掺Yb3+闪烁晶体的研究进展

掺Yb³⁺闪烁晶体是新近发展起来的一类闪烁体,有可能用于探测太阳中微子.本文简要介绍了掺Yb³⁺闪烁晶体的电荷迁移发光的机理以及基质晶体对温度猝灭与浓度猝灭的影响.综述了具有石榴石结构和钙钛矿结构的两类掺Yb³⁺闪烁晶体的研究进展,特别是Yb:YAG和Yb:YAP晶体的生长、闪烁性能以及应用前景.最后,对掺Yb³⁺闪烁晶体的未来研究方向做了展望.     

Yb3+、Ho3+掺杂浓度及晶粒尺寸对NaYF4∶Yb3+,Ho3+上转换材料发光的影响

EDTA作为络合剂,在pH值为5的条件下,采用水热法制备了NaYF4∶Yb3+,Ho3+微米棱柱上转换材料,研究了掺杂浓度和晶粒尺寸对上转换发光特性的影响。实验发现材料发光主要以绿光为主,最佳的Yb3+、Ho3+掺杂浓度分别为25%和1%,高于此值均会出现浓度猝灭效应。通过改变溶液中NaF/NH4HF2摩尔比来调控晶粒的尺寸,发现随着晶体颗粒尺寸的增大,材料中Yb3+浓度增加,从而使上转换发光增强。     

YAG晶体中Yb~(3+)对Er~(3+)的敏化作用

根据能级跃迁速率方程得出Yb,Er:YAG中各能级布居数与Er3+离子浓度的关系.并与单掺Er:YAG中各能级布居数相比较,讨论共掺Yb3+对Er3+的波长为1.64和2.94μm两荧光的影响.结合作者关于红外光激励Yb,Er:YAG能量上转换为可见光工作,提出将Yb,Er:YAG晶体研制成以半导体激光器为激励源的可见光和1.64μm红外光的双波长全固化激光器的设想.     

Yb^3＋掺杂双包层光子晶体光纤制备研究

本文报道了国内自行研制和制备的以高功率光子晶体光纤激光器为目标的Yb3+掺杂双包层光子晶体光纤.给出了Yb3+掺杂多组分玻璃芯棒和以此为芯的双包层光子晶体光纤的制备流程,工艺和关键技术.对制备的Yb3+掺杂多组分玻璃、双包层光子晶体光纤进行-系列的物理属性、热学和光谱测试,并通过计算分析得到相对优秀的掺杂多组分玻璃配方(Yb3+-(2 mol%)-SiO2(70 mol%)-MgO-CaO-BaO-Li2O-Al2O3(2 mol%)).样品中的Yb3+掺杂双包层光子晶体光纤具有结构规则传光性能良好等优点,为自行开发高功率光子晶体光纤激光器提供材料器件基础.     

液闪测量3H活度TDCR与ESCR法的比较

基于TDCR与ESCR两种不同的液体闪烁测量方法,使用两台液体闪烁计数器分别测量3H系列猝灭源,探测效率均随着猝灭程度的增加而降低,TDCR方法具有较高的探测效率,且测量值的偏差总体较小;采用ESCR方法测量猝灭指数较大的3H样品时,宜提前基于所用闪烁液的体积对3H的优值因子进行调试,并使用多组低测量效率的猝灭标准源来拟合猝灭曲线。     

硼酸铋玻璃中Er3+和Yb3+的光谱特性

采用熔体冷却法制备了单掺Er3+和Yb3+的硼酸铋玻璃,并利用理论方法计算了硼酸铋玻璃中Er3+和Yb3+的光谱参数.详细分析了硼酸铋玻璃中Er3+和Yb3+离子光谱参数与玻璃组成和掺杂浓度的关系,并研究了Yb3+离子的辐射陷阱效应.实验表明,掺Er3+和Yb3+的硼酸铋玻璃是一种具有潜在发展前途的固体激光器和光纤放大器用激光材料.     

