Enhanced optical activation of Er in Er-doped Al2O3 powders by Y codoping in a sol-gel method

Enhanced photoluminescence (PL) mechanism of Er³⁺-doped Al₂O₃ powders by Y³⁺ codoping at wavelength 1.53 μm has been investigated through PL measurements of 0.1 mol% Er³⁺- and 0-20 mol% Y³⁺-codoped Al₂O₃ powders prepared at a sintering temperature of 900 °C in a non-aqueous sol-gel method. PL intensity and lifetime of Er³⁺-Y³⁺-codoped Al₂O₃ powders composed of γ-(Al,Er,Y)₂O₃ and θ-(Al,Er,Y)₂O₃ phases increased with increasing Y³⁺-codoping concentration. The 10-20 mol% Y³⁺ codoping in 0.1 mol% Er³⁺-doped Al₂O₃ powders intensified the PL intensity by about 20 times, with a PL lifetime prolonged from 3.5 to 5.8 ms. A maximal increase of the optical activity of Er³⁺ in 0.1 mol% Er³⁺-Y³⁺-codoped Al₂O₃ powders about one order was achieved by 10-20 mol% Y³⁺ codoping. It is found that the improved PL properties for Er³⁺-Y³⁺-codoped Al₂O₃ powders are mainly attributed to enhanced optical activation of Er³⁺ in the Al₂O₃ by Y³⁺ codoping, and to the slightly increased radiative quantum efficiency of Er³⁺ in the Al₂O₃.     

Infrared-to-visible upconversion in Er and Er/Yb activated Sb2O4 nanopowders prepared by sol-gel route

We prepared Er³⁺ doped and Er³⁺/Yb³⁺ codoped Sb₂O₄ nanocrystals by the sol-gel method. The Raman, X-ray diffraction (XRD), transmission electron microscope (TEM), and photoluminescence spectra of the samples were studied. The phonon energy of the Sb₂O₄ nanocrystals is very low (the maximum value being 461 cm⁻¹). The upconversion (UC) red emission of the Er³⁺/Yb³⁺ codoped sample is very strong at 975 nm laser diode excitation. The Sb₂O₄ nanocrystals will be a promising luminous material.     

Red, green and blue (RGB) emission doped Y3Al5O12 (YAG) phosphors prepared by non-hydrolytic sol-gel route

An evolutionary optimization process involving combination chemistry was employed in an attempt to develop Y₃Al₅O₁₂ (YAG). The combination chemistry process utilized here consisted the doping of the YAG host with appropriate amounts of red (R), green (G), and blue (B) dopants in a single layer, for use in tricolor white light. The doped YAG was acieved by means of the non-hydrolytic sol-gel route. Four samples were prepared, three of which were mono-doped samples containing 1.0% of a certain lanthanide (Eu³⁺, Tb³⁺, or Tm³⁺) ion, while the fourth contained the three ions. The samples were characterized by X-ray diffractometry and photoluminescence. The diffraction pattern of the mono-doped samples synthered at 800 °C for 16 h displayed peaks corresponding to the Y₃Al₅O₁₂ (YAG) phase, while the sample doped with the three ions revealed the presence of a mixture of Y₃Al₅O₁₂ (YAG) and Y₄Al₂O₉ (YAM) phases. The emission spectra of the three mono-doped YAG samples displayed the typical bands of the blue, green, and red emission of the corresponding lanthanide ions. As for the sample doped with the three lanthanide ions; it simultaneously emitted R, G and B lights. The green emission (546 nm) was more intense and narrow in relation to the red and blue emissions, which may be due to differences in the size of the three incorporated ions.     

Blue light emission from Eu ions in sol-gel-derived Al2O3-SiO2 glasses

Blue light-emitting glasses were successfully prepared by doping Eu²⁺ ions in the system Al₂O₃-SiO₂. The Al₂O₃-SiO₂ glasses doped with Eu³⁺ ions were synthesized using a sol-gel method, followed by heating in hydrogen gas atmosphere to reduce into the Eu²⁺ ions. The obtained glasses exhibited emission spectra with peak at ∼450 nm due to 4f⁶5d→4f⁷ (⁸S_7/2) transition, the intensities of which strongly changed depending on their glass composition and heating conditions. The emission quantum efficiency of 48% was achieved by heating the glass with the ratio of Al³⁺ to Eu³⁺ at about 6 at 1000 °C in hydrogen gas atmosphere. It was found that the Al₂O₃-SiO₂ glasses were appropriate not only for homogeneously doping the Eu³⁺ ions in glass structure but also reducing to Eu²⁺ ions, resulting in enhanced blue light-emission properties.     

