Structural and spectroscopic characteristics of Eu3+-doped tungsten phosphate glasses

Tungsten based phosphate glasses are interesting non-crystalline materials, commonly known for photochromic and electrochromic effects, but also promising hosts for luminescent trivalent rare earth ions. Despite very few reports in the literature, association of the host́s functionalities with the efficient emissions of the dopant ions in the visible and near-infrared spectra could lead to novel applications. This work reports the preparation and characterization of glasses with the new composition 4(Sb₂O₃)96−x(50WO₃ 50NaPO₃)xEu₂O₃ where x = 0, 0.1, 0.25, 0.5 and 1.0 mol%, obtained by the melt quenching technique. The glasses present large density (∼4.6 g cm⁻³), high glass transition temperature (∼480 °C) and high thermal stability against crystallization. Upon excitation at 464 nm, the characteristic emissions of Eu³⁺ ions in the red spectral region are observed with high intensity. The Judd–Ofelt intensity parameters Ω₂ = 6.86 × 10⁻²⁰, Ω₄ = 3.22 × 10⁻²⁰ and Ω₆ = 8.2 × 10⁻²⁰ cm² were calculated from the emission spectra and found to be higher than those reported for other phosphate glass compositions. An average excited state lifetime value of 1.2 ms, was determined by fitting the luminescence decay curves with single exponential functions and it is comparable or higher than those of other oxide glasses.     

Gold nanoparticles assisted structural and spectroscopic modification in Er3+-doped zinc sodium tellurite glass

Achieving enhanced spectroscopic properties of rare earth doped inorganic glasses by embedding metallic nanoparticles of controlled sizes is a challenging task. We report the gold (Au) NPs assisted modifications in structural and spectroscopic properties of melt-quench synthesized Er³⁺ doped zinc sodium tellurite glass. The growth of NPs is stimulated via time varying heat treatment at 300 °C. XRD patterns confirm the amorphous nature of glasses and TEM images manifest the growth of gold NPs with sizes between 6.1 and 10.7 nm. The heat treatment time dependent variations in physical properties are ascribed to the alteration in bonding of non-bridging oxygen ions. The UV–VIS–NIR spectra reveal six absorption peaks centered at 488, 523, 655, 800, 973 and 1533 nm corresponding to the transition from ground state of ⁴I_15/2 to ⁴F_7/2, ²H_11/2, ⁴F_9/2, ⁴I_9/2, ⁴I_11/2, and ⁴I_13/2 excited states of Er³⁺ ions, respectively. Surface plasmon resonance (SPR) bands are observed in the range of 618–632 nm. Judd–Ofelt analyses demonstrate a significant increase of spectroscopic quality factors (0.86–1.05) and branching ratio (0.62–92.38%). The up-conversion emission spectra of Er³⁺ exhibit three prominent peaks of reasonable green (502 nm), a moderate green (546 nm) and a strong red (629 nm). An enhancement in the red band luminescence intensity by a factor of 8.19 and 8.54 times are achieved for 2 and 4 h of heat treatments, respectively. This enhancement is attributed to the SPR effects of gold NPs producing an intense local field in the proximity of Er³⁺ ions and subsequent energy transfer between RE ions and NPs. The FTIR spectra display the presence of vibrational modes for ZnO₄ bonds, Te–O bond in TeO₃ (tp) and TeO₄ (tbp) units and the hydroxyl groups. Excellent features of the results suggest that our method constitute a basis for tunable growth of gold NPs which is exceedingly useful for the optimization of optical and structural properties.     

Fluorescence properties of Eu3+-doped alumino silicate glasses

Alumino silicate glasses of a very broad range of molar compositions doped with 1 ⋅ 10²⁰ Eu³⁺ cm⁻³ (about 0.2 mol% Eu₂O₃) were prepared. As network modifier oxides Li₂O, Na₂O, K₂O, MgO, CaO, SrO, BaO, ZnO, PbO, Y₂O₃ and La₂O₃ have been used. All glasses show relatively broad fluorescence excitation and emission spectra. For most glasses only a weak effect of the glass composition on the excitation and emission spectra is observed. Although the glasses should be structurally similar, notable differences are found for the fluorescence lifetimes. These increase steadily with decreasing mean atomic weight, decreasing refractive index and decreasing optical basicity of the glasses, which may be explained by local field effects. An exception from this rule are the strontium, barium and potassium containing glasses, which show significantly increased fluorescence lifetimes despite of their high refractive index, optical basicity and molecular weight. The non mono-exponential fluorescence decay curves as well as the fluorescence spectra indicate a massive change in the local surroundings of the doped rare earth ions for these glasses.     

