Growth of optical quality langasite crystal

La3Ga5Si14 (LGS) is a congruently-melt crystal and can be grown with Czochralski method. The growth conditions for LGS crystals are carefully investigated. Optical quality (instead of piezoelectric quality) LGS crystals with the size larger than 50 mm have been grown. And these crystals are suitable for use of EO Q-switch. By X-ray topography, together with optical microscopic observations for LGS samples, the core part of the as-grown crystal was determined as a collection of band of dislocations.