Tb3+掺杂的氟氧碲酸盐玻璃发光性能

用高温熔融法制备了Tb³⁺掺杂的氟氧碲酸盐玻璃样品,测试了不同Tb³⁺和Gd³⁺浓度玻璃样品的密度、透过光谱、以及380 nm紫外光和X射线激发的发光光谱.着重研究了玻璃中不同Tb³⁺和Gd³⁺离子含量对玻璃性能的影响规律及机理.结果表明:氟氧碲酸盐玻璃具有较大的密度,ρ大于5 g/cm³;增加Tb³⁺离子的浓度,可以有效提高样品的闪烁发光 关键词： 铽离子 氟氧碲酸盐玻璃 闪烁玻璃 发光性能     

Composition dependent structural and optical properties of Sm doped boro-tellurite glasses

Boro-tellurite glasses with the composition (69-x)H₃BO₃+xTeO₂+15MgCO₃+15K₂CO₃+1Sm₂O₃ (where x=0, 10, 20, 30 and 40 wt%) doped with trivalent samarium have been prepared and their structural and spectroscopic behavior were studied and reported. The FTIR spectra reveal the presence of BO₃ and BO₄ non-bridging oxygen as well as strong OH⁻ bonds in the prepared glasses. Through the optical absorption spectra, Judd-Ofelt intensity parameters (Ω_λ, λ=2, 4 and 6) have been evaluated and the same is in turn used to predict radiative properties such as radiative transition probability (A), stimulated emission cross-section () and branching ratios (β_R) for the excited levels of Sm³⁺ ions corresponding to ⁴G_5/2→⁶H_5/2, ⁴G_5/2→⁶H_7/2, ⁴G_5/2→⁶H_9/2 and ⁴G_5/2→⁶H_11/2 transitions. Structural and spectral dependence of the Sm³⁺ ions due to the compositional changes have been examined and reported. The lifetime of the ⁴G_5/2 level is found to be non-exponential for all the prepared glasses indicating a cross-relaxation among the Sm³⁺ ions. The structural and spectroscopic results corresponding to compositional changes have been compared with the similar studies and reported.     

Effect of ZnO as modifier on up and downconversion properties of Ho/Yb doped tellurite glasses

Optical absorption and photoluminescent properties of Ho³⁺/Yb³⁺ co-doped tellurite and zinc tellurite glasses are investigated. The effect of zinc oxide as a modifier on the luminescence properties of above mentioned samples has been explored. Two intense upconversion emission bands centered at 546 (⁵F₄ + ⁵S₂ → ⁵I₈) and 660 nm (⁵F₅ → ⁵I₈) are observed on excitation with 976 nm diode laser. Zinc oxide acts as a quencher for 976 nm excited upconversion emission. The up and downconversion emission spectra are recorded with 532 nm excitation source also. In this case zinc oxide improves the up and downconversion emissions. A large enhancement in upconversion intensity has been observed when Ho³⁺ ion is co-doped with Yb³⁺ ion. The dependence of upconversion intensities on excitation power and on temperature has also been studied. The power dependence study shows a quadratic dependence of the fluorescence intensity on the excitation power while a decrement in emission intensity of all the transitions at different rates with increase in temperature is observed in temperature dependence study. The possible mechanisms are also discussed in order to understand the upconversion and energy transfer processes.     

Spectroscopy of thulium and holmium heavily doped tellurite glasses

In this study, we report spectroscopic properties of Tm³⁺ and Ho³⁺ codoped tellurite glasses over a wide dopant concentration range in order to assess their potential laser performance under 790 nm diode laser excitation. The impact of Tm³⁺ and Ho³⁺ concentrations is investigated to identify specific candidates for fiber laser operation. The emission cross section is calculated and discussed, as well as the gain coefficient of this type of glasses. Energy transfer microparameters and critical ion distances are determined for ³H₄, ³F₄ (Tm³⁺), and ⁵I₇ (Ho³⁺) emission levels in the framework of diffusion-limited regime and dipole–dipole interaction. We also report thermal properties of tested glasses.     