颜色可调Y(PO3)3:Tb3+,Yb3+上转换发光材料的共沉淀制备及性能

采用共沉淀法制备Tb3+,Yb3+共掺杂Y(PO3)3上转换发光材料,通过X射线粉末衍射仪(XRD)、扫描电镜(SEM)、傅里叶红外光谱(FT-IR)和上转换荧光光谱仪(UPL)对制备产物的结构和性能进行表征分析.结果表明,所制备样品属于单斜晶系空间群为P21/c的Tb3+和Yb3+共掺杂Y(PO3)3晶体.在近红外光的激发下,所制备Y(PO3)3:x Tb3+,20％(摩尔分数,下同)Yb3+样品发射出Tb3+特征的蓝绿色光.Tb3+掺杂量直接影响着制备产物的上转换发光性能,当Tb3+掺杂量为2％ ～10％时,Tb3+的5 D4→7 F6发射峰分裂为481 nm和491 nm两个发射峰;当掺杂量为5％～20％时,位于547 nm处绿光发射为最强发射峰;当Tb3+掺杂量高于20％时观察到浓度猝灭现象.Tb3+/Yb3+的掺杂量比例和近红外光激发功率密度对所制备样品的上转换发光性能也有明显影响.适当调节样品中Tb3+/Yb3+掺杂比例可实现对制备的Y(PO3)3:x Tb3+,20％Yb3+样品的上转换发射蓝绿光颜色的调控.对Y(PO3)3:Tb3+,Yb3+样品的上转换发光机理进行探索,其中属于Tb3+特征的5 D3→7 FJ(J=6,5,4)和5 D4→7 FJ(J=6,5,4,3)跃迁带发射分别属于三光子吸收和双光子吸收机制.     

CaF2:20Yb2Er/Na@CaF2:Ce纳米材料近红外二区发光性能研究

利用热分解法制备了CaF₂:20Yb2Er/Na@CaF₂:Ce纳米颗粒，并对其NIR-Ⅱ发光性能和荧光寿命进行了探讨。研究结果表明，在980 nm光源激发下，其NIR-Ⅱ发光性能强度约为CaF₂:20Yb2Er的68倍，且位于1 525 nm处的荧光寿命为2.29 ms。该体系Yb³⁺作为敏化剂，Er³⁺作为激活剂，Na⁺共掺杂使晶体场的局部对称性改变，核壳结构的构建使发光中心的荧光猝灭最小化，壳层结构引入Ce³⁺可以使得Er³⁺与Ce³⁺在界面处产生交叉弛豫。由此可见，将离子共掺杂和构建核壳结构两种策略结合起来更有利于NIR-Ⅱ发光性能的提升。综上，CaF₂:20Yb2Er/Na@CaF₂:Ce纳米颗粒在生物成像领域具有潜在的应用价值。     

激光非线性复合功能晶体的研究和发展

简要回顾了激光非线性复合功能晶体(即自倍频晶体)的发展过程,从结构、生长和性能等方面对现已研制发展的Nd:Mg:LiNbO₃(NMLN)、Nd_xY_1-xAl₃(BO₃)₄(NYAB)、Cr:KTP、LaBGe_^O5:Nd³⁺、β’-Gd₂(MoO₄)₃:Nd³⁺(GMO:Nd³⁺)、掺Nd³⁺或Yb³⁺的ReCa₄O(BO₃)₃(ReCOB;Re=Gd、Y)(即 Nd:GdCOB、Yb:GdCOB、Nd:YCOB、Yb:YCOB)、Yb:BaCaBO₃F 等几种主要类型的自倍频晶体的研究现状进行了总结,并对该类晶体的发展做了展望.     

PEG修饰YF_3微米晶的溶剂热合成及Y_(1.2)F_3:Yb_(0.18)~(3+)/Er_(0.01)~(3+)上转换荧光性质

采用溶剂热方法,乙醇和乙二醇的混合溶剂中,150℃条件下,反应12h,成功制备了YF3:Yb3+/Er3+晶体,和PEG-6000修饰的YF3:Yb3+/Er3+晶体。通过X射线粉末衍射,扫描电镜(SEM),红外光谱(IR)和荧光分光光度计对样品的组成、结构和荧光性质进行了表征和分析。结论为:YF3:Yb3+/Er3+晶体与YF3标准卡PDF#74-0911相符,而PEG-6000修饰的YF3:Yb3+/Er3+晶体的标准卡为PDF#32-1431,说明PEG的修饰导致晶体结构的变化。室温下,以980nm为激发光源,YF3:Yb3+/Er3+晶体和PEG修饰的YF3:Yb3+/Er3+晶体的荧光发射峰位置均为551nm、666nm和832nm,其分别对应于Er3+离子的4S3/2→4I15/2,4F9/2→4I15/2和4S3/2→4I13/2跃迁。但荧光强度不同。讨论了表面活性剂聚乙二醇的加入对YF3:Yb3+/Er3+晶体形貌,尺寸及荧光性质的影响,并对Yb3+/Er3+上转换发光机理进行了讨论。     

