CHARGE TRANSPORT PROCESSES IN LINBO3FE AT HIGH-INTENSITY LASER-PULSES

Light-induced refractive index changes in LiNbO3 : Fe crystals are investigated at high light intensities (> 10(9) W m-2). Holographic gratings are recorded and erased with frequency-doubled pulses of a Q-switched Nd : YAG laser. We find new intensity dependent contributions to the holographic sensitivity, to the photoconductivity, and to the saturation value of refractive index change. Light-induced absorption changes are also detected. These results indicate that the Fe2+/Fe3+ charge transport model, well established for low intensities, has to be modified for high intensities by assuming additional centers which trap and supply electrons.