【作者】 钱艳楠；

【导师】 王锐；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2012， 博士

【摘要】 掺铒光波导放大器（EDWA）是未来微光子系统的重要组件之一，Er:LiNbO₃晶体作为EDWA的基体材料具有稳定性高和集成性能好等优点，并可以将Er³⁺离子的激光性能和LiNbO₃晶体的非线性光学性能结合在一起。Er:LiNbO₃晶体发射的1.54μm波段近红外发光对应现代光纤通信的标准“窗口”波长。然而，Er:LiNbO₃晶体的光损伤效应限制了晶体的实际应用。本论文选择不同价态Zn²⁺，In³⁺和Zr⁴⁺离子提高晶体的光损伤性能，研究了不同价态抗光损伤离子对Er:LiNbO₃晶体缺陷结构和光学性能的影响，为获得高效率1.54μm波段近红外发光提供了理论依据和实验指导。采用第一性原理的方法，研究了Zn²⁺，In³⁺和Zr⁴⁺离子掺杂LiNbO₃晶体的几何结构。结果表明，Zn²⁺，In³⁺和Zr⁴⁺离子在晶体中均优先占据Li位。研究了Zn²⁺，In³⁺和Zr⁴⁺离子在Li位上的稳定性，认为在Er:LiNbO₃晶体中，Zn²⁺离子会促使Er³⁺离子进入Nb位，形成Er³⁺离子团位束。In³⁺离子对Er³⁺离子占位影响不大。Zr⁴⁺离子在Li位上稳定性较低，易于进入Nb位，使Er³⁺离子继续占据Li位。采用Czochralski方法生长了Er:LiNbO₃晶体，通过研究不同浓度Er³⁺离子掺杂同成分LiNbO₃晶体的缺陷结构和不同激发波长下的近红外发射光谱，上转换发射光谱和上转换布局机制，提出了Er³⁺离子占位与光学性能的关系，即Er:LiNbO₃晶体中Er³⁺离子团位束的形成增大了交叉弛豫的发生概率，在980nm激发光源下，Er³⁺离子团位束会抑制1.54μm波段近红外发光。研究了不同[Li]/[Nb]比（分别为0.94，1和1.25）对Er:LiNbO₃晶体缺陷结构和光学性能的影响。结果显示，当[Li]/[Nb]=1时，Er:LiNbO₃晶体中的Er³⁺离子团位束被解离，发射高效率的1.54μm波段近红外发光。研究了Er³⁺（3mol%）/Zn²⁺（3,6和7mol%）:LiNbO₃晶体的缺陷结构和光学性能，结果显示，Er³⁺离子并未影响Zn²⁺离子在晶体中的阈值浓度；当Zn²⁺离子掺杂浓度低于其阈值浓度时，晶体中的Er³⁺离子团位束被解离，引起了1.54μm波段近红外发光的增强；当Zn²⁺离子掺杂浓度高于其阈值浓度时，晶体中会再次形成Er³⁺离子团位束，导致1.54μm波段近红外发光降低。结合第一性原理计算结果和Er³⁺离子占位和光学性能的关系，生长了Zn²⁺/Er³⁺摩尔比例为3/1.5（mol%/mol%），6/1（mol%/mol%）和7/1.5（mol%/mol%）的Zn/Er:LiNbO₃晶体。光学测试结果表明Zn/E（r6mol%/1mol%）:LiNbO₃晶体具有最强的1.54μm波段近红外发光。Zn/Er:LiNbO₃晶体的OH-吸收峰Lorentz三峰分解和上转换绿光寿命测试结果表明，Zn²⁺离子促使Er³⁺离子在低于其阈值浓度时从Li位进入Nb位，在晶体中形成了Er³⁺离子团位束。研究了In/Yb/Er:LiNbO₃晶体(In³⁺离子掺杂浓度为1，2和3mol%)的缺陷结构和光学性能。研究发现，Yb3+和Er³⁺离子共掺降低了In³⁺离子的阈值浓度；当In³⁺离子达到阈值浓度时，晶体中形成Er³⁺离子团位束。由于Yb3+离子的敏化作用，In/Yb/Er:LiNbO₃晶体中Er³⁺离子团位束的形成有利于1.54μm波段近红外发光。In³⁺离子掺杂浓度为阈值浓度时，晶体1.54μm波段发射最强。Zr/Er:LiNbO₃和Zr/Yb/Er:LiNbO₃晶体近红外发射光谱测试结果显示Zr⁴⁺离子提高了1.54μm波段近红外发射效率。通过晶体Raman光谱和Er³⁺离子4I11/2→4I15/2跃迁在1020nm处的衰减曲线测试结果分析了Zr⁴⁺离子增强近红外发光强度的机理是晶体最大声子能量的增大。不同价态Zn²⁺，In³⁺和Zr⁴⁺离子掺杂Yb/Er:LiNbO₃晶体的1.54μm波段发射性能结果显示，Zn²⁺离子降低了1.54μm波段发射，In³⁺离子对此波段发光没有影响，Zr⁴⁺离子大幅度增强了1.54μm波段发射。因此Zr/Yb/Er: LiNbO₃晶体将成为最有前景的优良波导器件基质材料。采用Judd-Ofelt理论研究了Zn²⁺， In³⁺和Zr⁴⁺离子掺杂Er:LiNbO₃和Yb/E r:LiN bO₃晶体的光谱性质，Zr/Yb/Er:LiNbO₃晶体具有最大的光学品质因子值。通过McCumber和Füchtbauer-Ladenburg理论分析了抗光损伤离子掺杂Er:LiNbO₃和Yb/Er:Li NbO₃晶体1.54μm波段的发射性能，结果显示，晶体均具有大的发射截面积，适合作为EDWA的基体材料。更多还原

