【作者】 代丽；

【导师】 王义杰；

【作者基本信息】 哈尔滨理工大学 ， 材料物理与化学， 2007， 硕士

【摘要】 本文采用提拉法,首次生长了Mg含量变化的Mg:Ce:Fe:LiNbO₃晶体,根据晶体生长理论,改善掺杂LiNbO₃晶体的生长工艺参数（温度梯度、晶体生长速度、晶体旋转速度）,保持了平坦的固-液界面,研制出无宏观缺陷、光学均匀性好的晶体。并对晶体进行了X-射线衍射分析、红外吸收光谱、紫外-可见吸收光谱和二波耦合实验。晶体的X-射线衍射表明,Mg:Ce:Fe:LiNbO₃晶体的晶格缺陷在掺镁量没有达到阈值浓度时,随掺镁量的增大而逐渐增大,当掺镁量达到阈值浓度时又有下降。晶体的红外吸收光谱表明,Ce⁴⁺和Fe³⁺进入晶格,分别占据Nb位和Li位,形成Ce_Nb^2-和Fe_Li⁽2+_缺陷,晶体通过增加Nb_Li⁴⁺和Li空位进行电荷补偿;Mg²⁺进入晶格,首先取代NbL 4i+ ,当达到阈值浓度时,Mg离子开始进入Nb位和Li位,形成Mg_Nb³⁺和3 Mg_Li⁺ ,形成自身的电荷平衡。晶体的紫外-可见吸收光谱表明,当掺镁量没有达到阈值浓度时,Mg:Ce:Fe:LiNbO₃晶体的吸收边随掺镁量的增大发生紫移,当掺镁量达到阈值浓度后,晶体的吸收边又发生相对红移。结合Mg:Ce:Fe:LiNbO₃晶体的X-射线衍射分析、红外吸收光谱、紫外-可见吸收光谱结果,分析了掺杂离子在晶体中的占位情况。Mg:Ce:Fe:LiNbO₃晶体并没有因为Mg、Ce和Fe杂质的掺入而出现新相,仍为三方晶系。并且确定了杂质Mg、Ce、Fe在掺杂LiNbO₃晶体中的占位情况以及Mg在掺杂LiNbO₃晶体阈值浓度。利用二波耦合测试了晶体的光折变性能,系统研究了镁铈铁铌酸锂晶体的弱光非线性光学效应。结果表明:随着掺镁量的增加,衍射效率下降,写入时间缩短,光折变灵敏度增加,动态范围降低;利用透射光斑畸变法研究了镁铈铁铌酸锂晶体镁掺杂量对晶体抗光损伤性能的影响,结果表明:随着镁掺杂量的增加,晶体的抗光损伤阈值升高,其中Mg（6mol%）:Ce:Fe:LiNbO₃晶体的抗光损伤阈值比Ce:Fe:LiNbO₃高出2个数量级以上。更多还原

【Abstract】 Mg:Ce:Fe:LiNbO₃ crystals are grown at the first time by Czochralski method with different concentration of Mg. According to the theory of crystals growth, growth parameters（temperature gradient, pulling speed and rotating speed） are modified. The crystals grown with appropriate parameters have no macroscopic defect and exhibit good optical homogeneity. Crystals’properties are studied by XRD analysis、infrared absorption spectra、UV-Visible absorption spectra and wave coupling experiments.XRD results show that the lattice defects increase with the increase of Mg contents when the concentration of Mg is lower than threshold and decreases when concentration of Mg reaches the threshold.The infrared absorption spectra shows that Ce⁴⁺ and Fe³⁺ occupy the Nb sites and Li sites, respectively, fallowed by the appearance of Ce_Nb^2- and Fe_Li²⁺ defects. Crystals compensate charges by increasing Nb_Li⁴⁺ and Li vacancies. Mg ions entering LiNbO₃ crystal firstly substitute Nb_Li⁴⁺ and then occupy Nb sites and Li sites when the Mg²⁺ concentration is up to the threshold, forming Mg_Nb^3- and 3 Mg_Li⁺ and self-charges-balance.The UV-Visible absorption spectra of Mg:Ce:Fe:LiNbO₃ crystals shows that the absorption edge of Mg:Ce:Fe:LiNbO₃ shifts towards violet band with the increase of Mg contents and shifts towards red band relatively when the Mg contents reach threshold concentration.Ion sites in the LiNbO₃ crystals are analyzed according to the XRD analysis、infrared absorption spectra and the UV-Visible absorption spectra. No new phases appears when the LiNbO₃ crystals are doped with Mg、Ce and Fe. All these crystals are still LiNbO₃ with trigonal system. The locations of Ce, Fe, Mg ions and the threshold concentration of Mg in doped LiNbO₃ crystals are confirmed.The photorefractive properties are measured by two wave coupling. The weak light nonlinear optical effects of Ce, Fe-series LiNbO₃ crystals are studied. The results show that the diffraction efficiency and dynamic range decreases, the sensitivity increases and the writing time is shortened with the increasing of the Mg doped concentration. The dependence of Mg contents on the low photorefractive resistant properties is studied by facula distortion method. The results show that the photo- damage resistance threshold increases with the increasing of Mg concentration. When Mg doping concentration is about 6mol%, the photodamage resistance threshold improves greatly to 2 orders of magnitude higher than than that of Ce:Fe:LiNbO₃.更多还原