Cooperative energy transfer and frequency upconversion in Yb3+-Tb 3+ and Nd 3+-Yb 3+-Tb 3+ codoped GdAl3(BO3)4 phosphors

Polycrystalline GdAl₃(BO₃)₄ phosphors codoped with Yb³⁺/Tb³⁺ and/or Nd³⁺/Yb³⁺/Tb³⁺ have been synthesized by combustion method. Upon excitation with a 980 nm laser diode, an intense green upconversion luminescence has been observed in GdAl₃(BO₃)₄:Yb,Tb phosphor. The quadratic dependence of the luminescence on the pump-laser power indicating a cooperative energy transfer process. Meanwhile, it is noticed that upon excitation with 808 nm laser diode, intense luminescence has clearly been detected in GdAl₃(BO₃)₄:Nd,Yb,Tb phosphor. The luminescence intensity exhibits also a quadratic dependence on incident pump-laser power. However, no green-emission has been observed in GdAl₃(BO₃)₄ phosphors codoped with Yb³⁺/Tb³⁺ or Nd³⁺/Tb³⁺ respectively upon excited at 808 nm laser diode. A proposed upconversion mechanism involving energy transfer from Nd³⁺ to Yb³⁺, and then a cooperative energy transfer process from two excited Yb³⁺ to Tb³⁺ has been presented.     

Optical spectroscopy of Cr3+ and Cr3+-Tm3+ in alkaline silicate glasses

Conclusions Alkaline silicate glasses seem to be good candidates as host materials for codoping with Cr³⁺ and Tm³⁺. Cr³⁺ ions occupy mainly low-field sites in them, and their broadband emission overlaps Tm³⁺ excitation. As a consequence very high efficiency for the energy transfer Cr³⁺→Tm³⁺ is achieved with moderate concentrations of these ions. Moreover, the average lifetime of the Cr³⁺ ions in codoped glasses is long enough to allow significant energy storage by flashlamp pumping. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 5, pp. 115–120, September–October, 1995.     

Stark splitting and energy transfer between Dy3+-Ho3+ and between Tb3+-Er3+ in calcium-lithium borate glass

Fluorescence spectrum of Dy³⁺, Dy³⁺-Ho³⁺, Tb³⁺ and Tb³⁺-Er³⁺ doped in calibo glass have been studied using Ar⁺ and excimer lasers. Non-radiative energy transfer from trivalent dysprosium and terbium (donors) to holmium and erbium (acceptors) respectively has been observed on the basis of decrease in the life time of the levels and reduction in fluorescence intensity of Dy³⁺ and Tb³⁺ on increasing Ho and Er concentrations. The interaction mechanism of donor and acceptor ions is found to be dipole-dipole in both cases. Various parameters such as donor-acceptor distances, non-radiative energy transfer efficiency (η) and energy transfer probability (P _da) have been computed. Stark splitting have also been marked in several intense transition of the two.     

Er~(3+)及Er~(3+)/Yb~(3+)掺杂纳米晶CaWO_4的发光性质

利用共沉淀法制备了Er3+掺杂及Er3+/Yb3+共掺杂纳米晶CaWO4发光粉体,室温下观察到Er3+的下转换和上转换特征发射。研究了不同煅烧温度、不同掺杂浓度对Er3+离子特征发射的影响。结果表明:随着煅烧温度的升高,发射强度增强;掺杂浓度的改变,导致了Er3+的浓度猝灭现象,其适宜的掺杂原子数分数为0.6%。同时观测到O-W的电荷迁移态与稀土离子之间的能量传递现象,并给出了能量传递的模型。对Er3+的上转换研究观察到:在976nm激光激发下Yb3+对Er3+的上转换发射起到了很好的敏化作用,两个Yb3+同时将能量以共振方式传递给一个Er3+离子,Er3+、Yb3+共掺杂样品的绿光上转换过程展示了双光子过程。     

Luminescence properties of Nd3+, Sm3+ and Eu3+ intercalated CdPS3

Nd³⁺, Sm³⁺ and Eu³⁺ have been intercalated by cation exchange into CdPS₃. The photoluminescence and IR spectra show the creation of cadmium cation vacancies. Crystal field analysis indicates that the rare earths have entered the intralamellar vacancies and formed a complex defect center with C₂ or lower symmetry.     

Spectroscopy of Ce3+-doped and Ce3+-concentrated scintillators

Institute of Physics, Czech Academy of Sciences, Cukrovarnicka 10, 16200 Prague 6, Czech Republic. Published in Zhurnal Prikladnoi Spektroskopii, Vo. 62, No. 5, pp. 71–77, September–October, 1995.     

