LiNbO_3及LiTaO_3晶体的光折变性能研究

光折变效应是电光晶体的一种效应，ＬｉＮｂＯ３及ＬｉＴａＯ３晶体的光折变效应对于该材料的应用具有重要意义，本文从理论和实验两方面研究ＬｉＮｂＯ３及ＬｉＴａＯ３晶体的光析变效应特性，理论分析与实验结果吻合得很好。     

重掺镁LiNbO3:Fe晶体的光谱与光折变特性研究

研究了重掺镁ＬｉＮｂＯ３：Ｆｅ晶体的透射光谱与光折变特性。结果表明,ＬｉＮｂＯ３：Ｆｅ晶体在重掺镁后,镁离子把晶体中的铁离子“挤”入铌位是重掺镁ＬｉＮｂＯ３：Ｆｅ晶体抗光折变的原因所在。在重掺镁（≥５ｍｏｌ％）ＬｉＮｂＯ３：Ｆｅ的 ,作为施主中心的Ｆｅ＾２＋的特征吸收“台阶”的消失和３５０４ｃｍ＾－１的ＯＨ吸收带的出现,都直接证明了铁离子从锂位进入了铌位,并以Ｆｅ＾３＋Ｎｂ的形式存在。     

掺锌铌酸锂（LiNbO3：Zn）晶体的物性测量

本文配制了系列掺锌铌酸锂多晶料，测量了掺锌铌酸锂的熔化温度及居里温度随掺锌量的变化。用熔融提拉法生长了不同掺锌量的铌酸锂单晶。研究了锌在晶体中的分凝、晶体的抗光折变能力和倍频转换效率。实验结果表明：（１）在铌酸锂晶体中，随掺锌量的增加，ＬｉＮｂＯ３：Ｚｎ的熔化温度呈下降趋势，而居里温度线性上升。（２）在掺锌铌酸锂晶体中，调节锌的掺杂量，可以找到分凝系数近于１的掺锌浓度。（３）当掺锌量大于７ｍｏ１％时，ＬｉＮｂＯ３：Ｚｎ晶体与ＬｉＮｂＯ３：Ｍｇ具有同样的抗光折变能力，前者的倍频转换效率比后者稍大。     

LiNbO_3：Fe~（3＋1）晶体中Fe~（3＋）离子的发射光谱研究

在１００００～４００００ｃｍ－１范围内，观测得ＬｉＮｂＯ３晶体掺Ｆｅ３＋离子的发射光谱与赵等的理论预言基本一致，从而证明了Ｆｅ３＋离子杂质在ＬｉＮｂＯ３中取代Ｎｂ５＋离子。     

LiNbO3：Fe^3＋晶体中Fe^3＋离子的发射光谱研究

在１００００￣４００００ｃｍ＾－１范围内，观测得ＬｉＮｂＯ３晶体掺Ｆｅ＾３＋离子的发射光谱与赵等的理论预言基本一致，从而证明了Ｆｅ＾３＋离子杂质在ＬｉＮｂＯ３中取代Ｎｂ＾５＋离子。     

LiNbO_3的抗光折变与它的OH~－谱研究

测试了不同掺杂，不同组分ＬｉＮｂＯ＿３样品的红外吸收谱．提出在一致熔化组分ＬｉＮｂＯ＿３晶体中，Ｎｂ可变价和Ｌｉ的空位模型。解释了ＯＨˉ谱的３峰结构。在掺镁阈值以上，用镁占铌位和铁占铌位的缺陷模型，解释了ＯＨˉ谱紫移及３５０４ｃｍ￣（－１）峰出现的原由，进而对镁占铌位和铁占铌位进行了肯定。     

声学超晶格中的横场激发超声波产生

从理论与实验两方面研究了横场激发技术对声学超晶格ＬｉＮｂＯ３（ＬＮ）晶体谐振特性的影响，两者之间得到了很好的吻合，采用提拉法，制得了沿Ｚ轴生长的具有周期性铁电畴结构的ＬＮ单晶，将此晶体先Ｚ切，再Ｘ切成样品，经过适当的处理后，在Ｘ面镀上电极，采用ＨＰ８５１０Ｃ网络分析仪测得的样品的横场激发谐振频率为５０２ＭＨｚ，与理论计算的谐振频率５００ＭＨｚ基本一致，这种“横场激发”利用了ＬＮ的最大机电耦合系数，     