【Abstract】 Er-doped wavelength amplifiers （EDWAs） will be one of the key componentsof futher microphotonic systems, and Er:LiNbO₃crystals, used as the host materialsfor EDWAs, have excellent advantages such as the high stabilization and integration.Furthermore, Er:LiNbO₃crystals could combine the laser performances of Er³⁺ionwith the nonlinear characteristics presented by LiNbO₃crystal. Er:LiNbO₃emits1.54μm near infrared emission, which corresponds to the standard communication“window” wavelength. Howerve, the practical applications of Er:LiNbO₃crystalsare limited by the optical damage effect. Different valence Zn²⁺, In³⁺and Zr⁴⁺ionsare chosen to enhance the optical damage of LiNbO₃crystals. We performinvestigations on the effect of different valence optical damage resistant ions on thedefect structure and optical characteristics of Er:LiNbO₃crystals, which provide thetheoretical and experimental direction for us to obtain the high efficient1.54μmnear infrared emission.The geometry structure of LiNbO₃crystals doped with Zn²⁺, In³⁺and Zr⁴⁺ionsare calculated by the first principle theory, which shows that Zn²⁺, In³⁺and Zr⁴⁺ionsoccupy Li sites firstly. The stuies on the stability of Zn²⁺, In³⁺and Zr⁴⁺ionsoccupied Li sites show that Zn²⁺ions will push Er³⁺ions into Nb sites, and the Er³⁺clusters sites are formed in Er:LiNbO₃crystals, and In³⁺ions have little effect on theoccupancy of Er³⁺ions, and the low stability of Zr⁴⁺ion makes Er³⁺ions stilloccupy Li sites.The Er:LiNbO₃crystals are grown by Czochraski method. The defect structureof Er:LiNbO₃with different Er³⁺ion concentration, as well as the near infraredemission, upconversion emission and mechanism under different excitationwavelength are studied. It has been proposed that the formation of Er³⁺cluster sitescould increase the rate of cross relaxation processes. Under980nm excitation, Er³⁺cluster sites will suppress the1.54μm near infrared emission. Studies on the effectof [Li]/[Nb] ratio （is equal to0.94,1and1.25, respectively） on the defect structureand optical characteristics of Er:LiNbO₃crystals show that as for [Li]/[Nb]=1, theEr³⁺cluster sites are dissociated and the strongest1.54μm emission is observed inEr:LiNbO₃crystal.The studies on the defect structure and optical characteristics of Er³⁺（3mol%）:LiNbO₃crystals doped with3,6and7mol%Zn²⁺ions show that thethreshold concentration of Zn²⁺ion is not affected by Er³⁺ions in Zn/Er:LiNbO₃crystal. When the concentration of Zn²⁺ions is lower than its threshold, the Er³⁺cluster sites are dissociated by Zn²⁺ions, which results in the enhancement of1.54 μm near infrared emission. When the concentration of Zn²⁺ions is higher than itsthreshold, the reformantion of Er³⁺cluster sites are observed, which decreases the1.54μm near infrared emission. Combined the first principle theory with the relationbetween the occupancy and optical characteristics of Er³⁺ions, the Zn/Er:LiNbO₃crystals with the3/1.5,6/1and7/1.5mol ratio of Zn²⁺/Er³⁺are grown. The strongest1.54μm emission is found in Zn/Er （6mol%/1mol%）:LiNbO₃crystal. Stuies on theOH-absorption Lorentz three decomposition and the decay curves of upconversiongreen emission show that Zn²⁺ions would push Er³⁺ions from Li sites into Nb sites,and the Er³⁺cluster sites are formed at lower concentration.The defect structure and optical characteristics of Yb/Er:LiNbO₃crystal dopedwith1,2and3mol%In³⁺ions are studied. The experiemtal results show that Yb3+and Er³⁺ions decrease the threshold concentration of In³⁺ions. When theconcentration of In³⁺ion is equal to its threshold, the Er³⁺cluster sites are formed.The formation of Er³⁺cluster sites is favor for the1.54μm near infrared emissiondue to the sensization effect of Yb3+ion. The strongest intensity of1.54μmemission is observed in Yb/Er:LiNbO₃crystal codoped with the thresholdconcentration of In³⁺ions.Zr⁴⁺ion doping enhances the1.54μm emission in Zr/Er:LiNbO₃andZr/Yb/Er:LiNbO₃crystals. Raman spectra and the decay curves of Er³⁺4I11/2→4I15/2transition at1020nm indicate that the enhancement of the1.54μm emission arisesfrom the increased maximum phonon energy of host material. The near infraredspectra of Yb/Er:LiNbO₃crystals doped with the different valence Zn²⁺, In³⁺andZr⁴⁺ions suggest that Zn²⁺doping decreases the1.54μm emission, In³⁺ions havealmost no effect, and Zr⁴⁺ions lead to a drastical increase of1.54μm emission.Zr/Yb/Er:LiNbO₃crystal could be considered as the most outstanding host materialsfor waveguides.The spectral characteristics of Er:LiNbO₃and Yb/Er:LiNbO₃crystals dopedwith Zn²⁺, In³⁺and Zr⁴⁺ions are studied by Judd-Ofelt theory, and Zr/Yb/Er:LiNbO₃crystal has the largest spectroscopic quality factor. The emission performance of1.54μm emission is analyzed by McCumber and Füchtbauer-Ladenburg theory. Allthe crystals have large emission cross section, which is suitable for the hostmaterials of EDWA.更多还原