Preparation and fluorescence properties of Yb3+ and Er3+ co-doped GdAlO3 phosphors

Yb³⁺ and Er³⁺ co-doped GdAlO₃ phosphors are prepared by the sol–gel method. The effect of doping concentration on the structure and fluorescence properties is investigated by X-ray diffraction (XRD) and photoluminescence, respectively. XRD pattern indicates that the sample structure belongs to orthorhombic. The photoluminescence results show that both green and red fluorescence emission and upconversion emission intensities decrease with an increase in Yb³⁺ concentration due to the cross-relaxation process between Yb³⁺ and Er³⁺ ions. Based on the emission spectra, the mechanism of the upconversion emission is discussed, and we concluded that the upconversion emission is a two-photon process.     

在NaGdF4：Tm3+, Dy3+中Gd3+间的能量迁移及Gd3+-Dy3+能量传递量子效率

基于量子剪裁基本原理,通过光谱技术研究NaGdF₄:Tm³⁺,Dy³⁺在一个真空紫外光子激发下获得两个蓝色光子的可能性。在这种化合物中,量子剪裁通过下转换,即通过应用不同镧系离子间的能量传递进行。通过对Tm 4f¹²-4f¹¹5d激发,部分能量从Tm³⁺离子5d态直接传递给Gd³⁺,然后在Gd³⁺-Tm³⁺之间发生交叉弛豫,剩余能量从Gd³⁺传递给Dy³⁺,产生两个可见光子发射,一个来自Tm³⁺的¹G₄-³H₆跃迁,另一个来自Dy³⁺的⁴F_9/2-⁶H_15/2跃迁。主要研究获得以NaGdF₄:Tm³⁺,Dy³⁺为基础的新型具有更高效率,更高稳定性和更强真空紫外(VUV)吸收量子剪裁发光粉的可能性。各种光谱技术,如光致发光、激发和衰减等被用来表征不同Dy³⁺浓度掺杂NaGdF₄中Gd³⁺晶格间能量迁移引起的施主Gd³⁺和受主Dy³⁺之间的能量传递。结果表明Gd³⁺离子之间存在能量迁移,随之交换相互作用引起施主与受主(Gd³⁺-Dy³⁺)之间的能量传递。通过Bursh-tein等人关于激发态的弛豫理论,施主-受主能量传递参数k_DS可以从Gd³⁺的⁶P_7/2发射的衰减计算出。Gd³⁺-Dy³⁺能量传递量子效率也可以得到。NaGdF₄:Tm³⁺和NaGdF₄:Tm³⁺,Dy³⁺是由水热法制备的,NaGdF₄:Dy³⁺是由文献[4]方法制备的。发射光谱和激发光谱通过自制的VUV光谱仪和F-4500测量。衰减曲线由OPO激光器激发获得Gd³⁺-Dy³⁺之间能量传递量子效率在受主浓度大约在N_A=0.6%时达到最佳值,并且明显地观测到浓度猝灭效应。     

Eu3+ luminescence and Gd3+-Eu3+ energy transfer in K5Li2GdF10:Eu3+

Polycrystalline samples of europium-doped K₅Li₂GdF₁₀ have been obtained by a slow cooling of melted compound and investigated using spectroscopy methods. Luminescence from the ⁵ D ₂ level of Eu³⁺ is found to be weak. Intense visible emission upon excitation into the ⁵ D ₂ or higher energy levels has been attributed to overlapping transitions from long-lived ⁵ D ₁ and ⁵ D ₀ levels. A strong increase of the ⁵ D ₀ emission at the expense of the ⁵ D ₁ emission occurs between 5 K and 25 K without significant change of the ⁵ D ₁ lifetime. To account for this, it is supposed that both the radiative and the nonradiative transition rates are temperature-dependent. Efficient energy transfer from the ⁶ G _J levels of Gd³⁺ to Eu³⁺ ions has been evidenced by excitation spectra in the VUV region and VUV-excited luminescence. It has been concluded that the cross relaxation contributes to the energy-transfer process. Received: 8 May 2001 / Accepted: 11 May 2001 / Published online: 25 July 2001     

GdBO3：Pr3+，Yb3+中Pr3+到Yb3+的能量传递及发光性质

采用高温固相法制备了一系列单掺或双掺Pr3+和Yb3+的GdBO3材料,分别测试分析了材料的物相结构和发光性质。在446 nm蓝光( Pr3+：3 H4→3 P2)激发下,检测到Yb3+的近红外特征发射,表明样品中存在Pr3+到Yb3+的能量传递。 Pr3+的掺杂浓度一定时,样品的发光会随着Yb3+掺杂浓度的改变而发生变化。通过对比不同掺杂情况下Pr3+：3 P0能级的衰减曲线,发现随着Yb3+的掺杂浓度的增加,该能级的荧光寿命不断缩短;同时利用不同条件下的衰减特性计算得出不同 Yb3+掺杂浓度样品的能量传递效率。用 Inokuti-Hirayama模型分析表明Pr3+-Yb3+能量传递类型为偶极子-偶极子相互作用。     

