Improvement of the bulk laser damage threshold of potassium dihydrogen phosphate crystals by reducing the organic impurities in growth solution

We obtained damage-resistant crystals of potassium dihydrogen phosphate (KDP) by reducing organic impurities in the growth solution. To prevent organic impurity exuded from the wall of the growth vessel, Pyrex glass was used. The residual organic impurities, which mainly derived from KDP raw powder, were reduced by photochemical dissociation using a combination of ultraviolet light and an oxidant (hydrogen peroxide). The resultant total organic carbon of the solution was less than 0.1 ppm. The damage threshold of the crystals grown from this solution was always high (20–22 J/cm2), which is about three times higher than that of crystals grown by conventional methods.