一种新型掺铒碲酸盐玻璃的光谱性质研究

研究了一种新型掺Er³⁺碲酸盐玻璃的光谱性质；应用Judd-Ofelt理论计算了碲 酸盐玻璃中Er³⁺离子的强度参数Ω(Ω₂=479×10^-20 cm²,Ω₄= 152×10^-20cm²,Ω₆=066×10^-20cm2)，计算了离子的自发跃迁概 率，荧光分支比；应用McCumber理论计算了Er³⁺的受激发射截面(σ_{e=1040×1 0^-21cm²)，Er³⁺离子⁴I13/ 2→⁴I15/2发射谱的 荧光半高宽(FWHM=655nm)及各能级的荧光寿命(⁴I13/2 能级为τrad =399ms)；比较了不同基质玻璃以及不同类型碲酸盐玻璃中Er³⁺离子的光谱 特性， 结果表明该掺铒碲酸盐玻璃具有更好的光谱性能，更适合于掺Er³⁺光纤放大 器实现宽带和高增益放大. 关键词： 碲酸盐玻璃 光谱性质 Judd-Ofelt理论}     

掺Er3+碲酸盐玻璃的光谱性质与Judd-Ofelt理论分析

用高温熔融法制备了碲酸盐玻璃(70TeO₂-9B₂O₃-6Nb₂O₅-5Na₂O-10ZnO-1%(质量分数)Er₂O₃)样品。测试了玻璃样品的吸收光谱和荧光光谱。应用Judd-Ofelt理论计算了Er³⁺离子的谱线强度、自发辐射跃迁几率、荧光分支比、辐射寿命等光谱参数,并拟合了相应的强度参数Ω_t(t=2,4,6)(Ω₂=8.01×10^-20cm²,Ω₄=2.09×10^-20cm²,Ω₆=1.15×10^-20cm²)。结果发现该碲酸盐玻璃具有较大的Ω₂值,说明Er—O键的共价性强于它在硅酸盐、锗酸盐、氟化物、铋酸盐和磷酸盐玻璃中的共价性。Er³⁺在碲酸盐玻璃中⁴I_13/2→⁴I_15/2跃迁几率约为492s^-1,表明Er³⁺可能有较强的1.5μm发射。分析了Er³⁺在碲酸盐玻璃中能级⁴I_13/2→⁴I_15/2发射的荧光半峰全宽(FWHM=73nm),并应用McCumber理论计算了Er³⁺的受激发射截面(σ_e=1.08×10^-20cm²),发现其FWHM×σ_e远大于Er³⁺在铋酸盐、磷酸盐、锗酸盐和硅酸盐玻璃中的受激发射截面,说明碲酸盐玻璃是一种制备宽带光纤放大器的优良基质材料。     

Er3+/Yb3+共掺碲硼硅酸盐玻璃的光谱性质和热稳定性研究

制备了系列Er³⁺/Yb³⁺共掺碲硼硅酸盐玻璃样品(85-x)TeO₂-15B₂O₃-xSiO₂ (TBS x=0,5,10,15,20 mol%).测试和分析了样品的吸收光谱、荧光光谱、能级寿命、红外透射光谱及差热特性.并通过对Er³⁺离子⁴I_13/2→⁴I_15/2跃迁发射谱线的高斯拟合，设计了一个简单的四能级结构估算了Er³⁺离子⁴I_13/2和⁴I_15/2能级在碲硼硅酸盐中的Stark分裂情况.研究表明SiO₂的引入能有效地改善玻璃的热稳定性和光谱性能，玻璃析晶温度T_x与玻璃转变温度T_g之差(ΔT=T_x-T_g)可达178℃，说明碲硼硅酸盐是一种适合于光纤拉制的玻璃基质材料.比较了不同基质玻璃中Er³⁺离子的荧光半高宽和受激发射截面，结果表明TBS玻璃系统具有较好的带宽性能，是一种优良的宽带光纤放大器候选基质材料. 关键词： 碲硼硅酸盐 热稳定性 高斯拟合 -基')" href="#">OH^-基     

