Spectroscopic investigation of samarium-doped lead oxyflouroborate glasses using photo and cathode luminescence

Samarium-doped lead oxyflouroborate glasses of 60 B₂O₃- xPbO- (40-x)LiF where (x=0-30 mol%) with 3×10²⁰ ions/cm³ of Sm₂O_3, were prepared by melt quenching. UVVis absorption, photo luminescence (PL) and cathode luminescence (CL) spectroscopies were used to study the effect of varying PbO content on the spectroscopic properties of these samarium-doped glasses. The absorption of the UV-edge shifts toward higher wavelengths, not only because of higher polarizability of lead ions, but also because of the strong allowed s-p transition of Pb²⁺. Judd-Ofelts parameters were determined and indicate that the asymmetry around Sm³⁺ ions increases with increasing PbO content. Ω₂ probes the asymmetry by the ratio of intensity of the hypersensitive transition (⁶H_9/2) to that of purely magnetic (⁶H_5/2) transition. Furthermore, an increase in the spectroscopic quality factor (Ω₄/Ω₆) was observed with increasing PbO content which indicates that these glasses have the potential to be used as efficient active laser glasses. The calculated energy transfer parameter increases with increasing PbO content. Also, stark splitting increases with increasing PbO concentrations. FWHM of the CL emission peaks and stark splitting, are found to be much larger than that in PL. This was explained by the high electric field generated from the exciting electron pulses.     

An impact of sintering temperature and doping level on structural and spectral properties of Eu-doped strontium aluminium oxide

In the present work,a sol-gel method was employed to prepare nanosized SrAl2O4 powders doped with Eu3+ ions.The raw nano-materials were thermally treated at 900 to 1100 oC for 3 h.The XRD analysis demonstrated that the powders were single-phase nanopowders with high crystallite dispersion.Our studies were focused on relating the luminescence properties of the Eu3+ dopant to the NC(nanocrystal-lites) size.This was achieved by varying the calcinations temperature between 900 and 1100 oC.The average NC size varied accordingly be-tween ～36 and ～75 nm.We found that size effect manifested mainly in the expansion of the cell volume and broadening of XRD peaks as in-dicated by Rietveld analysis.Moreover the emission and excitation spectra,although typical for Eu3+ ions,demonstrated some degree of variability with calcinations temperature and doping concentration.To explain these differences a detailed analysis of luminescence spectra by the Judd-Ofelt theory was performed.     

Er3+/Yb3+共掺锗碲酸盐玻璃的热稳定性、 Judd-Ofelt理论分析和光谱性质

用高温熔融法制备了一种Er3 /Yb3 共掺的70TeO2-5Li2O-10B2O3-15GeO2玻璃.测试和分析了其热稳定性、吸收光谱、荧光光谱和上转换发光.应用Judd-Ofelt理论计算了玻璃中Er3 的强度参数、自发辐射跃迁几率、辐射寿命以及荧光分支比.结果表明:这种玻璃具有较好的热稳定性,较宽的荧光半高宽和较大的受激发射截面,位于532 nm、546 nm和659 nm的上转换绿光和红光,分别对应于Er3 离子2H11/2→4I15/2,4S3/2→4I15/2和4F9/2→4I15/2的辐射跃迁,是一种较为合适的宽带光纤放大器和上转换激光器的基质材料.     

掺铒TeO2-B2O3-Nb2O5-ZnO玻璃系统的光谱性质和热稳定性的研究

制备了碲酸盐玻璃样品70TeO2-(15-x)B2O3-xNb2O5-15ZnO-1wt%Er2O3(TBN,x=0,3,6,9,12,15 mol%).测试了玻璃样品的热稳定性和光谱性质.根据Judd-Ofelt理论计算了TBN玻璃中Er3 离子的强度参数(Ω2=(5.42～6.76)×10-20 cm2,Ω4=(1.37～1.73)×10-20cm2,Ω6=(0.70～0.94)×10-20 cm2),发现随着Nb2O5含量的增加,Ωt(t=2,4,6)先增加后减小.研究表明Er-O键共价性主要受基质玻璃中非桥氧数的影响,而阴阳离子间电负性的影响可以忽略.应用McCumber理论计算了Er3 离子的受激发射截面(σe=(0.77～0.91)×10-20 cm2)和Er3 离子4I13/2→4I15/2发射谱的半高宽度(FWHM=65～73 nm).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TBN玻璃系统具有较好的带宽性能,是一种制备宽带光纤放大器的潜在基质材料.     

Spectroscopic Properties and Judd-Ofelt Theory Analysis of Er^3＋-Doped Heavy Metal Oxyfluoride Silicate Glass

Er^3 -doped heavy metal oxyfluoride silicate glass was fabricated and characterized, and the absorption spectrum and fluorescence spectrum of the glass were studied. The Judd-Ofelt intensity parameters Ωt(t=2, 4, 6), spontaneous transition probability, fluorescence branching ratio and radiative lifetime of each energy levels for Er^3 were calculated by Judd-Ofelt theory, and stimulated emission cross-section of ^4I13/2→^4I15/2 transition was calculated by McCumber theory. The results show that fluorescence full width at half maximum and stimulated emission cross-section of Er^3 -doped heavy metal oxyfluoride silicate glass are broad and large, respectively. Compared with other host glasses, the gain bandwidth property of Er^3 -doped heavy metal oxyfluoride silicate glass is close to those of tellurite and bismuth glasses, and has advantage over those of silicate, phosphate and germante glasses.     

