OPTICAL DAMAGE IN FE-DOPED LINBO3

The origin of the internal drift field, which plays an important role in the process of optical damage in LiNbO3, has been discussed. The refractive index change in Fe-doped LiNbO3 increases linearly with increasing intensity of He–Ne laser, being followed by saturation. The rise time and the magnitude of the refractive index change due to optical damage decrease with increasing temperature. The decay time of optical damage also decreases with increasing temperature. These experimental results are explained satisfactorily in terms of the bulk photovoltaic effect due to the transition from impurity level to conduction band proposed by Glass et al. However, the existence of the inherent built-in internal field cannot be completely denied at this stage, because band to band transition by X-ray irradiation also induces optical damage in LiNbO3. © 1979 The Japan Society of Applied Physics.