Ce3+对Er3+/Yb3+共掺TeO2-WO3-ZnO玻璃发光性能的影响

在Er³⁺/Yb³⁺共掺TeO₂-WO₃-ZnO玻璃中引入Ce³⁺，研究了Ce³⁺对Er³⁺1.5μm发射性能及其上转换发光性能的影响。结果表明，随Ce³⁺浓度的增加Er³⁺1.5μm波段的荧光强度先增强后降低，优化的Ce³⁺掺杂浓度在2.07×10²⁰/cm³左右；1.5μm波段的荧光寿命则随Ce³⁺浓度的增加有轻微降低，从3.4ms降到3.0ms，但Ce³⁺浓度的增加对1.5μm波段的荧光半高宽基本无影响；Er³⁺/Ce³⁺间的交叉弛豫Er³⁺(⁴I_11/2)+Ce³⁺(²F_5/2)→Er³⁺(⁴I_13/2)+Ce³⁺(²F_7/2)使玻璃的上转换发光强度大大降低，但在过高的Ce³⁺浓度下，Er³⁺/Ce³⁺间的另一交叉弛豫Er³⁺(⁴I_13/2)+Ce³⁺(²F_5/2)→Er³⁺(⁴I_15/2)+Ce³⁺(²F_7/2)则使Er³⁺⁴I_13/2能级粒子数减少，导致1.5μm波段荧光强度和荧光寿命降低. 关键词： 碲钨酸盐玻璃 发光性能 3+离子')" href="#">Er³⁺离子 3+离子')" href="#">Ce³⁺离子 交叉弛豫     

980nm脉冲激发下Er3+掺杂材料中4I13/2→4I15/2跃迁的瞬态行为(英文)

在过去的几十年人们对Er³⁺掺杂的玻璃材料进行了广泛的研究,因为Er³⁺的⁴I_13/2→⁴I_15/2跃迁能够给出适合红外光通讯窗口的1.5μm的发射。据我们所知,目前关于脉冲激光激发下Er³⁺掺杂材料1.5μm发射的动力学行为研究报道仍很少。我们引入了转移函数理论,研究了980nm脉冲激发下Er³⁺的⁴I_13/2能级荧光的动力学行为。发现在980nm脉冲激发后,其荧光衰减遵循双指数规律,⁴I_13/2能级布居分为指数上升和指数下降两个过程。     

Er3+离子浓度对ZnS:ErF3薄膜交流电致发光特性的影响

本文研究了Er³⁺离子浓度对ZnS:ErF₃薄膜交流电致发光(ACEL)特性的影响。I(⁴F_9/2→⁴I_15/2)受Er³⁺离子浓度的影响较大,随Er³⁺离子浓度增高,I(⁴F_9/2→⁴I_15/2)增强,甚至超过I(²H关键词：     

Er,Yb:YAG微晶玻璃发光特性的研究

高温熔制Er³⁺，Yb³⁺离子掺杂CaO-Y₂O₃-Al₂O₃-SiO₂系统玻璃，并进行微晶化处理，研究了微晶玻璃中Er³⁺离子的发光及上转换发光特性，分析了微晶玻璃上转换发光机理.结果表明：原始玻璃经热处理得到了Er,Yb:YAG微晶玻璃，微晶玻璃中Er³⁺离子在室温下⁴I_13/2→⁴I_15/2跃迁产生横盖1450—1650nm区间的超宽带荧光，荧光半高宽达180nm，这可能由于YAG微晶相中Er³⁺离子与玻璃相中残留Er³⁺离子的共同发光；Er³⁺与Yb³⁺离子局域基质声子能量的降低使微晶玻璃Er³⁺离子上转换发光强度与原始玻璃相比显著提高，绿光、红光上转换荧光强度比玻璃样品分别增强约7和3倍；微晶化后Er³⁺，Yb³⁺离子局域环境发生变化也导致微晶玻璃中Er³⁺离子绿光、红光上转换发光相对强度发生变化. 关键词： 铒 镱:钇铝石榴石 微晶玻璃 荧光光谱     

用于GaAs太阳能电池的NaYF4中Tb3+-Er3+耦合对的光谱转换

观测到一种以Tb³⁺-Er³⁺进行光谱转换的量子剪裁现象。一个高能紫外光子(Tb³⁺的⁷F₆→⁵L₁)被量子剪裁成两个低能光子:一个是近红外光子(Er³⁺的⁴I_9/2→⁴I_15/2),另一个是蓝色光子(Tb³⁺的⁵D₄→⁷F₆),它们两个 都可以被GaAs太阳能电池有效地吸收。量子剪裁效率高达188%,接近理论极限的200%。从Tb³⁺(⁵L₁→ ⁵D₄) 到Er³⁺(⁴I_15/2→⁴I_9/2)的能量传递的能量失配是237 cm^-1,比NaYF₄中的声子能400 cm^-1小,能量传递是近共振的。Tb³⁺施主间的能量迁移可以近似地用扩散模型处理, 从Tb³⁺-Er³⁺对之间能量传递的初始过程发现,偶极-偶极相互作用占主导地位。     

