Gray track susceptibility and stoichiometry of KTP crystals

Summary form only given. When used for SHG of 1064 nm radiation or in OPO pumped at 532 nm, KTP crystals frequently display gray tracks. The origin of the effect is far from being understood completely. A unique photothermal common-path interferometer has been used to observe the gray track damage in KTP. CW green laser radiation energy flux was up to 200 kW/cm/sup 2/. Gray track build-up has been monitored at 1064 nm. Temporal and spatial dynamics of the gray track formation have been investigated in more detail than previously reported. Useful criteria for quantitative evaluation of KTP gray track susceptibility have been developed. The data obtained in gray-track experiments have been used as a feedback to modify in a desirable way the KTP growth process. We report the first experimental evidence that the gray track susceptibility of KTP depends on the material nonstoichiometry similarly to the material Curie temperature and electrical conductivity as reported earlier. We observed that the gray track susceptibility of the flux-grown KTP could be significantly decreased by adjustment of the growth parameters, such as growth temperature and/or potassium concentration in flux.