The diameter of a crystal growing in a Czochralski apparatus is maintained constant by automatically adjusting the temperature of the melt. Information concerning the instantaneous crystal size is derived from the reflection of a vertically incident laser beam on the free melt surface which, due to the surface tension, is distorted near the growing crystal. The system has been tested by growing KCl and Bi1 2GeO2 0. The crystal diameter was maintained to within 1%. © 1972.
Gross, U., & Kersten, R. (1972). Automatic crystal pulling with optical diameter control using a laser beam. Journal of Crystal Growth, 15(2), 85–88. https://doi.org/10.1016/0022-0248(72)90127-3