We observed the photorefractive spatial dark-soliton stripes in LiNbO3:Fe crystal, and demonstrate the planar waveguide property of refractive index profile induced by these spatial dark-soliton stripes. We suggest a new toothed to form the planar waveguide utilizing the grating fixing technique.

Based on a multi-three-wave mixing model, we theoretically study the resistance against light-induced scattering in LiNbO3: M sM-Mg21, Zn21, In31, Sc31d crystals. We have simulated the intensity angular distribution of light-induced scatterings. We have also shown that the total light-induced scattering will be much less than 1% of the incident light intensity when the photovoltaic field Eph is less than 4.03 106 Vym. Phase gratings and signal beams can still be formed and amplified effectively in LiNbO3: Mcrystals, with Eph less than 4.03 106 Vym.

Based on a multiwave mixing model, we explain the symmetrical and broad light-induced scattering effect in LiNbO3: Fe crystal sheets. Analytical results are given in the undepleted-pumps approximation. The competition between forward small-angle scattering and climbing lights and its relation to the ratio of the size of the incident-light spot to the crystal thickness are discussed. The intensity angle distribution of the forward small-angle light-induced scattering is studied theoretically and experimentally. We suggest that the selfdefocusing effect of the LiNbO3: Fe crystal plays an important role in the formation of the fanning intensity angle distribution.

On the basis of the idea that signal gratings have a faster formation rate than noise gratings and signal gratings have a slower erasure rate than noise gratings under the same erasing beam, we report a new technique to suppress or eliminate the noise in image processing in photorefractive crystals. A general theoretical analysis and experimental results in LiNbO3:Fe crystals are given.

We analyze the valence and electronic shell configuration characters of all damage-resistant dopants found in LiNbO3 crystals up to now. We show that all damage-resistant dopants have only one valence state. We also show that the electronic shell configurations of these damage-resistant ions are filled fully, as are the cases of the inert elements. From this point of view, we conclude that the anti-site NhLi should be involved in the charge transport process, while the Li vacancy VLI is not involved in the charge transport process. It also can give us some insights about how to select a damage-resistant dopant for LiNbO3 crystal.