Synthesis and luminescence properties of Gd6MoO12:Yb3+, Er3+ phosphor with enhanced photoluminescence by Li+ doping

Yb³⁺/Er³⁺ co-doped Gd₆MoO₁₂ and Yb³⁺/Er³⁺/Li⁺ tri-doped Gd₆MoO₁₂ phosphors were prepared by adjusting the annealing temperature via the high temperature solid-state method. Under the excitation of 980 nm semiconductor, the upconversion luminescence properties were investigated and discussed. In the experimental process, we get the optimum Yb³⁺ concentration and the concentration quench effect will happen while the concentration extends the given region. According to the Yb³⁺ concentration quenching effects, the critical distance between Yb³⁺ ions had been calculated. The measured UC luminescence exhibited a strong red emission near 660 nm and green emission at 530 nm and 550 nm, which are due to the transitions of Er³⁺(⁴F_9/2, ²H_11/2, ⁴S_3/2) → Er³⁺(⁴I_15/2). Then the effect of excitation power density in different regions on the upconversion mechanisms was investigated and the calculated results demonstrate that the green and red upconversion is a two-photon process. A possible mechanism was discussed. After Li⁺ ions mixing, the upconversion emission enhanced largely, and the optimum Li⁺ concentration was obtained while fixed the Yb³⁺ and Er³⁺ on the above optimum concentration. This enhancement owns to the decrease of the local symmetry around Er³⁺ after Li⁺ ions doping into the system. This result indicates that Li⁺ is a promising candidate for improving luminescence in some case.     

Er3+单掺及Er3+/Yb3+共掺SiO2-Al2O3-La2O3玻璃光谱性质研究

研究了单掺Er³⁺及Er³⁺/Yb³⁺共掺SiO₂-Al₂O₃-La₂O₃玻璃的光谱性质随稀土离子浓度变化规律,应用McCumber理论计算了玻璃在1.53 μm的发射截面及积分吸收截面.结果表明:在Er³⁺离子掺杂浓度相同时,玻璃在980 nm吸收截面与Yb³⁺掺杂浓度成反比;当样品中Yb³⁺离子掺杂浓度为3.94×10²⁰ cm^-3时,玻璃在1.53 μm的吸收截面和发射截面最大,在1.40～1.60 μm积分吸收截面也最大;Er³⁺/Yb³⁺共掺SiO₂-Al₂O₃-La₂O₃玻璃在1.53 μm的荧光半高宽随Er³⁺掺杂浓度升高而增加,当Er³⁺离子掺杂浓度为2.41×10²⁰ cm^-3时,玻璃的荧光半高宽(FWHM)达到52.5 nm.     

Synthesis, characterization, optical absorption, luminescence and defect centres in Er3+ and Yb3+ co-doped MgAl2O4 phosphors

The Er³⁺–Yb³⁺ co-doped MgAl₂O₄ phosphor powders have been prepared by the combustion method. The phosphor powders are well characterized by X-ray diffraction (XRD) and energy dispersive (EDX) techniques. The absorption spectrum of Er³⁺/Er³⁺–Yb³⁺ doped/co-doped phosphor powder has been recorded in the UV–Vis–NIR region of the electro-magnetic spectrum. The evidence for indirect pumping under 980 nm excitation of Er³⁺ from Yb³⁺ was observed in the MgAl₂O₄ matrix material. Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the thermally stimulated luminescence (TSL) process in MgAl₂O₄:Er³⁺ phosphor. Three defect centres were identified in irradiated phosphor by ESR measurements which were carried out at room temperature and these were assigned to an O^? ion and F⁺ centres. O^? ion (hole centre) appears to correlate with the low temperature TSL peak at 210 °C and one of the F⁺ centres (electron centre) is related to the high temperature peak at 460 °C.     