CsCdF3:Cr3+晶格畸变及其Cd2+-空位研究

按照零场分裂（ＺＦＳ）的三阶微扰理论和叠加晶场模型,建立了ＺＦＳ参量Ｄ与ＣｓＣｄＦ３：Ｃｒ＾３＋晶格结构之间的定量关系,同时考虑了晶格畸变和Ｃｄ＾２＋空位对零场分裂参量Ｄ的贡献,计算了ＣｓＣｄＦ３：Ｃｒ＾３＋晶体的零场分裂参量Ｄ,计算结果与实验符合甚好,证明了晶格畸变和Ｃｄ＾２＋空位的存在,同时得到ｒ＾３＋离子的Ｆ＾－离子向中心Ｃｒ＾３＋离子分别移动Ｘ１＝０．００２９１ｎｍ,Ｘ２＝０．００１ｎｍ,     

Effect of Yb concentration on optical properties of Yb:CaF2 transparent ceramics

In Yb:CaF₂, the coordination of Yb³⁺ in the CaF₂ lattice determines the spectroscopic properties that make Yb:CaF₂ a good candidate for high power laser applications. In this work, we measure the optical absorption, emission, and fluorescence lifetime of 0.1, 1, 5, and 10 at% Yb:CaF₂ ceramics to determine whether Yb³⁺ substitutes as hexamer clusters giving rise to the tenability and long fluorescent lifetime observed in Yb:CaF₂ single crystals. Absorption and emission spectra show that the concentration of Yb³⁺ present in hexamer clusters, as opposed to isolated ions, increases with increasing Yb³⁺ content. Fluorescence lifetime also increases with increasing Yb³⁺ content. Laser testing on a 1 at% Yb:CaF₂ transparent ceramic demonstrates that these materials are viable laser gain media.     

Monophase domain, fibers single crystals grown by the micro-pulling down technique and optical characterisation of LiGd1−xYbx(WO4)2

We have determined the single phase domain of LiGd_1−xYb_x(WO₄)₂. The lattices parameters decrease as a function of Yb³⁺ substitution in Gd³⁺ sites. Transparent LiGd_1−xYb_x(WO₄)₂ fibers single crystals were successfully grown by the micro-pulling down technique (μ-PD). The Yb³⁺-doped LiGd(WO₄)₂ fibers single crystals have been pulled under stationary stable growth conditions corresponding to flat crystallization interface with meniscus length equal to 120 μm. The fibers diameters varied from 0.5 to 1 mm depending on the capillary die diameter, pulling rate and the molten zone temperature. Fibers single crystals free of defects are observed for Ytterbium concentration in the melt up to 5 at%. Above this limit, inclusions and cracks appear and the optical quality of the fibers were deteriorated. The emission spectra of Yb³⁺-doped LiGd(WO₄)₂ were investigated.     

Crystal growth and spectroscopic studies of novel Yb-doped K5Nd(MoO4)4 single crystals

K₅Nd(MoO₄)₄ crystals with different Yb³⁺ concentrations were grown using Czochralski technique. Room-temperature absorption spectra were recorded and assigned on the basis of Dieke's diagram for Nd³⁺ ion; the standard Judd-Ofelt theory has been used to analyze the spectra. Increase of Yb³⁺ concentration leads to variation of the corresponding Judd-Ofelt intensity parameters. Significant contribution of the Yb↔Nd energy transfer into the formation of the Nd³⁺ absorption spectra causes the observed changes. After illumination of the crystals with CW Nd:YAG laser changes of the birefringence for the laser line of CW He-Ne laser at 633 nm were studied. Birefringence changes show good correlation with the content of Yb ions.     