Emission analysis of Pr and Tm: Ca2Gd2W3O14 phosphors

5 mol% of Pr³⁺ and Tm³⁺ ions activated calcium gadolinium tungstate (Ca₂Gd₂W₃O₁₄₎ phosphors were synthesized by traditional solid state reaction method. Crystalline phase structure was identified from the X-ray diffraction (XRD) profiles. From the scanning electron microscopy (SEM) images, we have observed the agglomeration of the particles, and average grain size is around 40-300 nm. Using the energy dispersive X-ray analysis (EDAX) and Fourier transform infrared (FTIR) spectra, identified the elements and functional groups present in the prepared phosphors. The emission spectrum of Pr³⁺: Ca₂Gd₂W₃O₁₄ powder phosphors have shown an intense red emission at 615 nm with the excitation wavelength λ_exci=450 nm and thus these red color emitting powder phosphors are used as one of the components in the preparation of WLEDs. The excitation spectrum of Tm³⁺: Ca₂Gd₂W₃O₁₄ powder phosphor has shown a ligand to metal charge transfer (W-O) band (LMCT) within the WO₄²⁻ group. Emission spectrum of Tm³⁺: Ca₂Gd₂W₃O₁₄ phosphors have shown blue emissions at 453 nm (¹D₂→³F₄).     

Up-conversion white light of Tm/Er/Yb tri-doped CaF2 phosphors

Tm³⁺/Er³⁺/Yb³⁺ tri-doped CaF₂ phosphors were synthesized using a hydrothermal method. The phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and up-conversion (UC) emission spectra. After annealing, the phosphors emitted white light under a 980 nm continuous wave diode laser (CW LD 2 W) excitation. As the excitation power density changed in the range of 20-260 W/cm², the chromaticity coordinates of the UC light of the phosphor Ca_0.885Tm_0.005Er_0.01Yb_0.1F₂ fell well in the white region of the 1931 CIE diagram. For the proportion of red, green and blue (RGB) in white light is strict, key factors for achieving UC white light, such as host materials, rare earth ions doping concentrations, annealing temperatures, as well as the excitation power densities, were investigated and discussed.     

Yb3+敏化的Er3+/Ho3+共掺碲酸盐玻璃的上转换发光研究

用高温熔融法制备了系列Er³⁺/Yb³⁺共掺，Ho³⁺/Yb³⁺共掺，和Er³⁺/Yb³⁺/Ho³⁺三掺碲酸盐玻璃，在975nm激光抽运下三种掺杂玻璃中都出现了较强的绿光和红光上转换.研究了Yb³⁺离子对Er³⁺和Ho³⁺离子上转换发光强度的影响以及Yb³⁺→Er关键词： 3+/Yb³⁺/Ho³⁺共掺')" href="#">Er³⁺/Yb³⁺/Ho³⁺共掺 碲酸盐玻璃 光谱性质 上转换     

Tm3+/Yb3+共掺碲酸盐玻璃的近红外发光及能量传递机理

采用高温熔融法制备了组分为TeO₂-ZnO-Na₂O的Tm³⁺离子单掺和Tm³⁺/Yb³⁺共掺碲酸盐玻璃,应用Judd-Ofelt理论计算分析了玻璃样品的强度参量Ω_t(t=2, 4, 6),自发辐射跃迁几率A,荧光分支比β和荧光辐射寿命τ_rad等光谱参量,测量得到了不同Yb³⁺离子掺杂浓度下玻璃样品的Tm³⁺离子上转换发光谱.结果显示,在980 nm泵浦光激励下玻璃样品发射出强烈的近红外上转换荧光.对Tm³⁺离子上转换发光分析表明,强烈的Tm³⁺离子近红外上转换发光主要来自于Yb³⁺/Yb³⁺离子间的共振能量传递以及基于单声子和双声子辅助的Yb³⁺/Tm³⁺离子间的非共振能量传递过程,并进一步计算得到了声子贡献比和能量传递系数.最后,计算分析了Tm³⁺:³F₄→³H₆能级间跃迁的1.8 μm波段吸收截面、受激发射截面和增益系数.研究表明,Yb³⁺/Tm³⁺共掺TeO₂-ZnO-Na₂O玻璃可以作为近红外波段固体激光器的潜在增益基质.     