Fabrication and luminescence behavior of phosphate glass ceramics co-doped with Er3+ and Yb3+

Transparent phosphate glass ceramics co-doped with Er³⁺ and Yb³⁺ in the system P₂O₅Li₂OCaF₂TiO₂ were successfully synthesized by melt-quenching and subsequent heating. Formation of the nanocrystals was confirmed by X-ray powder diffraction. Judd–Ofelt analyses of Er³⁺ ions in the precursor glasses and glass ceramics were performed to evaluate the intensity parameters Ω_2,4,6. Under 975 nm excitation, intense upconversion (UC) and infrared emission (1545 nm) were observed in the glass ceramics by efficient energy transfer from Yb³⁺ to Er³⁺. The luminescence processes were explained and the emission cross section was calculated by Fuchtbauer–Ladenburg (F–L) formula. The results confirm the potential applications of Er³⁺/Yb³⁺ co-doped glass ceramics as laser and fiber amplifier media.     

Upconversion emission enhancement in Er/Yb-codoped BaTiO3 nanocrystals by tridoping with Li ions

Er³⁺/Yb³⁺/Li⁺-tridoped BaTiO₃ nanocrystals were prepared by a sol-gel method to improve the upconversion (UC) luminescence of rare-earth doped BaTiO₃ nanoparticles. Effects of Li⁺ ion on the UC emission properties of the Er³⁺/Yb³⁺/Li⁺-tridoped BaTiO₃ nanocrystals were investigated. The results indicated that tridoping with Li⁺ ion enhanced the visible green and red UC emissions of Er³⁺/Yb³⁺-codoped BaTiO₃ nanocrystals under the excitation of a 976 nm laser diode. X-ray diffraction and decay time of the UC luminescence were studied to explain the reasons of the enhancement of UC emission intensity. X-ray diffraction results gave evidence that tridoping with Li⁺ ion decreased the local symmetry of crystal field around Er³⁺, which increased the intra-4f transitions of Er³⁺ ion. Moreover, lifetimes in the intermediate ⁴ S_3/2 and ⁴I_11/2 (Er) states were enhanced by Li⁺ ion incorporation in the lattice. Therefore, it can be concluded that Li⁺ ion in rare-earth doped nanocrystals is effective in enhancing the UC emission intensity.     

Blue upconversion luminescence of CaMoO4:Li+/Yb3+/Tm3+ phosphors prepared by complex citrate method

Li⁺/Tm³⁺/Yb³⁺ co-doped CaMoO₄ upconversion (UC) phosphor was prepared by complex citrate-gel method and UC luminescence properties were investigated. Li⁺/Tm³⁺/Yb³⁺ co-doped CaMoO₄ has intense blue emission induced by ¹G₄??³H₆ transition at 476?nm that is improved 10 times more than that of Li⁺ undoped sample and weak red emission at 647 nm generated by ³F₂??³H₆ transition under excitation at 980?nm. The optimum doping concentration of Li⁺ ions was investigated and UC mechanism of Li⁺/Tm³⁺/Yb³⁺ co-doped CaMoO₄ was discussed in detail.     

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.     

The influence of SiO2 content on spectroscopic properties and laser emission efficiency of Yb3+-Er3+ co-doped calcium aluminosilicate glasses

We have studied the influence of SiO₂ content on the spectroscopic properties and laser emission efficiency of Yb³⁺-Er³⁺ co-doped calcium aluminosilicate glasses. An increase in SiO₂ content resulted in higher phonon energy, which reduced the up-conversion emission, enhanced the energy transfer efficiency up to 70 % from Yb³⁺ to Er³⁺, and enhanced the optical quality. All these results led to an increase from 20 to 30 % in the laser emission efficiency.     

