Control of gray-tracking formation in KTiOPO/sub 4/ crystals by thermal annealing preprocess

Summary form only given. The KTiOPO/sub 4/ (KTP) crystal was used for second-harmonic generation (SHG) of high-average-power lasers because it has a large nonlinear optical coefficient and a wide temperature bandwidth. However, the crystal has one disadvantage, i.e., gray-tracking formation. The gray-tracking was investigated by many workers. The gray-tracking susceptibility (GTS) was different for individual crystal. To understand the gray-tracking formation, many crystals from different growth techniques should be compared. Relationship between the absorption coefficient and the GTS or the impurities for different KTP crystals was investigated. Finally, we propose a new approach to improve the gray-tracking.