Improvement of Er:I11/2→Ce:F5/2 energy transfer rate in Er/Ce co-doped TeO2-ZnO-Na2O-Nb2O5 glasses

The B₂O₃ component was introduced into Er³⁺/Ce³⁺ co-doped TeO₂-ZnO-Na₂O-Nb₂O₅ glass to improve energy transfer rate of Er³⁺:⁴I_11/2→Ce³⁺:²F_5/2 phonon-assisted cross-relaxation process. With the 6 mol% substitution of B₂O₃ for TeO₂, the energy transfer rate increased from 1300 to 1831 s⁻¹ and the fluorescence intensity increased by about 13.4%. However, the more B₂O₃ substitution in the same glass system reduced the quantum efficiency of Er³⁺:⁴I_13/2→⁴I_15/2 transition due to the higher OH⁻ group concentration. The results show that an appropriate amount of B₂O₃ component can be used to improve the phonon-assisted energy transfer rate and enhance 1.53 μm fluorescence emission by increasing the phonon energy of host glass. The effect of B₂O₃ on the energy transfer process, the lifetimes of the ⁴I_11/2 and ⁴I_13/2 levels, and the upconversion emission have also been investigated.     

Tm3+/Yb3+共掺氟氧硅铝酸盐玻璃陶瓷蓝色上转换发光研究

按摩尔百分比制备了组分为30SiO₂-(20-x-y)Al₂O₃-40PbF₂-10CdF₂-xTm₂O₃-yYb₂O₃的两组Tm³⁺/Yb³⁺共掺杂氟氧硅铝酸盐上转换蓝色发光玻璃陶瓷材料,测量了其在980nm激 关键词： 玻璃陶瓷 上转换发光 3+/Yb³⁺掺杂')" href="#">Tm³⁺/Yb³⁺掺杂 掺杂浓度     

Comparative investigation on spectroscopic properties of Er between Ce-doped and B2O3-added bismuth glasses

The comparative investigation on the spectroscopic properties of Er³⁺ in low phonon energy Bi₂O₃-GeO₂-Ga₂O₃-Na₂O glasses codoped with Ce³⁺ ion and added with B₂O₃ component, respectively, is presented. With increasing Ce₂O₃ content from 0 to 0.8 mol% or B₂O₃ content from 0 to 15 mol%, the lifetime of Er³⁺:⁴I_11/2 level decreases dramatically from 607 to 283 μs or to 197 μs, and the upconversion fluorescence is quenched in both glass samples. The nonradiative energy transfer from Er³⁺:⁴I_11/2→Ce³⁺:²F_5/2 or the enhanced multiphonon relaxation process together with the energy transfer between Er³⁺ and OH⁻ groups are, respectively, responsible for the results. Meanwhile, the lifetime of ⁴I_13/2 level remains almost unchanged in Er³⁺/Ce³⁺-codoped glasses whereas it decreases rapidly in B₂O₃-added cases. As a result, Er³⁺/Ce³⁺ codoping improves the 1.5 μm fluorescence emission intensity, however, B₂O₃ addition has a negative effect on it. The research results indicate that the Er³⁺/Ce³⁺-codoped bismuth glasses will be preferable for obtaining efficient 980 nm pumped EDFA.     

Up-conversion photoluminescence characteristics of Yb3+:Er3+:Tm3+ co-doped borosilicate glasses

Yb3+:Er3+:Tm3+ co-doped borosilicate glasses are prepared.Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared,which are excited by a 978-nm laser diode,are measured,and the mechanisms of energy transfer among Yb3+,Er3+ and Tm3+ ions are discussed.The results show that there is an unexpected wavelength at 900-nm emission from Yb3+ Stark splitting levels to pump Tm3+ ions and there exists an optimum pump power.The concentration of the Tm3+ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the Yb3+:Er3+:Tm3+ co-doped borosilicate glasses.     

