Materials for High-Power Laser Applications: Point Defects in KTP and ZnGeP2

摘要

The operation of devices utilizing nonlinear optical materials such as KTP andZnGeP2 are limited at high laser power by point defects in the crystal. This project has used electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) experimental techniques to identify and characterize the primary point defects in KTP, ZnGeP2, and CdGeAs2 crystals. In KTP, the primary electron trap (i.e., a Ti3+ ion) is associated with the formation of gray tracks. The present investigation has shown that these Ti3 ions have a significantly different local environment depending on whether the crystal was grown hydrothermally or by the flux technique. Also, in KTP, it is shown that potassium vacancies are the primary hole trapping site at low temperature. The acceptor in as-grown crystals of ZnGeP2 is shown to be a singly ionized zinc vacancy or a zinc ion on a germanium site. Results in CdGeAs2 suggest that the dominant EPR-active defects are either a cation vacancy or a cation antisite. jg.