Spectroscopic evaluation of Zn(PO3)2:Dy3+ glass as an active medium for solid state yellow laser

A spectroscopic investigation of zinc phosphate glass activated with 1.0, 5.0 and 10.0 mol% of Dy(PO₃)₃ is performed through absorption and luminescence spectra and decay times to study its potentialities for yellow laser operation upon excitation at 399 nm, which fits to the requirements of GaN LEDs. In the 1.0 mol% Dy(PO₃)₃-doped glass a quantum efficiency of 80 ± 5% was estimated for the dysprosium ⁴F_9/2 level luminescence, the ⁴F_9/2 → ⁶H_13/2 yellow emission shows greater intensity than the ⁴F_9/2 → ⁶H_15/2 blue emission, as well as a very high optical gain, which might make this glass phosphor a promising gain medium for solid state yellow laser pumped by GaN LEDs.     

掺Er~(3+)重金属氧氟锗酸盐玻璃光谱性质研究

研究了重金属氧氟锗酸盐玻璃中Er3+离子的吸收光谱、有效吸收和发射线宽、荧光光谱、荧光半高宽、荧光寿命、带宽特性和增益性能.应用Judd-Ofelt理论计算了Er3+离子的强度参数Ωt(t=2,4,6),应用McCumber计算了能级4I13/2→4I15/2跃迁的吸收和受激发射截面.结果显示,随PbF2含量增加,Er3+离子的强度参数Ω6,吸收线宽、发射线宽、荧光半高宽、荧光寿命、带宽特性和增益性能都增加.表明掺Er3+重金属氧氟锗酸盐玻璃可作为宽带光纤放大器潜在的基质材料.     

Crystallization and spectroscopic properties in Er3+ doped oxyfluorogermanate glass ceramics containing Na

The Er³⁺ doped oxyfluorogermanate glasses, with a composition containing Na element, were synthesized by the conventional melting–quenching technique. When Na element was introduced into the composition of oxyfluorogermanate glass, the crystals behavior was investigated in details. Depending on the annealing procedure supplied, thermal annealing of precursor glasses in the system GeO₂/BaF₂/AlF₃/Na₂O/NaF/ZnO/GdF₃/ErF₃ led to the precipitation of different crystal phase nanocrystals. It was confirmed the nanocrystals in GC600 is orthorhombic NaBaAlF₆ which led to enhance obviously in the UC luminescence of Er³⁺. However, the nanocrystals in G585 led to decrease in the UC luminescence, which indicated few Er ions enter into the lattice of this nanocrystal phase. The reason of the decrease in UC emission intensity of GC585 was analyzed.     

掺Nd3+的镉硅酸盐玻璃的非线性光学特性

用高温熔融工艺制备了四种不同Nd3+掺杂浓度的镉铝硅酸盐玻璃样品,以纳秒Nd:YAG调Q激光器为光源,采用z-扫描技术研究了它们的非线性光学特性。结果表明,随着Nd3+浓度的增加,样品的非线性折射系数和非线性吸收系数也增加;光限幅测量表明,当入射功率密度大于118mW/mm2时,样品的透射功率密度与入射功率密度不再呈线性增加关系,而是随着入射功率密度的增加,透过率逐渐降低,透射功率密度增加缓慢,随着Nd3+浓度的增加,其光限幅效应显著增强。分析表明其光限幅效应是由反饱和吸收过程所致。     

Effect of divalent cations on properties of Er3+-doped silicate glasses

In order to design silicate glasses suitable as the host media for the Er³⁺ ions we studied a role of divalent cations (magnesium, calcium and/or zinc) on the properties of the glasses. In this study we focused on comparing the glasses from the point of view of their spectroscopic properties and feasibility to fabricate optical waveguides by ion exchange method as depended on optical basicity of the glasses. The calculated Judd–Ofelt parameters Ω_t corresponded well with the character of the bonding between erbium ions and surrounding oxygen ligands, i.e., changes of electron density caused by different divalent cations. The permeability of the glass structure for the diffusing ions studied using K⁺ and Ag⁺ ↔ Na⁺ ion exchange fabrication of optical waveguides showed that the covalent character of the glass makes its structure more opened for the penetrating particles. The results of the study revealed that addition of zinc had beneficial effect on the properties of glass for utilisation in optical amplifiers and waveguide lasers.     

