GROWTH AND OPTICAL CHARACTERIZATION OF LARGE POTASSIUM TITANYL PHOSPHATE CRYSTALS

Potassium titanyl phosphate (KTP) crystals were grown from the K6P4O13 (K6) flux using a temperature falling method. Real-time mesurement of the weight of the crystal during the growth was carried out with an electronic load cell in order to estimate the bulk growth rate. It was found that the growth rate of the crystal became too fast and liquid that inclusions were formed during a certain growth term in the growth period by excessively high supersaturation when the temperature falling rate was constant. In order to avoid this process, by changing the temperature cooling rate, a KTP crystal, 32 X 42 X 87 mm (a X b X c) without liquid inclusion was successfully obtained. The refractive indices, which were measured by means of laser interferometry, were found to be varying along the growth direction. Variation of the refractive indices was approximately 1.6 X 10(-4) for n(z) and 7.1 X 10(-6) for n(xy), giving rise to a change of the phase matching direction of up to 0.38-degrees.