Effects of substitution of BaF2 for GdF3 on optical properties of dense oxyfluoride borogermanate scintillating glasses

Eu3+-activated B2O3-GeO2-37Gd2O3-3Eu2O3-(15–x)GdF3-xBaF2 (0≤x≤15) scintillating glasses with the density of 6.1–6.3 g/cm3 were synthesized by a melt-quenching method. The substitution of BaF2 for expen...     

Novel Tm-doped fluorotellurite glasses with enhanced quantum efficiency

In this paper, new highly Tm³⁺-doped tellurite glasses with host composition 75TeO₂-xZnF₂-yGeO₂-12PbO-3Nb₂O₅ [x(5-15), y(0-5) mol%] are presented and compared to the Tm-doped tellurite glasses based on the traditional host composition: 75TeO₂-20ZnO-5Na₂O mol%. Enhanced quantum efficiency from ³F₄ level was observed for the proposed glasses and thermal stability and viscosity values make them suitable for optical fiber drawing. Besides the host composition, substantial influence of Tm³⁺ concentration on luminescence and lifetime of excited ³F₄ and ³H₄ states were discussed.     

Spectral properties of Ho:GdVO4 single crystal

Absorption and emission spectral properties of GdVO₄ single crystal doped with Ho³⁺ ions were investigated at room temperature. Polarized absorption cross section is calculated in the range of 400–2200 nm. Results were analyzed and parameters were calculated based on Judd-Ofelt theory, the emission spectrum shows that the emission intensity around the wavelength of 546 nm associated with transition ⁵S₂ → ⁵I₈ is much stronger than other bands in the observed range and potentially enable the green light output around this emission band in this crystal.     

Influence of In3＋ ions concentration on spectroscopic properties of Ho：LiNbO3 crystals

In:Ho:LiNbO3 crystals doped with various concentrations of In3+(0, 1 mol.%, 3 mol.%, 5 mol.%), fixed concentrations of Ho3+ (1 mol.%) were grown by Czochralski method. The X-ray powder diffraction, infrared and UV-visible absorption spectra were measured and modified. Judd-Ofelt approach was employed to study the effect of In doping on spectroscopic properties of Ho:LiNbO3 crystals. In concentrations in crystals were analyzed by an inductively coupled plasma optical emission spectrometry (ICP-OE/MS). For In (3 mol.%):Ho (1 mol.%):LiNbO3 crystal, the obtained intensity parameters were: Ω2=9.6563, Ω4=4.2195, Ω6=14.1526. The results showed that the Ω2 and Ω6 parameters increased with the increase of In3+ concentration. When the In doping concentration was up to 5 mol.%, Ω2 and Ω6 suddenly decreased. In2O3 incorporation had a strong effect on the radiative lifetime, but had less influence on fluorescence branching ratios. The effective distribution coefficient of In3+ in In:Ho:LiNbO3 crystals was less than 1 and increased with increasing concentration of In3+ in the melt.     

Electrospinning preparation and luminescence properties of Eu(TTA)3phen/polystyrene composite nanofibers

Efficient luminescent composite nanofibers,composed of polystyrene(PS,Mw=250000) and europium complex Eu(TTA)3phen(TTA=2-thenoyltrifluoroacetone,phen=1,10-phenanthroline) with diameters ranging from 350 nm to 700 nm,were prepared by electrospinning and characterized by scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FT-IR),fluorescence spectroscopy,and thermogravimetric analysis(TG).The room-temperature fluorescence spectra of the composite nanofibers were composed of the typical Eu3+ ion red emission,assigned to the transitions between the first excited state(5D0) and the multiplet(7F0-4).Owing to the incorporation of the europium complex into the PS fiber matrix and the subsequent distortion of the symmetry around the lanthanide ions by the capping PS,the polarization of the Eu3+ ions was enhanced,which increased the probability for electronic dipole allowed transitions.The monochromaticity(5D0→7F2/5D0→7F1) around the Eu3+ ions was also efficiently improved.Judd-Ofelt intensity parameters(Ω2 and Ω4) were determined from the emission spectra based on the 5D0→7F2 and 5D0→7F4 electronic transitions,respectively.The results showed that the Ω2 values of the composite nanofibers were apparently higher than that of the pure complex,indicating an increased covalency degree in the europium first coordination shell due to the modification of PS matrix.The modification of the polymer matrix also resulted in much higher thermal stability of the composite fibers than that of the pure complex.     