稀土掺杂铕(Ⅲ)二苯甲酰甲烷邻菲咯啉三元配合物的合成和荧光性质

合成了 3个系列稀土掺杂铕二苯甲酰甲烷 (Hdbm)邻菲咯啉 (phen)三元配合物 Eux RE1 -x(dbm) 3 phen(RE=La,Y,Gd;x=0 .0 0、0 .1 0、0 .30、0 .5 0、0 .70、0 .80、0 .90、1 .0 0 ) ,通过元素分析、摩尔电导率、红外光谱、X射线粉末衍射对配合物进行了表征。对各配合物系列进行荧光光谱研究 ,发现 L a3 、Y3 和 Gd3 对Eu3 离子均有荧光增敏作用 ,其荧光增敏顺序为 L a3 >Y3 >Gd3 。     

Photoluminescence of LiNbO3 crystals doped with Er3+ and Yb3+ ions

Results of cooperative phenomena investigations in the impurity subsystem of lithium niobate crystals doped with Er³⁺ and co-doped with Yb³⁺ impurity ions under continuous wave and pulsed excitation at 975 nm and 1064 nm wavelengths are presented. Dependences of some spectroscopic characteristics on the intensity of laser pumping are studied. Based on the pair centers model the analysis of the cooperative luminescence behavior in LiNbO₃:Yb³⁺+Er³⁺ crystals is performed.     

氟化物中Yb3+对Ho3+, Tm3+的直接敏化上转换作用

采用双掺杂(Yb^3 ／Ho^3 )和多掺杂(Ho^3 ／Yb^3 ／Tm^3 )方式,研究了氟化物中Yb^3 对Ho^3 ,Tm^3 的直接敏化上转换作用,并对它们在980nm激光激发下的上转换光谱特性进行了比较,对它们的上转换机理作了详细的讨论分析。观测到两处很强的上转换发光,分别是Yb^3 ／Ho^3 共掺杂体系中^5F4^5S2(Ho^3 )→^5Is(Ho^3 )的荧光跃迁和Ho^3 ／Yb^3 ／Tm^3 共掺杂体系中^3H4(Tm^3 )→H6(Tm^3 )的荧光跃迁。还发现由于添加了Tm^3 ,减弱了Yb^3 ／Ho^3 共掺杂体系中Ho^3 在可见光范围的上转换发光强度。     

ESR and superconductivity of Nd3+ and Gd3+ in ZrIr2

We report low temperatures ESR and Superconductivity experiments on Nd³⁺ and Gd³⁺ in the superconducting cubic intermetallic compound ZrIr₂. The ratio of the squares of the effective 4f-conduction electron exchange parameters corresponding to Nd³⁺ and Gd³⁺ ($\text{J}{}^2{}_{\mathrm{s-Nd}}\text{J}{}^2{}_{\mathrm{s-Gd}}$) were extracted both from the thermal broadening of the ESR linewidths and from the initial depression of the superconducting critical temperature, and were found to be comparable. Nd³⁺ was found to have a larger exchange parameter than of Gd³⁺.     

Spectroscopic and laser properties of Cr3+:Yb3+:Er3+: fluoride phosphate glass

Sensitization of the fluorescence of Er³⁺ in fluoride phosphate glass containing up to 20 mol% phosphates by codoping with Cr³⁺ and Yb³⁺ is shown. The low order of ligand field strength for Cr³⁺ (Dq/B=2.04) results in broad Cr³⁺ fluorescence overlapping the Yb³⁺ absorption. The electronic energy transfer efficiency approaches 100%. Deviations of donor decay from the Förster law are interpreted in terms of the inhomogeneously acceptor distribution. The electronic energy transfer efficiency of Yb³⁺ → Er³⁺ reaches a maximum value of 75% for glasses containing 20 mol% phosphates. The transfer is shown to be migrationally accelerated by means of GAF-LAF-FB theory. From Judd-Ofelt parameters a stimulated emission cross-section for the transition⁴I_13/2 →⁴I_15/2 of Er³⁺ of 6.2×10⁻²⁰ cm² is derived. The c.w. laser action of Er³⁺ by Cr³⁺ excitation and double-step energy transfer is shown. The output is tuned continuously from 1536 to 1596 nm. Flashlamp pumping is also shown.

     

掺杂镧、钇的铽(Ⅲ)乙酰丙酮三元配合物的合成及荧光性质研究

合成了四个系列稀土掺杂铽乙酰丙酮(Hacac)三元配合物RExTb1-x(acac)3phen和RExTb1-x(acac)3bipy(RE=La,Y;x=0,010,020,030,050,070,090,100;phen1,10邻菲罗啉;bipy2,2’联吡啶)。通过红外光谱、X射线粉末衍射对配合物进行了表征。对各系列配合物进行荧光光谱研究,发现La3+,Y3+对Tb3+离子均有荧光增敏作用,并且La3+>Y3+。当x=01～03,多数掺杂配合物比未掺杂铽三元配合物具有更好的发光性能。