Gray tracks in KTiOPO4: Mechanism of creation and bleaching

Abstract This study investigated the possible mechanisms of the KTP gray tracking (GT). Optical, electrical and luminescence spectroscopy techniques were used in a wide temperature range. As both laser and ionising emission create similar damage in KTP crystals, we used X-ray irradiation to model the GT coloration of KTP. For the first time, low-temperature spectra of the irradiation-induced absorption have been measured in the temperature range of 80–295 K. Kinetics of damage accumulation and bleaching have been investigated. Two stages of coloration, recharging of preradiational defects and creation of new radiation defects, have been found and studied at different temperatures. The temperature dependence of the coloration rate is rather strong and inolves at least two different mechanisms. Ionic conductivity and dielectric losses have been studied in the 20–200 kHz frequency range at temperatures up to 700 K. The essential role of ionic processes in coloration-decoloration of KTP has been shown. A possible mechanism of the GT damage is proposed.