共沉淀法制备Y2SiO5∶Er3+ ,Yb3+ ,Tm3+及其上转换发光性能研究

采用化学共沉淀法制备了系列Y_1.98-2xYb_2x Er_0.02SiO₅(0.00≤x≤0.15)以及Y_1.736Yb_0.24Er_0.02Tm_0.004SiO₅上转换发光材料,比较了室温下Y_1.98-2xYb_2x Er_0.02 SiO₅ (x=0.00,0.08)样品在400—1600 nm范围内的吸收光谱,测量了所有样品在976 nm OPO激光器激发下的上转换发射光谱,以及Er³⁺离子⁴S_3/2(⁴F_9/2)→⁴I_15/2,Tm³⁺离子¹G₄→³H₆荧光衰减曲线和不同激发功率下的上转换蓝光发射强度,从而分析讨论了Er³⁺,Tm³⁺在Y₂SiO₅中的上转换发光机理.研究结果表明:在1250 ℃相对较低的温度下合成了X2型单斜晶系Y₂SiO₅ ∶Ln³⁺(Ln³⁺=Er³⁺,Yb³⁺,Tm³⁺),Yb³⁺的敏化显著增强了样品在976 nm附近的吸收能力,并大幅度加宽了该处的吸收带.分析上转换发射光谱发现:上转换绿光和红光强度都随着Yb³⁺浓度的增加先增强后减弱,但红光的猝灭浓度较高,归因于Er³⁺→Yb³⁺反向能量传递ETU4和Yb³⁺→Er³⁺正向能量传递ETU3过程的发生;上转换蓝光发射是三光子吸收过程,是通过Yb³⁺,Tm³⁺之间三次声子辅助的能量转移方式实现的. 关键词： 上转换 共沉淀 2SiO₅∶Er³⁺')" href="#">Y₂SiO₅∶Er³⁺ 3+')" href="#">Yb³⁺ 3+')" href="#">Tm³⁺     

The fluorescence properties of Yb3+ and Er3+ Co-doped YAl3(BO3)4 powders prepared by sol-gel method

Yb³⁺ and Er³⁺ co-doped YAB powders were prepared by sol-gel method. The structure and fluorescence properties were investigated. XRD pattern indicated that the single phase was obtained at 1150°C and the structure belonged to rhombohedral. Under 379 nm excitation, two emissions around 983 nm and 1531 nm were observed and the effect of Yb³⁺ ion concentration on the emission intensity was discussed. The energy transfer was observed under 930 nm excitation and the energy transfer efficiencies for all samples were calculated. The lifetimes of ² F _5/2 level of Yb³⁺ ion and ⁴ I _13/2 level of Er³⁺ ion were measured and the effect of Yb³⁺ ion concentration on the lifetime was also discussed. The results indicated that there was an additional mechanism for the decay of ⁴ I _13/2 level in powder samples. The Yb³⁺ and Er³⁺ co-doped YAB powders should be a potential candidate for ceramic laser materials.     

Er3+/Yb3+共掺的氧化镧钇透明陶瓷的光谱性能研究

采用传统无压烧结工艺制备了Yb³⁺/Er³⁺共掺的氧化镧钇透明陶瓷并对其光谱性能进行了研究.样品具有较大的吸收和发射截面.La₂O₃的添加使样品的荧光寿命(τ_s)与玻璃接近，当Yb³⁺和Er³⁺的掺杂量分别为5at%和0.5at%时，测得τ_s=9.65　ms.这种荧光寿命长、发射截面大和线宽窄的特性有利于微型、可集成化和大功率激光输出的实现. 关键词： 透明陶瓷 吸收光谱 发射光谱 荧光寿命     

Amplifying Characteristics of Er3+/Yb3+ Co-Doped Parallel-Cascaded Double Microring Resonators

Abstract

In terms of the coupled mode theory, formulas of the transfer function and the output power gain are presented for an Er³⁺/Yb³⁺ co-doped parallel-cascaded double microring resonator. Around the pump wavelength of 0.98 μm and the central signal wavelength of 1.55 μm, analysis is performed for the dependence of the output power gain on the pump power, signal power, dopant concentration, amplitude coupling ratio, and ring spacing. The results show that the output power gain of this device is much larger than that of the Er³⁺/Yb³⁺ co-doped waveguide amplifier with identical waveguide lengths. In the case of the amplitude coupling ratio κ = 0.064, ring spacing L₂ = 10π R, pump power P_p0 = 8 mW, signal power P_s0 = 37.2 μW, Er³⁺ ion concentration N_Er = 1 × 26 m^?3, and Yb³⁺ ion concentration N_Yb = 3 × 27 m^?3, the device can produce higher signal power gain from 11.9 dB even up to 70 dB.     