Effect of Ce on the spectroscopic properties in Er doped TeO2-GeO2-Nb2O5-Li2O glasses

The Ce³⁺ ion was introduced into Er³⁺ doped TeO₂-GeO₂-Nb₂O₅-Li₂O (TGNL) glass to improve the 1.5 μm fluorescence characteristics. As increasing of Ce³⁺ concentration, the lifetime of Er³⁺:⁴I_11/2 level is shortened form 360 to 225 μs, while the Er³⁺:⁴I_13/2 level remains unchanged. Accordingly, the upconversion fluorescence (blue, green and red) was quenched. Improved 1.5 μm emission is obtained and the reason is ascribed to the increase of nonradiative rate between the ⁴I_11/2 and ⁴I_13/2 level of the Er³⁺ ions.     

White up-conversion emission in Ho/Tm/Yb tri-doped glass ceramics embedding BaF2 nanocrystals

Ho³⁺/Tm³⁺/Yb³⁺ tri-doped glass ceramics with white light emitting have been developed and demonstrated. Pumped by 980 nm laser diode (LD), intensive red, green and blue up-conversions (UC) were obtained. The green emission is assigned to Ho³⁺ ion and the blue emission is assigned to Tm³⁺ ion, whereas the red emission is the combination contribution of the Ho³⁺ and Tm³⁺ ions. The RGB intensities could be adjusted by tuning the rare-earth ion concentration and pump power intensity. Thus, multicolor of the luminescence, including perfect white light with CIE-X=0.329 and CIE-Y=0.342 in the 1931 CIE chromaticity diagram can be obtained in 0.15 Ho³⁺/0.2Tm³⁺/3Yb³⁺ tri-doped glass ceramics embedding BaF₂ nanocrystals pumped by a single infrared laser diode source of 980 nm at 500 mW. The up-conversion luminescence mechanism of Yb³⁺ sensitize Ho³⁺ and Tm³⁺ ions and the energy transfer from Ho³⁺ to Tm³⁺ in oxy-fluoride silicate glass ceramics were analyzed.     

Ce3+对Er3+/Yb3+共掺氟磷酸盐玻璃光谱性质的影响

研究了能量接受离子Ce³⁺对Er³⁺上转换发光强度以及Er³⁺在1.5μm附近波段发光性能参数的影响，并从能量匹配及能级结构角度出发对Er³⁺/Ce³⁺间的能量转移机制进行了分析.分析认为，⁴I_11/2能级的Er³⁺通过无辐射能量转移把能量传递给²F_5/2能级的Ce³⁺关键词： 氟磷酸盐玻璃 光谱性质 光纤放大器 3+和Ce³⁺')" href="#">Er³⁺和Ce³⁺     

Fluorescence enhancement of oxide fluoride glass co-doped with TbF3 and SmF3

The fluorescence property of xTbF₃-BaF₂-AlF₃-GeO₂+ySmF₃ (x=0.01-40 mol%, y=0-5 wt%) glasses were investigated. The enhancement of Sm³⁺ fluorescence was recognized in the presence of Tb³⁺. Increasing Tb³⁺ content, the emission color changed from green to orange. When the intensity of fluorescence at 540 nm originated from Tb³⁺ is compared with that at 600 nm originated from Sm³⁺, the information about the concentration quenching of Tb³⁺ and Sm³⁺ was obtained. From these results, rare earth ions were dispersed identically in the glasses. After heating to 673 K or cooling to 77 K, the emission color of 20TbF₃-20BaF₂-10AlF₃-50GeO₂/mol%+0.05 wt% SmF₃ glass was reversibly changed from orange to green. In addition, while the emission from 10TbF₃-20BaF₂-10AlF₃-60GeO₂+0.01 wt% SmF₃ glass was green, its crystallized sample, prepared by annealing at 1073 K, exhibited an orange emission due to Sm³⁺ at room temperature.     

