Study Of Growth And Optical Holographic Storage Properties Of Scandium Series Doped Lithium Niobate Crystal

The Sc:Fe:LiNbO₃ and Mg:Sc:Fe:LiNbO₃ crystals are grown by the Czochraski method,and the crystals have no macroscopic defect and exhibit good optical homogeneity,The appropriate technological conditions are chosen during the crystal growth process to avoid the crystal crack and decrease the component asymmetry due to the solute segregation.X-ray powders diffraction of the crystals were performed.The results showed that there is no new phase appeared in the doped LiNbO₃ crystals.The crystals hold the same lattice structure as the pure congruent lithium niobate crystal,but the lattice constants have comparable change.The doped ions can only replace Li⁺,Nb_Li⁴⁺ or Nb⁵⁺.The dependence of the change of the absorption band in the IR spectra and the absorption edge in the UV-Vis spectra on the change of Sc₂O₃,MgO and Li/Nb ratio in the raw materials are investigated.The threshold concentration and location of Sc in doped LiNbO₃ crystals are confirmed.When the Sc doping concentration is below the threshold concentration,Sc³⁺ ions replace the antisite Nb(Nb_Li⁴⁺,the Nb⁵⁺ located at the Li site) firstly and Fe ions locate normal Li⁺ sites.When the Sc doping concentration is up to the threshold concentration,all of Nb_Li⁴⁺ ions are replaced by Sc³⁺ ions,and Sc³⁺ ions will occupy normal Li⁺ and Nb⁵⁺ sites.The threshold concentration of Sc is about 3mol%in congruent Sc:Fe:LiNbO₃ crystals.The threshold value decreases with the Li/Nb ratio increasing.In the near stoichiometric Sc:Fe:LiNbO₃ crystal,the threshold concentration is only 0.3mol%.The threshold concentration in the Sc:Fe:LiNbO₃ crystal was higher than that of Mg:Sc:Fe:LiNbO₃ crystal.In Mg:Sc:Fe:LiNbO₃ crystal,the Sc concentration reaches the threshold priority.When the MgO concentration increases further,and the doping concentration of Sc₂O₃ and MgO concentration exceeds the threshold concentration,the "Sc-Mg threshold concentration" is achieved.The photorefractive and photorefractive resistance properties are measured by two wave coupling and transmission facula distortion method,respectively. With the increasing of Sc doping concentration,Mg doping concentration or Li/Nb ratio,the diffraction efficiency and dynamic range of crystals decrease,the response time and the erasure time decrease,and the photorefractive sensitivity increase.The optical damage resistance of the co-doped Sc:Fe:LiNbO₃ crystals have obviously changed when the Sc doping concentration reached the threshold value. It is two orders of magnitude higher than that of Fe:LiNbO₃ crystals.With the Li/Nb increases,the optical damage resistances of crystals also improve.In the stoichiometric Sc:Fe:LiNbO₃ crystals,With the Sc doping concentration increase further,the optical damage resistances of Sc:Fe:LiNbO₃ crystals gradually decrease above the the threshold until the MgO doped.The holographic storage experiment was carried out by using the Fe:LiNbO₃ crystal and Sc:Fe:LiNbO₃ crystals as storage medium,the quality of the output picture stored in the Sc(5mol%):Fe:LiNbO₃ crystal was higher than that of Fe:LiNbO₃ crystal and near stoichiometric Sc(0.1mol%):Fe:LiNbO₃ crystal.The results indicated that the photorefractive effect can be affected by doping the Sc ions to the crystals and changing the Li/Nb ratio.It is helpful for improving the application in holographic storage.