Er3+/Yb3+共掺碲钨酸盐玻璃的热稳定性和1.5μm波段的光谱性质

制备了Er³⁺/Yb³⁺共掺的碲钨酸盐玻璃样品,TeO₂-WO₃-R_mO_n(R_mO_n=PbO,BaO,La₂O₃,Bi₂O₃),研究了样品的热稳定性和1.5μm波段的光谱性质。碲酸盐中引入WO₃的目的是为提高基质的声子能量,使Er³⁺离子⁴I_13/2→⁴I_15/2的多声子弛豫速率增加,从而提高⁴I_13/2能级上的Er³⁺离子数,这对提高1.5μm处的荧光强度有利,另外加入WO₃也能提高碲酸盐玻璃的抗析晶能力。测试了样品的FT-IR光谱,发现碲钨酸盐玻璃样品中存在着TeO₄、TeO₃、WO₄和WO₆结构体。周围环境的不对称性导致Er³⁺在1.5μm处的光谱有非均匀的展宽和大的受激发射截面。Er³⁺在70TeO₂-20WO₃-10Bi₂O₃玻璃中⁴I_13/2→⁴I_15/2能级发射的荧光半峰全宽(FWHM)为77nm,应用McCumber理论计算的受激发射截面(σ^peak)为1.03×10^-20cm²。其FWHM×σ_peak乘积远大于掺Er³⁺的铋酸盐、磷酸盐、碲酸盐和硅酸盐玻璃,说明碲钨酸盐玻璃是一种制备宽带光纤放大器优良基质材料。     

近紫外激发具有颜色可调的Er3+/Eu3+共掺BiOCl荧光粉

本文采用固相法在500℃合成了Er³⁺/Eu³⁺共掺BiOCl 荧光粉, 并通过XRD, SEM, 吸收, 激发和发射光谱研究了其结构、形貌和发光特性. XRD 和SEM结果表明在500℃下即可成功合成纯四方相片层结构的Er³⁺/Eu³⁺共掺BiOCl荧光粉. 吸收光谱表明掺杂Er³⁺/Eu³⁺离子使BiOCl形成杂质能级; 激发光谱显示该荧光粉具有来自于基质BiOCl价带(VB)到导带(CB)跃迁的优异宽带近紫外激发特性. 在380 nm近紫外光激发下, 同时获得了Er³⁺离子和Eu³⁺离子的特征发射峰, 其中发光中心位于410 nm (²H_9/2→⁴I_15/2), 525 nm (²H_11/2→⁴I_15/2), 554 nm (⁴S_3/2→⁴I_15/2), 673 nm (⁴F_9/2→⁴I_15/2)的发射峰来自于Er³⁺离子的跃迁, 而581 nm(⁵D₀→⁷F₀), 594 nm (⁵D₀→⁷F₁), 622 nm (⁵D₀→⁷F₂), 653 nm (⁵D₀→⁷F₃), 699 nm (⁵D₀→⁷F₄)的发射峰则来自于Eu³⁺离子的跃迁. 值得注意的是, 与传统Er³⁺/Eu³⁺掺杂的材料不同, 该荧光粉还具有独特高效的紫光(Er³⁺)和长波红光(Eu³⁺)发射特性, 分析表明这与BiOCl的结构有关; 并且通过改变掺杂浓度, 实现了发光颜色由黄绿光→黄光→橙红光的调节. 研究结果表明Er³⁺/Eu³⁺共掺BiOCl荧光粉有望成为一种潜在的近紫外激发白光LED荧光粉.     

Low temperature specific heats of erbium dihydrine. Magnetic transition and crystal field splitting effects

The specific heat of erbium dihydride, ErH_1.99, was measured in the temperature range from 1.8–230 K. A λ-type specific heat anomaly, most probably due to an antiferrómagnetic transition has been found at T_N = 2.13 ± 0.03 K. The influence of the crystal field of cubic symmetry on the splitting of the ground state ⁴I_{$\text{15}\text{2}$} of the Er³⁺ ion was analysed and the conclusion was drawn, that the doublet Γ₇ is the lowest lying crystal-field level.     