The up-conversion properties of Yb and Er doped Y4Al2O9 phosphors

Er³⁺ doped and Yb³⁺/Er³⁺ co-doped Y₄Al₂O₉ phosphors are prepared by the sol-gel method. The effect of dopant concentration on the structure and up-conversion properties is investigated by X-ray diffraction (XRD) and photoluminescence, respectively. XRD pattern indicates that the sample structure belongs to monoclinic. Under 980 nm excitation, the green and red up-conversion emissions are observed and the emission intensities depended on the Yb³⁺ ion concentration. The green up-conversion emissions decrease with the increase of Yb³⁺ concentration, while red emission increases as Yb³⁺ concentration increases from 0 to 8 at% and then decreases at high Yb³⁺ concentration. The mechanisms of the up-conversion emissions are discussed and results shows that in Er³⁺ and Yb³⁺/Er³⁺ co-doped system, cross-relaxation (CR) and energy transfer (ET) processes play an important role for the green and red up-conversion emissions.     

Yb3+/Er3+共掺锗碲酸盐玻璃上转换发光增强机理的研究

玻璃的最大声子能量决定稀土离子的上转换发光强度，但本研究发现：Yb³⁺/Er ³⁺共掺锗碲酸盐玻璃在980nm LD抽运下，上转换荧光强度随着Bi₂O ₃对PbO的取代和碱 金属离子半径的增大而明显增强.而Raman光谱显示基质玻璃的最大声子能量并不随Bi ₂O₃对PbO的取代和碱金属离子半径的增大而变化，但玻璃的最大声子密 度随着Bi₂O₃对PbO 取代和碱金属离子半径的增大而降低.从玻璃无辐射跃迁概率的角度，通过分析表明，最大 声子密度的降低是玻璃上转换发光强度增强的主要原因.     

Er3+/Ce3+共掺碲铋酸盐玻璃的制备及光谱特性提高研究

采用高温熔融退火法制备了系列 80TeO₂-10Bi₂O₃-10TiO₂-0.5Er₂O₃-xCe₂O₃ (x=0,0.25, 0.5,0.75,1.0 mol%)和(80-y) TeO₂-10Bi₂O₃-10TiO₂-yWO₃-0.5Er₂O₃-0.75Ce₂O₃ (y=3,6,9,12 mol%)的碲铋酸盐玻璃.测试了玻璃样品400-1700 nm范围内的吸收光谱, 975 nm抽运下的上转换发光谱和1.53 μm波段荧光谱, 以及808 nm激励下的Er³⁺离子荧光寿命和无掺杂玻璃样品的Raman光谱, 并结合Judd-Ofelt理论和McCumber理论计算了Er³⁺离子光谱参数.结果表明, 在掺Er³⁺碲铋酸盐玻璃中引入Ce³⁺离子进行Er³⁺/Ce³⁺共掺, 通过Er³⁺离子⁴I_11/2能级与Ce³⁺离子²F_5/2 能级间基于声子辅助的能量传递过程,可以有效抑制Er³⁺离子上转换发光并明显增强其 1.53 μm波段荧光;同时,在现有Er³⁺/Ce³⁺共掺玻璃组分基础上引入WO₃, 可进一步提高1.53 μm波段荧光并展宽其荧光发射谱. 研究结果对于获取优异光谱特性的宽带掺Er³⁺光纤放大器玻璃基质具有实际意义.     

Role of Al coordination in barium phosphate glasses on the emission features of Ho ion in the visible and IR spectral ranges

The glasses of the composition (39−x)BaO-xAl₂O₃-60P₂O₅:1.0Ho₂O₃ (in mol%) with x value ranging from 1.0 to 4.0 have been synthesized. The IR spectral studies of these glasses have indicated that there is a gradual transformation of Al³⁺ ions from tetrahedral to octahedral with increase in the concentration of Al₂O₃ up to 3.0 mol%. Optical absorption and fluorescence spectra (in the visible and NIR regions) of these glasses have been recorded at room temperature. The Judd-Ofelt theory could successfully be applied to characterize the absorption and luminescence spectra of Ho³⁺ ions in these glasses. From the luminescence spectra, various radiative properties like transition probability A, branching ratio β_r, the radiative lifetime τ_r and emission cross-section σ^E for various emission levels of these glasses have been evaluated. The radiative lifetime of the ⁵S₂→⁵I₈ (green emission) transition has also been measured. The variations observed in these parameters have been discussed in the light of varying co-ordinations (tetrahedral and octahedral positions) of Al³⁺ ions in the glass network. The influence of hydroxyl groups on the luminescence efficiency of the transition ⁵S₂→⁵I₈ has also been discussed. Finally the optimum concentration of Al₂O₃ for getting maximum luminescence output has also been identified and reported.