32 mm (c), a weight of 328.2 g, and a wide transparency down to 130 nm. These results will then lead to the development of large SBO crystals as optical window materials for high-power DUV laser processing systems.