KTiOPO4 (KTP) is a key material for nonlinear optical and electro-optical applications. However, many applications have been limited by laser-induced absorption, commonly referred to as "grey tracking". While significant improvements have been made in the damage resistance of KTP, many users still report laser induced damage in high average power, high repetition rate or continuous wave applications. Recently advances have been made in the understanding of laser induced gray tracking in KTP; improvements in crystal growth processes; and control of KTP defects and stoichiometry. The results of the Phase I program clearly demonstrated that by suitable processing, KTP crystals with significant improvement in laser damage susceptibility can be produced. Changes in solution chemistry coupled with implementation of new growth techniques produced KTP - now designed KTP-UGTR, that is superior to currently available commercial material. There remains two (2) problems to overcome; growth stria and crystal cracking. We propose to solve these by application of techniques developed for KTP. A complete understanding of the relationship between laser damage, crystalline defects, stoichiometry, and crystal growth will allow for the development of a routine, production process that continuously yields low susceptibility, high optical quality crystals. With the recent advances in diode pumped, Q-Switched solid state laser sources, there is an increasing need for second harmonic doubling crystals which can withstand the associated peak powers and high repetition rates. This is particularly true of the new generation of green surgical lasers.
Keywords: KTP KTIOPO4 CRYSTAL GROWTH GRAY TRACKS LASER INDUCED DAMAGE SECOND HARMONIC GENERATION