Influence of mixed alkalis on spectroscopic parameters of Sm, Dy doped chloroborate glasses

This article reports the effect of mixed alkalis on the optical absorption and emission spectra of Sm³⁺ and Dy³⁺ doped chloroborate glass matrices of the compositions 69.5B₂O₃xLiCl(30 − x)NaCl0.5R₂O₃ and 69.5B₂O₃xLiCl(30 − x)KCl0.5R₂O₃ (where R = Sm and Dy and x = 5, 10, 15, 20 and 25). Using Judd-Ofelt theory, the spectral intensities and Judd-Ofelt intensity parameters (Ω_2,Ω₄ and Ω₆) were obtained from the measured absorption bands of the spectra. Using these intensity parameters, total radiative transition probabilities (A_T), radiative lifetimes (τ_R), branching ratios (β) and peak emission cross-sections (σ_P) were obtained for the two rare earth ions in these two glass matrices. Variation of these parameters with x in the glass matrix has been discussed. It is found that for Sm³⁺ ion, the transition, ⁴G_5/2 → ⁶H_9/2 shows highest emission cross-section and is maximum at x = 10 mol% in lithium-sodium and at x = 20 mol% in lithium-potassium glass matrices. For Dy³⁺ ion, the transition, ⁴F_9/2 → ⁶H_13/2 shows highest emission cross-section and is maximum at x = 20 mol% in lithium-sodium and at x = 10 mol% in lithium-potassium glass matrix.     

Spectroscopic analysis of a novel Nd3+-activated barium borate glass for broadband laser amplification

Spectroscopic parameters of a novel Nd³⁺-activated barium borate (BBONd) glass have been analyzed for broadband laser amplification. The Judd–Ofelt (JO) intensity parameters were determined through a systematic analysis of the absorption spectrum of Nd³⁺ ions in the BBONd glass. High values of the JO intensity parameters reveal a great centro-symmetrical loss of the Nd³⁺ sites and high covalency degree of the ligand field. The very high Ω₆ intensity parameter value makes evident both a great structural distortion of the Nd³⁺ sites and a strong electron–phonon coupling between Nd³⁺ and free OH⁻ ions, which is consistent with the phonon energy maximum (3442.1 cm⁻¹) recorded by Raman spectroscopy. This strong electron–phonon coupling favors high effective bandwidth and gain bandwidth values of the laser emission (⁴F_3/2 → ⁴I_11/2) of Nd³⁺ ions. The electric-dipole oscillator strengths of all the Nd³⁺ absorption transitions, and in particular that of the hypersensitive transition (⁴I_9/2 → ⁴G_5/2), are enhanced by this great structural distortion of the host. Broadband laser amplification of the ⁴F_3/2 → ⁴I_11/2 emission (1062 nm) of Nd³⁺ ions in the BBONd glass pumped at 805 nm (⁴I_9/2 → ⁴F_5/2 + ²H_9/2) is evaluated through the main fluorescent parameters in competition with non-radiative processes. In general, the BBONd glass exhibits spectroscopic parameters comparable with those reported in the literature for broadband laser amplification into the IR region.     

Optical absorption and fluorescence properties of Er3+ in sodium borate glass

Spectroscopic properties of Er³⁺ ions in sodium borate glass have been studied. The indirect and direct optical band gaps (E_opt) and energy level parameters (RacahE ¹, E² and E³), spin-orbit (ξ_4f) and configurational interaction (α)) are evaluated. Spectral intensities for various absorption bands of Er₃₊ doped sodium borate glass are calculated. Using Judd-Ofelt intensity parametersΩ ₂, Ω₄, Ω₆, radiative transition probabilities (A), branching ratios (β) and integrated absorption cross sections (Σ) are reported for certain transitions. The radiative lifetimes (τ_R) for different excited states are estimated. From the fluorescence spectra, the emission cross section (σ_P) for the transition,⁴I_13/2 → ⁴I_15/2 is reported.     