Er3 掺杂的碲硼酸盐玻璃的上转换光谱性质

研究了70TeO2-（15-x）ZnO-15Na2O-xB2O3-1wt％Er2O3（x=0、4、8、12和mol％）玻璃系统中B2O3的含量对Er^3＋上转换光谱性质的影响。结果表明：随B2O3含量的增加，Fr^31的^4 I11/2能级寿命减小；^4 I11/2→I13/2无辐射跃迁几率增加；Er^3＋的上转换绿光（^4S3/2、^2H11／2→I15/2）和红光（^4F9/2→4I15/2）减弱。基于Er^3＋在975nm波长激发下的上转换机理，建立了^4F7/2、^H11/2（^4S3/2）、^4H9/2、^4 I11/2和^4I13/2。这5个激发态能级的速率方程，结果表明，上转换绿光和红光强度跟^4 I11/2能级的粒子数的平方存在着正比关系。     

Up-Conversion Emission of Er3+ Ions in Yb3+ Sensitized Oxide Crystals

Most of the up-conversion lasers operated at room temperature are realized with heavy metal fluorides, In this paper the Judd-Ofelt parameters Ωλ ( λ = 2,4,6 ) were calculated for Er3+ ions in Yb3 + sensitized LiNbO3 and YVO4 crystals at room temperature, together with the radiative transition probabilities, non-radiative transition probabilities and resonant transition probabilities of Er3+ ions. Taking into account the energy transfer from Yb3 + to Er3 +, the rate equations are given for Er3 + ions. We obtained from a solution of the rate equations that Yb3 + sensitized YVO4 crystal is more efficient than Yb3 + sensitized LiNbO3 crystal in the up-conversion of 550 nm of Er3+ emission, which is consistent with our observation.     

Optical and Judd-Ofelt spectroscopic study of Er3+-doped strontium gadolinium gallium garnet single-crystal

Er³⁺-doped strontium gadolinium gallium garnet (SrGdGa₃O₇) single-crystal was grown by Czochralski method. The Er³⁺ concentration in the crystal was determined as 4.2 × 10²¹ ions/cm³ by inductively coupled plasma atomic absorption spectroscopy. Refractive index of the crystal was measured at the wavelengths of 633, 1311 and 1553 nm by prism coupling technique. The results show that the crystal is a positive uniaxial crystal with a birefringence of ~0.01, and the Sellmeier equation reported previously for the crystal doped with Nd³⁺ is also valid for the one doped with Er³⁺. Unpolarized absorption spectrum of the crystal was measured at room temperature and the Er³⁺ absorption cross-section spectrum was calibrated from it. The Er³⁺ spectroscopic properties were studied by Judd-Ofelt theory. Some fundamental spectroscopic parameters were obtained that include absorption coefficient and cross-section spectral distributions, electronic transition oscillator strength, Judd-Ofelt parameters, fluorescence branch ratio, transition probability, radiative and fluorescence lifetimes, and quantum efficiency.     

Ultraviolet radiation excited strong red-emitting LaAlO3:Eu3+ nanophosphors: Synthesis and luminescent properties

We synthesized the trivalent europium ions (Eu³⁺) doped lanthanum aluminate (LaAlO₃, LAO) nanophosphors by a solvothermal method. Their structural, morphological, and luminescent properties were systematically investigated. The obtained nanoparticles possessed single nanocrystallinity with a rhombohedral structure. For the excitation originating from the charge transfer band (O^2- to Eu³⁺ ions) under 320 nm illumination, the featured emissions of Eu³⁺ ions were detected in all the compounds. The optimum doping concentration of Eu³⁺ ions in LAO was about 9 mol% and the concentration quenching was dominated by dipole-dipole interaction. Furthermore, the Judd-Ofelt (J-O) theory was used to estimate the J-O intensity parameters. Based on the temperature-dependent PL emission spectra, the thermal stability was analyzed and the activation energy was obtained to be 0.234 eV. Meanwhile, the decay time, color coordinate/purity, and cathodoluminescence behaviors of the synthesized nanophosphors were also studied. These characteristics make the Eu³⁺-doped LAO nanoparticles a promising red-emitting phosphor for both ultraviolet-based white light-emitting diodes and field-emission displays.     

铒掺杂钠铝硅玻璃成分对其光谱性质的影响

研究了Na2O含量对Na2O-Al2O3-SiO2(NAS)玻璃的光谱性质的影响。利用Judd-Ofelt(J-O)理论和吸收光谱计算了Er^3 掺杂的铝硅酸盐玻璃的Ωt参数、自发辐射几率和自发辐射寿命，分析了Ωt参数与Na2O含量的关系以及与吸收截面，Er^3 离子^4I13 2能级的自发辐射几率和荧光半峰全宽(FWHM)等性质的关系。随Na2O含量的增加．J-O参数Ωt(t=2，4，6)减小，Er^3 离子1533nm的吸收截面和荧光半峰全宽．Er^3 离子^4I13 2能级的自发辐射几率也减小，而Er^3 离子的荧光寿命增大。