Significant reduction of upconversion emission in CaTiO3: Yb, Er inverse opals

Inverse opal photonic crystals of Yb³⁺, Er³⁺ co-doped CaTiO₃ (CaTiO₃: Yb, Er) were prepared using self-assembled polystyrene templates combined with the infiltration of sol-gel precursor. The influence of the photonic band gap on upconversion emission of Er³⁺ has been investigated in the CaTiO₃: Yb, Er inverse opals. Significant reduction of the upconversion emission was detected if the photonic band-gap overlaps with the Er³⁺ ions emission band.     

Characterization of Yb:YAG and Yb:YAP scintillators by means of LAAPD at temperature around 100 K

A new class of scintillators based on charge-transfer luminescence of the Yb³⁺ ion is being investigated for the last few years. The main prospect for these scintillators is in neutrino physics. The crystals manifest maximum light output at temperatures 100 K<T<150 K. In this range Large Area Avalanche Photodiodes (LAAPD) are the best photodetectors. In this work Yb(25%):YAG and Yb(5%):YAP scintillators were characterized by means of a 16 mm diameter API LAAPD at temperatures around 100 K. Light yield and energy resolution were determined. Light yield non-proportionality was detected for all the crystals comparing light output at 661.6 and 59.6 keV peaks.     

Lu2O3:Yb3+, Ho3+纳米粉体的发光性能研究

采用共沉淀工艺合成了Yb3 离子和Ho3 离子共掺杂的Lu2O3纳米粉体,研究了粉体的斯托克斯(Stokes)和反斯托克斯(Anti-Stokes)发光特性以及煅烧温度对粉体发光性能的影响.在氙灯447.5nm和半导体激光器980nm激发下样品均发射出明亮的绿光,观察到了不同Ho3 离子浓度掺杂的纳米粉体的浓度淬灭现象.发射强度与激发功率的关系表明Anti-Stokes发光是双光子过程,能量转移是主要的上转换机制.Ho3 离子的5F4,5S2能级在不同波长激发下的衰减时间也证实了浓度淬灭及能量转移现象.     

Growth and optical properties of (Yb3−xYx)Al5O12:Ce single crystals

To improve the infrared emission of Yb³⁺ ions doped in the garnet host Y₃Al₅O₁₂ (YAG) single crystal through the energy transfer from Ce³⁺ to Yb³⁺ ions, the 〈1 1 1〉-oriented YAG:Ce³⁺, YAG:Yb³⁺, YAG:(Ce³⁺, Yb³⁺) and Yb₃Al₅O₁₂:Ce³⁺ (YbAG:Ce³⁺) single crystals were grown using the Czochralski Method, respectively. The excitation and emission spectra of these garnet single crystals were characterized. In YAG:Ce³⁺ crystal, the yellow emission of Ce³⁺ ions present, but it was completely extinguished in YAG:(Ce³⁺, Yb³⁺) crystal and YbAG:Ce³⁺ crystal. However, the characteristic absorption bands of Ce³⁺ still existed in the excitation spectrum of Yb³⁺ ions, which showed that the energy absorbed by Ce³⁺ ions can be transferred to Yb³⁺ ions for its infrared emission.     

Growth of Yb-doped Y2O3 single crystal rods by the micro-pulling-down method

The rare-earth sesquioxides (RE₂O₃, RE = Lu, Y and Sc) are very promising host crystals for advanced laser diode (LD)-pumped Yb³⁺-doped solid-state lasers due to unusual combination, almost unique of favourable structural, thermal and spectroscopic properties which are described. In spite of these favourable properties, the bulk single crystal growth technology for the rare-earth sesquioxides has not been established yet. The extremely high melting temperature at around 2400 °C has prevented it. However, we shall show that yttrium oxide crystals (Yb_xY_1−x)₂O₃, x = 0.0, 0.005, 0.05, 0.08 and 0.15 of cylindrical shape as laser rods with 4.2 mm in diameter and 15-20 mm in length have been grown from rhenium crucibles by the micro-pulling-down method. The crystal quality characterisation of undoped Y₂O₃ crystal was determined using X-ray rocking curve (XRC) analysis. Yb were homogeneously distributed in Y₂O₃ host crystal.