Crystalline-structure-dependent green and red upconversion emissions of Er-Yb-Li codoped TiO2

Crystalline structures and infrared-to-visible upconversion luminescence spectra have been investigated in 1 mol% Er³⁺, 10 mol% Yb³⁺ and 0-20 mol% Li⁺ codoped TiO₂ [1Er10Yb(0-20)Li:TiO₂] nanocrystals. The crystalline structures of 1Er10Yb(0-20)Li:TiO₂ were divided into three parts by the addition of Yb³⁺ and Li⁺. Both green and red upconversion emissions were observed from the ²H_11/2/⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions of Er³⁺ in Er³⁺-Yb³⁺-Li⁺ codoped TiO₂, respectively. The green and red upconversion emissions of 1Er:TiO₂ were enhanced significantly by Yb³⁺ and Li⁺ codoping, in which the intensities of green and red emissions and the intensity ratio of green to red emissions (I_green/I_red) were highly dependent on the crystalline structures. The significant enhanced upconversion emissions resulted from the energy migration between Er³⁺ and Yb³⁺ as well as the distortion of crystal field symmetry of Er³⁺ caused by the dissolving of Li⁺ at lower Li⁺ codoping concentration and the phase transformation at higher Li⁺ concentration. It is concluded that codoping with ions of smaller ionic radius like Li⁺ can efficiently improve the upconversion emissions of Er³⁺ or other rare-earth ions doped luminsecence materials.     

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.     

Optical parameters of Nd3＋：Er3＋：yb3＋ co-doped borosilicate glasses and their energy transfers at high temperature

This paper reports that a series of Nd³⁺:Er³⁺:Yb³⁺ co-doped borosilicate glasses have been prepared and their absorption spectra measured. The J--O intensity parameters Ω_k (k=2, 4, 6), spontaneous radiative lifetime τ_rad, spontaneous transition probability A, fluorescence branching ratio β and oscillator strength f_ed of the Nd³⁺ ions at room temperature are calculated based on Judd--Ofelt (J--O) theory. The temperature dependence of the up-conversion photoluminescence characteristics in a Nd³⁺:Er³⁺:Yb³⁺ co-doped sample is studied under a 978 nm semiconductor laser excitation, and the energy transfer mechanisms among Yb³⁺, Er³⁺ and Nd³⁺ ions are analysed. The results show that the J--O intensity parameters Ω₂ increase when the Nd³⁺ concentration of the Nd³⁺:Er³⁺:Yb³⁺ co-doped borosilicate glasses increases. The possibility of spontaneous transition is small and lifetimes are long at levels of ⁴F_5/2 and ⁴F_3/2. The intensity of Nd³⁺ emissions at 595, 691, 753, 813 and 887 nm are markedly enhanced when the sample temperature exceeds 400 K. The reasons being the cooperation of the secondary sensitization from Er³⁺ to Nd³⁺ and the contribution of a multi-phonon.     

Enhancement of the upconversion photoluminescence intensity in Li and Er codoped Y2O3 nanocrystals

Infrared-to-visible upconversion luminescence spectra are investigated in Li⁺ and Er³⁺ codoped Y₂O₃ nanocrystals. By introducing Li⁺ ions, the upconverted emission intensity is found to be greatly enhanced when compared with the nanocrystals with the Li⁺ absent. The cause of the enhancement is believed to be the modification of the local symmetry of the Er³⁺ ion, which increases the intra-4f transitions of Er³⁺ ion, and the homogeneous distribution of Er³⁺. While in some other Er³⁺ doped oxides, such as ZnO, ZrO₂, etc., the upconversion intensity of Er³⁺ ions could also be greatly increased by doping Li⁺.     