强烈机械搅拌对Al－Cu10％合金结晶方式的影响

分析了强烈机械搅拌作用对Ａｌ－Ｃｕ１０％合金结晶组织的影响。指出强烈机械搅拌作用下形成的粗大玫瑰状组织和无分枝的颗粒状晶体是由于强烈机械搅拌作用导致液固界面前方形成很薄的溶质原子富集层，使得晶体平面生长，并在生长过程中分枝以粘合方式粗化的结果。     

河口水中Cd（Ⅱ）在Fe2O3.nH2O（am.）上的特性吸附及界面…

本文叙述了盐度为５‰的河口水中Ｃｄ（Ⅱ）在Ｆｅ２Ｏ３．ｎＨ２Ｏ（ａｍ２）上的吸附等温线以及ｐＨ盐度对吸附百分率的影响，着重讨论了吸附对固－液界面电性的影响和不同盐度（ｓ＝２．５‰，５．０‰，７．５‰）时吸附Ｃｄ（Ⅱ）后变化的等电点，结果表明：Ｃｄ（Ⅱ）在Ｆｅ２Ｏ３．ｎＨ２Ｏ（ａｍ）上的吸附为特性吸附，固液界面的电性变化及等电点移动与体系的ｐＨ和Ｃｄ（Ⅱ）的吸附量有关，盐度上升，吸附量降低，由吸附～     

掺稀土元素 Er~(3+) 的 LiNbO_3 波导激光器设计

掺稀土元素Ｅｒ３＋的ＬｉＮｂＯ３波导激光器设计卢文杰陈淑芬（北京理工大学光电工程系１０００８１）掺稀土元素Ｅｒ３＋的ＬｉＮｂＯ３通道型连续输出的波导激光器作为一种新型激光器，在光集成方面具有独特优势而显示出良好的发展前景。由于铌酸锂晶体材料的优点以及...     

Structure and properties of Li-rich Zn-doped LiNbO3 Crystal

The Li-rich Zn-doped LiNbO3 (LN) crystals were grown by the Czochralski method. The structure of the crystals was measured by ultraviolet-visible absorption spectra. The results indicated that the Li-rich Zn-doped LN crystals had the same characteristics as the pure LN crystal. After Zn2+ entered into the lattice of Li-rich Zn-doped LN crystal, it replaced NbLi firstly. When there was no NbLi, Zn2+ replaced Li+ then. The second harmonic generation (SHG) property of Li-rich Zn-doped LiNbO3 crystal was measured. The results showed that the SHG conversation efficiency of Li-rich Zn-doped LiNbO3 crystals was higher than that of Zn-doped LiNbO3 crystals.     

多晶硅凝固界面形态演化过程的相场法模拟分析

采用有限差分法求解小平面晶生长Wheeler相场模型,对多晶硅凝固界面形态演化过程进行相场模拟,详细分析了初始晶核条件、扰动强度和时间步长对界面形态演化的影响。结果表明:在多晶硅凝固过程中,九个晶核初始条件下,固液界面比较平坦,晶核生长空间差异小,易于形成垂直于生长界面的棱角胞晶组织。随着扰动强度的增加,棱角胞晶出现侧向分支,根部缩颈严重甚至出现熔断现象。选择强度为0.01的界面扰动,能够真实再现多晶硅凝固界面形态演化过程。在保证计算结果稳定性条件下,增加时间步长能够提高相场模拟计算效率。     

防止重掺砷CZ单晶硅组分过冷的探讨

在探讨组分过冷数学模型的基础上,针对重掺砷CZ单晶硅的生长,理论计算了防止组分过冷时固液界面处晶体温度梯度G_S的临界值为51.32~33.10 K/cm.以此为依据,设计了具有较大温度梯度的18寸(60 cm)晶体生长热场,以数值模拟的方法,给出了固液界面处晶体的温度梯度G_S的模拟值为54.68~38.14 K/cm.在晶体等径生长的各个阶段,固液界面处晶体的温度梯度G_S的模拟值均在防止组分过冷的临界值之上,可以有效避免晶体生长过程中组分过冷的发生,并利用实际晶体生长试验的结果验证了以上分析的有效性.     

Optical Property of LiNbO3 Crystal Codoped with In, Mg and Fe

In2O3, MgO and Fe2O3 were doped in LiNbO3 and Czochralski method was used to grow In:Mg:Fe:LiNbO3 crystals. The OH- extension transmission spectra, light scattering resistance ability, two wave coupled diffraction efficiency and response time of the crystal were measured. Codoping In and Mg in crystal will improve its light scattering resistance ability and response time. Doping In can increase the ability to replace antisite Nb and decrease the doping quantity of Mg. All these are propitious to improve the optical homogeneity of crystal. Doping Fe can improve the photorefractive sensitivity for LiNbO3 crystal. We discussed the site of In, Mg and Fe in LiNbO3 crystals and the influence of the absorption peak of OH- transmission spectra on photorefractive property for LiNbO3 crystal.     

