The rapid growth of large-scale KDP single crystal in brief procedure

Potassium dihydrogen phosphate (KDP) is the necessary nonlinear optical material used to convert laser light to shorter wavelengths for laser fusion experiment. Large bulk KDP crystals, usually with sizes up to 55×55cm2 so as to make the frequency doubler designed at cross section 43×43cm2 for the facility requirement loading highly flux of power laser, were grown rapidly in a Holden-type crystallizer by the temperature reduction method. Pure water and KDP raw material with few ion impurities, such as Fe, Cr and Al less than 0.5ppm, were used. The growth procedure provided briefly here started from inserting the point seed on crystallizer in overheated solution and programmed at temperature 60–35°C, growth rate 5–15mm/day, proper rotation of about 10–15rpm, 80–100 days required for rapid growth that would produce large, transparent and above 300kg weight single crystals. Growth parameters for stable growth are summarized; the most significant one for growing large KDP crystals is the assurance of solute transportation at prism face. The disturbance of irregular solution flow could easily cause inclusions near the edge area of pyramid or prism face. The optical transmission, light scattering and laser damage threshold of crystals were determined.