Damage resistance and crystal growth of KDP

An investigation is reported of the dependence of laser-damage site density on fluence and on various parameters of crystal growth and post-growth treatment. Damage site density (number of defects per unit volume) was found to increase monotonically with fluence (for single 1-ns pulses of 1.06 μm laser light). Site density (at a fluence of 10 J/cm/sup 2/) was influenced by solution flow rate, seed defect removal prior to growth, quaternary ammonium cations, and thermal cycling following growth. No dependence of damage susceptibility on growth rate was found over the range 3-30 mm/d. A model is presented which postulates the electrostatic adsorption of organic material onto the growing crystal surface and subsequent inclusion into the crystal. According to the model, damage occurs by absorption of light by inclusions of solution-wetted organic debris, resulting in pressure increase and hydraulic fracture of the surrounding crystal