Electron paramagnetic resonance in Y1−cH1.92:Erc

We have investigated the EPR of isotopically enriched ¹⁶⁸Er³⁺ in Y_1?cH_1.92:Er_c where c = 100 and 1400 ppm, at both 1.4 and 9 GHz and between 1.5 and 50 K. Resonance lines were observed from Er³⁺ ions in both sites of cubic symmetry and sites of axial symmetry. We determine the numbers of Er³⁺ in cubic, and C_4v axial symmetry to be in the ratio 2:1. The cubic site resonance line is at g = 6.85 ± 0.07 and is attributed to a Γ₇ doublet. The linewidth has a linear thermal broadening of 3.9 ± 0.05 gauss K^-1 below circa 7 K. From the nonlinear thermal broadening above this temperature we determine the first excited state, in the cubic crystal field scheme, to be a Γ₈ at 35 ± 10 K above the Γ₇ ground state. We have investigated the origins of the (T = 0) residual linewidth for the ions in cubic symmetry, and conclude there to be a small but significant contribution due to unresolved transferred hyperfine structure from the surrounding hydrogen nuclei.     

Enhanced upconverted photoluminescence in Er and Yb codoped ZnO nanocrystals with and without Li ions

The upconversion luminescence spectral intensity of Er³⁺ in Er³⁺ and Yb³⁺ codoped ZnO nanocrystals with and without Li⁺ are investigated. Yb³⁺ ions as a tradition sensibilizer have efficient energy transfer processes from Yb³⁺ (²F_5/2) to Er³⁺ (⁴I_13/2, ⁴I_11/2, ⁴F_9/2), which lead to the increment of upconversion luminescence intensity. Following by adding Li⁺ to the Er³⁺ and Yb³⁺ codoped ZnO nanocrystals, the upconversion intensity emitted by Er³⁺ ions is found greatly enhanced. The enhancement is attributed to the distortion of the local field symmetry of Er³⁺ ions, so increases various intra-4f transitions of Er³⁺ ions. Both Yb³⁺ and Li⁺ can disperse Er³⁺ ions in specimen, so reduced the interaction between neighboring Er³⁺ ions.     

Zero-field splitting of <Superscript>4</Superscript><Emphasis Type="Italic">T</Emphasis><Subscript>2</Subscript> term for 3d<Superscript>3</Superscript> ions in tetragonal symmetry

By taking into account slight interactions, i.e. spin-spin, spin-other-orbit and orbit-orbit interactions, in addition to spin-orbit interaction, the zero-field splitting of ⁴ T ₂ state for 3d³ ions at tetragonal symmetry has been studied. The convergence of the approximation perturbation formula of ⁴ T ₂ state for 3d³ ions at tetragonal symmetry has been investigated, and the contributions to zero-field splitting arising from magnetic interaction and tetragonal crystal field are discussed. It is found that there exists combined mechanism between magnetic interactions and tetragonal crystal field.      

Spectra of optical absorption and energy levels diagram of Er<Superscript>3+</Superscript> ions in bulk crystals of aluminum nitride

The absorption spectra of the Er³⁺ ions embedded in the AlN matrix have been investigated. The admixture of erbium was introduced in bulk AlN crystals by diffusion. The absorption lines, which are associated with the intraconfigurational electronic f–f-transitions from the ground ⁴ I _15/2-state to the levels of ion Er³⁺ excited states have been observed in the spectral range of 370–700 nm. The transitions to the state levels ⁴ F _9/2, ² H _11/2, ⁴ F _7/2, ⁴ F _5/2, ² H _9/2, and ⁴ G _11/2 have been investigated in detail at the temperature T = 2 K. The number of the observed lines for these transitions coincides with the theoretically possible one for the electronic f–f-transitions in the ions Er³⁺, which are in the crystal field with the symmetry below cubic. The narrowness of the observed lines and their number convincingly testify the replacement of preferably one regular crystalline position by erbium ions. The implementation of Er³⁺ in the Al³⁺ position with the local symmetry C _3v appears the most probable. The energy positions of the levels of excited states for the investigated transitions have been determined. The diagram of the Er³⁺ ion energy levels in the AlN crystals has been built.     

