Crystal Growth Of Optical Materials By The Gradient Solidification Method

Large, high quality, single crystals of sapphire and calcium fluoride are routinely grown at the NRCN laboratories via the Gradient Solidification Method (GSM). This method was initially developed for the growth of dome-shaped sapphire crystals and then also applied to the production of bulk cylindrical crystalline boules. The diameters of the currently grown crystals are 150 mm and 85 mm for the sapphire and calcium fluoride respectively. The development of growth procedures for larger diameter sapphire crystals (up to 12") is underway. The growth processes were investigated and crystal imperfections (i.e. grain boundaries, twins, scattering centers, etc.) were correlated with various growth conditions. The optical and mechanical properties of the grown crystals were measured on fabricated components.