Luminescent properties of a new Nd3+-doped complex with two different carboxylic acids and pyridine derivative

A new Nd3+-doped organic complex featuring two different perfluorinated carboxylic acids as the first ligand and pyridine derivative 2-amino-3-chloro-5-(trifluoromethyl)pyridine as the second ligand was designed and synthesized.Successful coordination between the ligands and central rare earth ions was confirmed by Fourier transform infrared spectroscopy(FT-IR)spectra,1H nuclear magnetic resonance(1H NMR)spectra,and UV spectra,and the synthesized complex is inferred to be eight-coordinate structure.Solution of the complex dissolved in DMSO-d6 was prepared and then its fluorescence spectrum,UV–Vis–NIR absorption spectrum,and fluorescence decay curve were tested.The fluorescent lifetime is about 7 ls.Based on the above experimental research,Judd–Ofelt analysis was carried out,and the results indicate that appropriate coordination environment around Nd3?in this solution results in a high fluorescent quantum efficiency 2%and a large stimulated emission cross-section about 3.2 9 10-20cm2at 1,064 nm.     

Synthesis and optical properties of Eu~(3+) ion doped nanocrystalline hydroxya patites embedded in PMMA matrix

Transparent,luminescent and functional nanocomposites demonstrate interesting optical and mechanical properties suitable for many optoelectronic applications.Transparent polymethyl methacrylate(PMMA) polymer nanocomposites modified with thenoyl-trifluoroacetonate(TAA) were fabricated by in situ polymerization and used as hosts for homogenous dispersion of 3 mol.% Eu3+:Ca10(PO4) 6(OH) 2(Eu3+:HA) hydroxyapatite ～20 nm large nanocrystals.The emission,excitation and transmission spectra as well as the fluorescence decay rates of bare Eu3+:HA nanocrystallites,Eu3+:HA embedded in the PMMA and and Eu:HA embedded in the PMMA/TTA nanocomposites were studied.The improvement of transparency was demonstrated with the addition of TTA as well as europium doped hy-droxyapatites in comparison to pure PMMA matrix.The Judd-Ofelt analysis of f-f transitions of Eu3+:HA nanocrystallites,the PMMA/Eu3+:HA and the PMMA+TTA/Eu3+:HA was performed to investigate the optical behavior of the polymeric composites.     

掺铒碲酸盐玻璃的热力学稳定性和光谱性质的研究

分析了掺Er³⁺碲酸盐玻璃的热力学稳定性能,研究了掺Er3+碲酸盐玻璃的吸收和荧光光谱性质;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^-20cm², Ω₄=1.52×10^-20cm²,Ω₆=0.66×10^-20_cm2),计算了离子的自发跃迁几率,荧光分支比;应用McCumber理论计算了Er3+的受激发射截面(σ_e=10.40×10^-21cm²)、Er³⁺离子⁴I_13/2→⁴I_15/2 发射谱的荧光半高宽(FWHM=65.5nm)及各能级的荧光寿命(⁴I_13/2能级为τ_rad=3.99ms);比较了不同基质玻璃中Er3+离子的光谱特性,结果表明掺铒碲酸盐玻璃更适合于掺Er³⁺光纤放大器实现宽带和高增益放大.     

Spontaneous emission in the ellipsoidal nanocrystals

The equation was presented for the spontaneous emission rate A_nano of the two-level optical centers in the subwavelength ellipsoidal nanocrystals embedded in a dielectric medium. An important result was that the ratio A_nano/A_bulk could be estimated without recourse to a particular local-field model. On the ground of this equation the expression was derived for linestrength of electric-dipole transition in trivalent rare-earth ions. The applicability of the Judd-Ofelt equation for nanoparticles was discussed.     

Tm:YAP激光晶体光谱参数的计算

采用丘克劳斯基(Czochralski)法生长了Tm:YAP晶体,研究了该晶体在室温下的吸收光谱和荧光光谱.结果表明,Tm:YAP晶体在689.5 nm和795 nm左右有较强的吸收峰,分别对应于3H6→3F3和3H6→3H4的能级跃迁,半峰全宽(FWHM)分别为22.5 nm和30 nm,吸收截面分别为1.89×10-20 cm2和1.35×10-20 cm2.荧光光谱表明Tm:YAP晶体发射波长为1.89μm,相应的荧光寿命为13.90 ms,发射截面为1.58×10-19 cm2.根据乍得-奥菲特(Judd-Ofelt)理论计算了Tm3+在Tm:YAP晶体中的强度参数:Ω2=1.4560×10-20cm2,Ω4=2.0673×10-20 cm2,Ω6=0.3181×10-20 cm2.结果表明,Tm:YAP晶体具有宽的吸收峰、长荧光寿命和较大的积分发射截面的性质,非常适合于激光二极管(LD)抽运,有利于获得低阈值高效率的2μm波段激光输出.