Europium doped strontium borate glasses and their optical properties

Optical absorption and luminescence spectra of europium doped strontium borate glasses prepared in different conditions are studied. It is found that the percentage of Eu³⁺ ions varies from 100 to 30% being controlled by the conditions of preparation. The mechanism, favoring reduction of europium to Eu²⁺ state in polycrystalline strontium tetraborate, is much weaker in glasses of the same composition. In samples containing mixed valence europium at densities of 8×10²⁰ cm⁻³, the efficient transfer of optical excitation from Eu³⁺ to Eu²⁺, suppressing the Eu³⁺ luminescence, has been found. The most reliable way of monitoring the percentage of europium ions in different valences for strontium borate glasses is the measuring of absorption at f-f transition ⁷F₀→⁵D₂ of Eu³⁺.     

Improving dosimetric properties of tellurite glasses

Thermoluminscence (TL) properties of quaternary tellurite glass in the form 80(TeO₂)–5(TiO₂)–(15−x)(WO₃)–(x)A_nO_m where A_nO_m=Nb₂O₅, Nd₂O₃, Er₂O₃ and x mol% have been measured. TL main dosimetry peak for each produced glass sample were investigated for ⁶⁰Co gamma rays. Dosimetric properties of the quaternary tellurite glasses have been measured as a function of different compositions of the glass system in different rare earth oxides concentration by using thermoluminescence (TL) detection technique.     

Piezooptical effects in the tellurite glasses doped by europium and gold

We present the temperature dependence of piezooptical coefficients for three samples of TeO₂-GeO₂-PbO glasses doped with 0.5% of Eu₂O₃, 0.5% and 1% of Au₂O₃, after different thermoannealing times. We have established that there exist two temperatures singularities - minima in the range 655-695 K and maxima - at 850 K. It is crucial that for the glasses annealed during 61 h, at temperatures about 850 K, the anomaly of piezooptical coefficient disappears. Simultaneously the minima within the range 655-695 K changed depending on the duration of the thermoannealing which leads to low temperature shift of the minima. Towards lower temperature the piezooptical maxima occurs around 850 K and disappears after the increase of the annealing time. It is also crucial that the values of the piezooptical coefficients decrease with the enhancement of the thermoannealing. The observed temperature dependence with the piezooptical coefficients has a good correlation with the temperature dependences of the DSC. We have found that the pure glasses and glasses doped only by Au₂O₃ and Eu₂O₃ possess the piezooptical coefficients one order less with respect to the samples possessing simultaneously Au₂O₃ and Eu₂O₃.     

Evaluation of optical parameters of some tellurite glasses

Evaluation of optical parameters of tellurite glasses in the form: 80TeO₂-5TiO₂-(15-x) WO₃-xA_nO_m, where xA_nO_m = 0.01, 1, 3, 5 Nb₂O₅ or 0.01, 0.1, 1, 3 Nd₂O₃ or 0.01, 0.1, 1, 3, 5, 7 Er₂O₃ mol% will be carried out. The optical parameters will be focused on calculating molar refractivity, molar polarizability, oxide ion polarizability, molar cation polarizability, optical basicity, metallization and number of polarizable atoms per unit volume for every glass composition in order to interpret the refractive index of these glasses.     

Optical,physical and structural studies of boro-zinc tellurite glasses

To investigate the modification effect of the modifier ZnO on boro-tellurite glass, a series of glasses with compositions 50B₂O₃–(50?x)ZnO–xTeO₂ have been prepared by conventional melt quenching technique. Amorphous nature of the samples was confirmed through X-ray diffraction technique. Optical absorption and IR structural studies are carried out on the glass system. The optical absorption studies revealed that the cutoff wavelength increases while optical band gap (E_opt) and Urbach energy decreases with an increase of ZnO content. Refractive index evaluated from E_opt was found to increase with an increase of ZnO content. The compositional dependence of different physical parameters such as density, molar volume, oxygen packing density, optical basicity, have been analyzed and discussed. The IR studies showed that the structure of glass consists of TeO₄, TeO₃/TeO₃₊₁, BO₃, BO₄ and ZnO₄ units.     