Avidin conjugation to up-conversion phosphor NaYF4:Yb3+, Er3+ by the oxidation of the oligosaccharide chains

NaYF₄:Yb³⁺, Er³⁺ nanoparticles were successfully prepared by a polyol process using diethyleneglycol (DEG) as solvent. After being functionalized with SiO₂–NH₂ layer, these NaYF₄:Yb³⁺, Er³⁺ nanoparticles can conjugate with activated avidin molecules (activated by the oxidation of the oligosaccharide chain). The as-formed NaYF₄:Yb³⁺, Er³⁺ nanoparticles, NaYF₄:Yb³⁺, Er³⁺ nanoparticles functionalized with amino groups, avidin conjugated amino-functionalized NaYF₄:Yb³⁺, Er³⁺ nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR), UV/Vis absorption spectra, and up-conversion luminescence spectra, respectively. The biofunctionalization of the NaYF₄:Yb³⁺, Er³⁺ nanoparticles has less effect on their luminescence properties, i.e., they still show the up-conversion emission (from Er³⁺, with ⁴S_3/2 → ⁴I_15/2 at ~540 nm and ⁴F_9/2 → ⁴I_15/2 at ~653 nm), indicative of the great potential for these NaYF₄:Yb³⁺, Er³⁺ nanoparticles to be used as fluorescence probes for biological system.     

Judd–Ofelt analysis and upconversion emission of Er3+–Yb3+ co-doped oxyfluoride glass ceramics containing LaF3 nanocrystals

Er³⁺–Yb³⁺ co-doped glasses and glass ceramics containing LaF₃ nanocrystals were prepared and their absorption spectra obtained. The Judd–Ofelt parameters Ω _t (t?=?2,?4,?6) for f–f transition of Er³⁺, as well as spontaneous emission probabilities, branching ratios and radiative lifetimes for stimulated emission of each band were determined. Addition of Er³⁺ and Yb³⁺ ions into low-phonon energy LaF₃ nanocrystals makes the upconversion emission of Er³⁺–Yb³⁺ co-doped glass ceramic much stronger than that of Er³⁺–Yb³⁺ co-doped glass.     

Green,blue, red,near-infrared up-conversion luminescence of Yb<Superscript>3+</Superscript>/Er<Superscript>3+</Superscript>/Tm<Superscript>3+</Superscript> co-doped YVO<Subscript>4</Subscript> nanoparticles

YVO₄:Yb³⁺,Er³⁺; YVO₄:Yb³⁺,Tm³⁺; and YVO₄:Yb³⁺,Er³⁺,Tm³⁺ were all synthesized via sol-gel method with a subsequent thermal treatment. Specifically, YVO₄:Yb³⁺,Er³⁺,Tm³⁺ phosphors were prepared with different annealing temperatures to study the influence of temperature. The transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffractometer (XRD), and photoluminescent (PL) spectrofluorometer were used to investigate the morphology, crystal structure, and up-conversion luminescent properties of all samples. In summary, all samples were granular-like nanoparticles and well crystallized with the same tetragonal phase as YVO₄. Under the irradiation at 980 nm, YVO₄:Yb³⁺,Er³⁺ phosphors can generate green emission at 525 and 553 nm and red emission at 657 nm, while YVO₄:Yb³⁺,Tm³⁺ phosphors can generate blue emission at 476 nm, red emission at 648 nm, and near-infrared emission at 800 nm. Notably, YVO₄:Yb³⁺,Er³⁺,Tm³⁺ samples can exhibit green emission, blue emission, red emission, and near-infrared emission at the same time, which might endow the as-prepared samples with potential applications in many fields, such as luminous paint, infrared detection, and biological label.     

Er3+，Er3+/Yb3+掺杂氟化镧超微材料的光谱特性与上转换发光

采用共沉淀法制备了Er³⁺掺杂和Er³⁺/Yb³⁺共掺杂LaF₃超微材料,所制备的样品的颗粒呈球形,尺寸为250nm左右.计算得到Er³⁺单掺杂样品中对应着⁴S_3/2和⁴F_9/2能级的发光量子效率分别为67.0%和71.9%.研究发现,随着Yb³⁺离子浓度的增加 关键词： 3+')" href="#">Er³⁺ 3+')" href="#">Yb³⁺ 发光 能量传递