Holographic and electric investigations of KTiOPO/sub 4/ crystals used for second harmonic generation

Summary form only given. We present our experimental results of the investigations of KTP crystals with respect to their photorefractive behavior using holographic and electric methods. Holographic experiments were performed in the infrared spectral range using 180/spl deg/ reflection geometry to simulate the intracavity transmission of the harmonic lightwaves through the crystal. In this geometry a sinusoidal intensity modulation is produced parallel to the wave vectors. Since light illumination leads to an increase of the temperature due to absorption processes, there is a sinusoidal modulation of the temperature parallel to the wavevector of the transmitting beams and a gaussian distribution of the temperature parallel to the polar axis. Measurements of the conductivity show, that an increase of the temperature leads to an increase of the ionic conductivity of the K/sup +/-ions, which reaches values up to 10/sup -4/ /spl Omega//sup -1/ m/sup -1/ parallel to the crystallographic c-axes. Therefore, it is possible to transfer the modulation of the temperature in a modulation of the K/sup +/-ions, which changes the refractive index. We discuss the transport mechanism, which is responsible for the migration of the K/sup +/-ions in this model.