Nonlinear optical properties of erbium doped zinc oxide (EZO) thin films

Undoped and Erbium (Er) doped zinc oxide (EZO) thin films were deposited on glass substrate by sol–gel method using spin coating technique with different doping concentration. EZO films were characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), UV–VIS-NIR transmission and single beam z scan method under illumination of frequency doubled Nd:YAG laser. The deposited films were found to be well crystallized with hexagonal wurtzite structure having a preferential growth orientation along the ZnO (002) plane. A blue-shift was observed in the band gap of EZO films with increasing Er concentration. All the films exhibited a negative value of nonlinear refractive index (n₂) at 532 nm which is attributed to the two photon absorption and weak free carrier absorption. Third order nonlinear optical susceptibility, χ⁽³⁾ values of EZO films were observed in the remarkable range of 10^? 6 esu. EZO (0.4 at.%) sample was found to be the best optical limiter with limiting threshold of 1.95 KJ/cm².     

Influence of high-temperature treatment on the structure and emission properties of opal doped with erbium

The influence of high-temperature treatment of opal—erbium composites on their spectral properties in the wavelength region of 1.5 μm is investigated, the dependence of the luminescence intensity on the erbium concentration is measured, and the structure of the composite after high-temperature treatment is examined using transmission electron microscopy. The regular structure of the composites undergoes considerable transformations up to the complete loss of periodicity upon annealing at a temperature of 1500 K for 10 h and more. The composites in this case are sintered into a homogeneous substance. Pores disappear, and erbium oxide inclusions in the form of 30- to 70-nm regular solid spheres are observed instead. Measurements of the luminescence spectra in the wavelength region of 1.5 μm for the opal-erbium composites with erbium oxide concentrations in the range 0.25–16.00 wt % have shown that the luminescence yield reaches the maximum at an Er₂O₃ content of 1 wt % in the composite. Analysis of the influence of the temperature and time of heat treatment on the luminescence intensity of the samples has revealed a nonmonotonic character of the dependence on the annealing time for all the temperatures under investigation. The factors responsible for this behavior are discussed. The reflection spectra of the opal-Er₂O₃(1 wt %) composites after heat treatment have demonstrated that the photonic band gap of the samples degrades at annealing temperatures of 1300 K and higher. A method proposed for retaining the periodic structure upon heat treatment consists in introducing the stabilizing phase into the opal.     

Luminescence properties of ytterbium and erbium doped silica-zirconia nanostructured optical fiber under near infrared excitation

We present here the luminescence properties of erbium and ytterbium doped silica-zirconia nanostructured optical fibers prepared by the chemical sol-gel method. After describing the preparation process, their waveguiding properties as well as luminescence properties under continuous pumping in the near infrared domain (NIR) are reported; the effects of the zirconia nanocrystals that are dispersed in the core of the fibers on their optical properties are finally discussed.     

Spectroscopic and optical properties of Nd doped fluorine containing alkali and alkaline earth zinc-aluminophosphate optical glasses

Nd³⁺ doped fluorine containing zinc-aluminophosphate glasses have been prepared with alkali and alkaline earth content to understand the effect of network modifiers on radiative process. The physical and optical properties of these glasses have been evaluated. The Judd-Ofelt model for the intensity analysis of induced electric dipole transitions has been applied to the measured oscillator strengths of the absorption bands to determine the three phenomenological intensity parameters Ω₂, Ω₄ and Ω₆ for each glass. Using these parameters, transition probability (A), total transition probability (A_T), branching ratios (β_R) radiative life times (τ_R) and integrated cross-section (σ_a) for the stimulated emission have been theoretically calculated for certain excited Nd³⁺ fluorescent levels. From the obtained results the conclusion is made about the possibility of using these glasses as laser material.     

Effect of Li2O content on physical and structural properties of vanadyl doped alkali zinc borate glasses

The effect of Li₂O content in vanadyl doped 20ZnO+xLi₂O+(30−x)Na₂O+50B₂O₃ (5≤x≥25) glasses has been studied with respect to their physical and structural properties. The absence of sharp peaks in XRD spectra of these glass samples confirms the amorphous nature. The physical parameters like density, refractive index, ionic concentration and electronic polarizability vary non-linearly with x mol% depending on the diffusivities of alkali ions. EPR and optical absorption spectra reveal that the resonance signals are characteristics of VO²⁺ ions in tetragonally compressed octahedral site. Spin-Hamiltonian, crystal field, tetragonal field and bonding parameters are found to be in good agreement with the other reported glass systems. The tetragonal distortion (g_⊥-g_∥) and Dt reveals that their values vary non-linearly with Li₂O content and reaches a minimum at x=10 mol%. An anomaly of character has been observed in all the properties of vanadyl doped glass systems, which gives a clear indication of mixed alkali effect.     

