Damage mechanisms for KTiOPO 4 crystals under irradiation of a cw argon laser

Abstract

We have developed a simple method for measuring damage threshold of KTP crystal for CW irradiation using an Argon laser. The experimental results show that there are two types of optical damage in KTP crystal depending on the polarization of the incident laser beam. One type of optical damage corresponds to gray tracks that will be formed when the polarization is perpendicular to the z-axis. Another one is invisible damage that will be formed when the polarization is parallel to the z-axis. In addition, we also observed photorefractive two-wave mixing in KTP crystal under each of the above two polarization states. Our experimental results imply that there exists charge drift during the process of optical damage at both of these polarization states, but the mechanisms are different at these two orthogonal polarization states. After analyses, we believe the first type of damage is due to the formation of Ti 3+ centers and the second one is due to the drift of K + ions.