Ag+在硅酸盐玻璃中电场诱导扩散与纳米晶析出

利用直流电场诱导热扩散技术,引导金属银离子扩散进入硅酸盐玻璃基片内部,并通过后续热处理析出金属银纳米晶体。研究发现,随着电场强度的增大和扩散温度的升高,扩散进入到玻璃基片中的金属银离子数量也随之增多。电场诱导热扩散后银以Ag+和Ag0的形式存在于玻璃基片中。经后续热处理在玻璃基片中形成2～5nm的金属银纳米晶粒,并在410nm附近产生明显的表面等离子共振吸收现象;银纳米晶体主要分布在基片表面以下30～100μm区域。     

Impact of Nd3+ ions on physical and optical properties of Lithium Magnesium Borate glass

Enhancing the up-conversion efficiency of borate glass via optimized doping of rare earth ions is an ever-ending quest in lasing glass. Neodymium (Nd³⁺) doped Lithium Magnesium Borate (LMB) glasses are prepared using the melt-quenching method. X-ray diffraction (XRD), Fourier transformed infrared (FTIR), UV–Vis–NIR absorption and Photoluminescence (PL) spectroscopic characterizations are made to examine the influence of Nd³⁺ concentration on physical properties and optical properties. Nd³⁺ contents dependent density, molar volume, refractive index, ion concentration, Polaron radius, inter nuclear distance, field strength, energy band gap and oscillator strength are calculated. XRD patterns confirm the amorphous nature of all glasses and the FTIR spectra reveal the presence of BO₃ and BO₄ functional groups. UV–Vis–IR spectra exhibit ten prominent bands centered at 871, 799, 741, 677, 625, 580, 522, 468, 426, 349 nm corresponding to the transitions from the ground state to ⁴F_3/2, (⁴F_5/2 + ²H_9/2), (⁴F_7/2 + ⁴S_3/2), ⁴F_9/2, ²H_11/2, (⁴G_5/2 + ²G_7/2), (²K_13/2 + ⁴G_7/2 + ⁴G_9/2), (²G_9/2 + ²D_3/2 + ²P_3/2), (²P_1/2 + ²D_5/2), (⁴D_3/2 + ⁴D_5/2) excited states, respectively. A hyper-sensitive transition related to (⁴G_5/2 + ²G_7/2) level is evidenced at 580 nm. The room temperature up-conversion emission spectra at 800 nm excitation displays three peaks centered at 660, 610 and 540 nm. Glass with 0.5 mol% of Nd³⁺ showing an emission enhancement by a factor to two is attributed to the energy transfer between Mg²⁺ and Nd³⁺ ions. Our results suggest that these glasses can be nominated for solid state lasers and other photonic devices.     

Effect of Ce(Eu) codoping on the spectroscopic properties of Er in bismuth-germanate glass

In order to improve the transition rate from the ⁴I_11/2 level to the 1.53 μm fluorescence emitting ⁴I_13/2 level of Er³⁺, the Ce³⁺ and Eu³⁺ ions were respectively introduced into the Er³⁺ doped bismuth-germanate glass with a composition of Bi₂O₃–GeO₂–Ga₂O₃–Na₂O. The energy transfer mechanisms between Er³⁺ and the codopants were discussed based on their energy level diagrams. Though Ce³⁺ was less effective than Eu³⁺ on the decrease of the ⁴I_11/2 level lifetime, it hardly influenced the lifetime value of ⁴I_13/2 level. Both the ⁴I_11/2 and ⁴I_13/2 levels were depleted severely at the same time with the codoping of Eu³⁺. As a result, Er³⁺/Ce³⁺ codoping improved the 1.53 μm fluorescence emission intensity, while Er³⁺/Eu³⁺ codoping had a deleterious effect on it. The results indicate that the Er³⁺/Ce³⁺ is a preferable codoped scheme for bismuth-germanate glass with low phonon energy to obtain an efficient broadband EDFA pumped at 980 nm.     

Er~(3+)掺杂透明微晶玻璃光谱性质的研究

通过高温熔融法和热处理制备了含有-γBi2WO6纳米晶的Er3+掺杂透明硼铋酸盐微晶玻璃.根据X射线粉末衍射结果和Scherrer公式计算得到-γBi2WO6晶粒大小约为15 nm.由于部分Er3+离子取代Bi3+进入-γBi2WO6纳米晶相中,使得Er3+离子在1.5μm的有效发射带宽由78 nm增加到85 nm,同时Er3+离子在4I13/2能级的荧光寿命由0.67 ms增加到1.43 ms.此外,与原始玻璃相比,在Er3+掺杂硼铋酸盐微晶玻璃中观察到强烈的绿光上转换发光,其上转换发光机制可以归为双光子过程.     

