Understanding light intensity thresholds for catastrophic optical damage in LiNbO3

The appearance of light intensity thresholds for catastrophic optical damage in LiNbO3 is satisfactorily explained by using a photorefractive model based on the Fe2+<-> Fe3+ and Nb-Li(4+)<-> Nb-Li(5+) defect pairs. Model simulations of the photorefractive amplification gain as a function of the light intensity present sharp threshold behavior. A similar behavior is shown by the saturating refractive index change. In agreement with experiments, predicted thresholds appear shifted towards higher intensities (up to a 104 factor) when the Nb-Li concentration is decreased or the temperature is increased. The model also explains very recent data on the threshold enhancement with the Fe2+/Fe3+ ratio in optical waveguides. (c) 2008 Optical Society of America.