Optical Property of LiNbO3 Crystal Codoped with In, Mg and Fe

In2O3, MgO and Fe2O3 were doped in LiNbO3 and Czochralski method was used to grow In:Mg:Fe:LiNbO3 crystals. The OH- extension transmission spectra, light scattering resistance ability, two wave coupled diffraction efficiency and response time of the crystal were measured. Codoping In and Mg in crystal will improve its light scattering resistance ability and response time. Doping In can increase the ability to replace antisite Nb and decrease the doping quantity of Mg. All these are propitious to improve the optical homogeneity of crystal. Doping Fe can improve the photorefractive sensitivity for LiNbO3 crystal. We discussed the site of In, Mg and Fe in LiNbO3 crystals and the influence of the absorption peak of OH- transmission spectra on photorefractive property for LiNbO3 crystal.     

LiTaO_3单晶的层向生长机制

对 LiTaO_3单晶的生长机制进行了理论分析。根据提拉法生长条件下的温度分布,预料该晶体的主要生长机制是层向生长,并得到了实验证实。讨论了晶体生长的过程和机制后指出,凡是提拉法生长条件下表面出现生长棱的晶体,均具有层向生长机制。     

大直径掺钕铌酸锂晶体生长及其光学性能研究

在LiNbO3多晶料中依次掺入0.2mol%,0.5mol%和1.0mol%的钕,采用我们自主开发的计算机控制直拉法生长大直径Nd:LiNbO3晶体,测试了晶体的紫外-可见吸收光谱、荧光光谱和红外吸收光谱。由紫外-可见吸收光谱确定泵浦光波长,由荧光光谱确定激光振荡波长;采用X射线荧光光谱分析法测量了Nd:LiNbO3晶体中钕的有效分凝系数,结果是Nd:LiNbO3晶体中钕的有效分凝系数随着钕掺杂浓度的增加而减小。     

The Effect of Oxidation／Reduction Disposing on Optical Properties of Mg： Fe： Mn： LiNbO3 Crystals

The congruent tri-doped Mg: Mn: Fe: LiNbO3 crystal has been grown by Czochralski method. Some crystal samples are reduced in Li2CO3 powder at 500℃ for 24 hours or oxidized for 10 hours at 1100 ℃ in Nb2O5 powder. Compared with As-grown Mg:Mn:Fe:LiNbO3, the absorption edge in UV-Vis. absorption spectrum of the oxidized sample and the reduced shifts to the violet and the red, respectively. Reduction increases the absorption of crystals in visible light region. In two-wave coupling experiments, the writing time, maximum diffraction efficiency and the erasure time of crystal samples in the same conditions are determined. The results indicate that oxidation and reduction disposing has great effect on the holographic recording properties of these crystals. The reduced crystal exhibits the fastest response time of 160 s anmng the crystal series. The mechanism of post-disposing effect on the holographic recording properties of Mg:Mn:Fe:LiNbO3 crystals are investigated.     

Electrochromic effect in domain-inversion process in LiNbO3： Ru： Fe crystals

A reversible electrochromic effect accompanying domain-inversion during the electrical poling process in LiNbO3： Ru： Fe crystals at room temperature has been observed. In electrode area, both electrochromism and domain-inversion occur alternately, and electrochromism is also reversible during back-switch poling, which is experimentally verified and whose mechanism is briefly explained using a microstrncture ferroelectric model. In addition, because of the enhancing elcctrochromic effect, different from the undoped LiNbO3 crystals, the coercive filed （21.0 kV/mm or so） measured in LiNbO3： Ru： Fe is lower than its breakdown field, thus providing a possible new technique for realizing the domain-inversion by constant electric field rather than a pulsed one.     

Studies of Photorefractive Crystals of Double-Doped Ce,Fe:LiNbO3

In this paper, photorefractive crystals of Ce, Fe:LiNbO3 are systematically studied. The crystals have been grown by Czochralski method. The samples with different doping concentrations and oxidation/reduction treatments have been fabricated. Their photorefractive properties were experimentally investigated by using two-beam coupling. The results show that the photorefractive efficiency depends on the dopant concentration, oxidation/reduction treatment, and light wavelength. The doping mechanism is also discussed here.