Plasmon-enhanced luminescence of YAG: Yb, Er nanopowders by Ag nanoparticles embedded in silicate glass

Solid-state field-assisted diffusion was used to prepare Ag nano-composite silicate glass. After positive diffusion process, small Ag atoms clusters were formed in the slides. The Ag atom clusters could aggregate into Ag nanoparticles (NPs) with bigger size after subsequent reverse diffusion process. YAG: Yb, Er nanopowders were screen-printed on the glass slides after positive and reverse diffusion, respectively, for up-conversion luminescence measurement. Almost no luminescence enhancement was observed for the slide after positive diffusion. Whereas, obvious enhancement was obtained for the slide after reverse diffusion, and the enhancement factor could reach about 26. The strong enhancement was due to the larger size of Ag NPs. The present work suggested a new promising method to enhance the luminescence of YAG: Yb, Er nanopowders.     

Influence of Ga3+ ions on spectroscopic and dielectric features of multi component lithium lead boro bismuth silicate glasses doped with manganese ions

Multi-component glasses of the chemical composition 19.5Li₂O–20PbO–20B₂O₃–30SiO–(10 − x)Bi₂O₃–0.5MnO:xGa₂O₃ with 0 ≤ x ≤ 5.0 have been synthesized. Spectroscopic (optical absorption, IR, Raman and ESR) and dielectric properties were investigated. Optical absorption and ESR spectral studies have indicated that managanese ions do exist in Mn³⁺ state in addition to Mn²⁺ state in the samples containing low concentration of Ga₂O₃. The IR and Raman studies indicated increasing degree of disorder in the glass network with the concentration of Ga₂O₃ up to 3.0 mol%. The dielectric constant, loss and ac conductivity are observed to increase with the concentration of Ga₂O₃ up to 3.0 mol%. The quantitative analysis of the results of dielectric properties has indicated an increase in the insulating strength of the glasses as the concentration of Ga₂O₃ is raised beyond 3.0 mol%. This has been attributed to adaption of gallium ions from octahedral to tetrahedral coordination.     

Er3+掺杂弛豫铁电材料PMNT的单晶生长与性能表征

按照0.71Pb(Mg_1/3Nb_2/3)O₃-0.26PbTiO₃-0.03Pb(Er_1/2Nb_1/2)O₃化学式所示组分比例, 采用分步高温固相反应合成出Er³⁺掺杂PMNT多晶, 通过熔体坩埚下降法生长出尺寸φ25 mm×100 mm的Er³⁺掺杂PMNT晶体, Er³⁺离子以三元固溶体组元方式被掺杂进入钙钛矿相铁电体晶格; 测试了Er³⁺掺杂PMNT晶片的介电、压电与铁电性能以及上转换发光性能。结果表明, Er³⁺掺杂PMNT晶体呈现跟三方相纯PMNT晶体相近的介电、压电与铁电性能; 在980 nm激发光作用下, 该掺杂晶体呈现出Er³⁺离子特有的较强上转换荧光发射, 并且极化后掺杂晶体的上转换发光强度得到增强。     

Influence of Yb3+ and Ce3+ codoping on fluorescence characteristics of Er3+-doped fluoride glass under 980 nm excitation

Fluorescence characteristics of Yb³⁺:Ce³⁺:Er³⁺-codoped fluoride glasses is reported. Yb³⁺ codoping improved the excitation efficiency at 980 nm pumping and Ce³⁺ codoping improved the branching ratio of the Er^3+ 4I_11/2–⁴I_13/2 transition level, resulting in an enhancement in the fluorescence quantum yield at 1550 nm. The energy transfer dynamics of the Yb³⁺:Ce³⁺:Er³⁺-codoped fluoride glass was also analyzed based on a rate equation model. The separately measured energy transfer rates between Yb³⁺ and Er³⁺, and between Er³⁺ and Ce³⁺ agreed to some extent with the theoretical simulation based on the rate equation model at a lower Yb³⁺ concentration (<0.5 mol%).