Crystal field efects on the electron spin resonance of rare-earths in YPd3: Comparison with inelastic neutrons scattering experiments

We report low temperature Electron Spin Resonance experiments on diluted Er, Dy and Yb in YPd₃. The host cubic crystal field leaves a Γ₆ ground state for Er³⁺, and a Γ₇ excited state could be observed at 18 ± 4K for this system. A lower lying Γ₇ was measured for Yb³⁺ in YPd₃, and a broad undefined resonance for Dy³⁺ in this host. A comparison of our data with those obtained by Inelastic Neutrons Scattering is given.     

The effect of Er3+-ion concentration on the Er3+ : 4I13/2 → 4I15/2 transition in tellurite glasses

The effect of Er³⁺ concentration on the Er³⁺?:?⁴I_13/2?→?⁴I_15/2 emission in tellurite glasses has been investigated. The full width at half-maximum increased with the increasing concentration of Er₂O₃ in tellurite glasses. The effect of local structure of Er³⁺ ions and related spectroscopic changes are taken into account to explain the line broadening. Inhomogeneous broadening due to the distribution of crystal field around the Er³⁺ ion has little effect on the absorption spectra. Highly efficient energy trapping between the ions was identified from the time-resolved analysis of the fluorescence decay and is found to be responsible for the extended lifetime at intermediate concentrations of Er³⁺ ions in tellurite glasses. The effect of temperature on spectral line shape has been determined for analysing the contribution of Boltzmann population on line broadening. The increased population of the overlying Stark sublevels at the ⁴I_13/2 energy level via direct pumping and/or interaction between Er³⁺ ions were also found to be significant for enhancement in spectral line shape at higher concentrations of Er³⁺ ions in tellurite glasses. It was observed that at higher concentrations of Er³⁺ ions in glass also enhance the local symmetry of ions, which is apparent from the absorption band of the Er³⁺?:?⁴I_15/2?→?²H_11/2 hypersensitive transition.     

Electron paramagnetic resonance of Er<Superscript>3+</Superscript> ions in a polycrystalline α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

The EPR spectra of rare-earth Er³⁺ ions in a polycrystalline corundum α-Al₂O₃ synthesized by the sol-gel technology were revealed. It is shown that the EPR spectra belong to the Er³⁺ ions in the ground state corresponding to the lower Stark sublevel of the ⁴ I _15/2 term and can be described by the spin Hamiltonian of axial symmetry with an effective spin S = 1/2 and the g tensor with components g _‖ = 12.176 and g _⊥ = 4.14. The average value of the g tensor (〈g〉 = 6.82) corresponds to the Γ₇ state in a cubic field. Erbium is assumed to substitute for aluminum in the Al₂O₃ corundum crystal. The local symmetry C ₃ of the Al³⁺ ion remains despite the pronounced expansion of the lattice around the Er³⁺ ion.     

High index of refraction via quantum interference in a three-level system of Er^3＋-doped yttrium aluminium garnet crystal

A simple three-level system is proposed to produce high index of refraction with zero absorption in an Er^3＋-doped yttrium aluminium garnet （YAG） crystal, which is achieved for a probe field between the excited state 4I13/2 and ground state 4I15/2 by adjusting a strong coherent driving field between the upper excited state 4I11/2 and 4I15/2. It is found that the changes of the frequency of the coherent driving field and the concentration of Er^3＋ ions in the YAG crystal can maximize the index of refraction accompanied by vanishing absorption. This result could be useful for the dispersion compensation in fibre communication, laser particle acceleration, high precision magnetometry and so on.     

Indirect measurements of the Jahn-Teller quenched spin-orbit splitting in the 5T2g-state of KMgF3:Fe2+

The energy separation of the first excited spin-orbit States Γ_3g, Γ_4g from the Γ_5g ground state, in the orbital ⁵T_2g triplet state of Fe²⁺ in KMgF₃, has been estimated from temperature dependence measurements on the 7860 cm^-1 zero-phonon-line (ZPL) transition from Γ_5g to the orbital ⁵E_g doublet state. Using a simplified crystal field energy level model, we find the Γ_5g Γ_3g, Γ_4g separation to be ～30 cm^-1, indicating that the vibronic Jahn-Teller coupling is considerably stronger in KMgF₃:Fe²⁺ than in MgO:Fe²⁺. Far infrared absorption data on KMgF₃:Fe²⁺ in magnetic fields up to 6T, are found to be consistent with this interpretation.