Analysis on the optical properties for the ytterbium doped silica glasses prepared by laser sintering technology

The paper demonstrates the optical properties of the ytterbium doped silica glasses that were fabricated by laser sintering technology combined with liquid phase doping method, and analyzed the influence of the fabricated process on the formation of Yb²⁺. The spectral parameters and laser performance parameters were also calculated and analyzed. The results indicate that the formation of Yb²⁺ can be effectively restrained through the optimized preparation process. The prepared ytterbium doped silica glass presents typical absorption and emission cross sections of Yb³⁺, and possesses attractive laser performance parameters. The material would have potential applications for the gain medium of large mode area photonic crystal fiber lasers.     

Cathodoluminescent and nonlinear optical properties of undoped and erbium doped nanostructured ZnO films deposited by spray pyrolysis

We have deposited zinc oxide (ZnO) and erbium doped zinc oxide (ZnO:Er) thin films on heated glass substrates using spray pyrolysis technique. The effect of erbium dopant on structural, morphological, luminescent and nonlinear optical properties was studied. The deposited films have been analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), ex situ compositional analysis (ESCA), profilometry, cathodoluminescence (CL) and third harmonic generation (THG) measurements. All films were polycrystalline, having a preferential growth orientation along the ZnO (0 0 2) plane, with a corresponding average crystallite size of less than 41 nm. Addition of erbium can effectively control the film surface morphology and its cathodoluminescent properties. The films containing low erbium concentration show a uniform surface covered with hexagonal shaped grains and a strong UV light emission intensity as well as TH response. In contrast, when the erbium doping ratio exceeds 3%, a porous surface with columnar textural growth becomes more pronounced, and a substantial reduction of the cathodoluminescent and TH response. A strong TH signal was obtained for the film with good crystalline quality at the concentration of 2%. Third order nonlinear optical susceptibility (χ^〈3〉) values of the studied materials were in the remarkable range of 10⁻¹² esu.     

Electron paramagnetic resonance, optical and electrical properties of vanadyl doped alkali germanoborate glasses

Glasses with composition xGeO₂.(0.30−x)M₂O.0.70B₂O₃ (M=Li, K) containing 2.0 mol% of V₂O₅ have been prepared in the range 0.00≤x≤0.15 by normal melt quenching method. Electron paramagnetic resonance (EPR), optical transmission and absorption spectra and dc conductivity of these glasses have been studied. Spin Hamiltonian parameters (SHPs) of VO²⁺ ions, dipolar hyperfine coupling parameter, P, Fermi contact interaction parameter, K and molecular orbital coefficients (α² and γ²) have been calculated. In GeO₂·Li₂O·B₂O₃ glasses there is no change in the tetragonality of the V⁴⁺O₆ complex and the size of 3d_xy orbit also remains unchanged with increase in GeO₂ content. In GeO₂·K₂O·B₂O₃ glasses, there is an increase in the tetragonality of the V⁴⁺O₆ complex and the 3d_xy orbit expands with increase in GeO₂ content. Values of the theoretical optical basicity, Λ_th, have also been reported. Optical band gap decreases with increase in GeO₂ content. The dc conductivity of these glasses decreases and the activation energy increases with increase in GeO₂:M₂O ratio.     

Effect of erbium concentration on optical properties of Er:YLF laser crystals

Four Er-doped LiYF₄ crystals with different Er-concentrations were grown by Czochralski method. The laser crystals were characterized by measurements of ICP-AES, XRD, absorption spectra, up-conversion fluorescence spectra, near-infrared (NIR) and mid-infrared (Mid-IR) fluorescence spectra, as well as luminescence decays. It was found that the heavily 15 at% Er-doped YLF crystal is more proper in up-conversion or ∼3 μm laser applications; while the 5 at% Er-doped YLF is a better candidate for ∼1.5 μm lasers within these four crystals.     

Effect of metal fluorides on chromium ions doped bismuth borate glasses for optical applications

Fluoride based glasses with composition CaF_2-ZnF_2-Bi_2 O_3-B_2 O_3 doped with chromium ions have been investigated using physical, optical, electron paramagnetic resonance(EPR), Fourier-transform infrared spectroscopy(FTIR), and Raman studies. The amorphous nature of samples was confirmed from x-ray diffraction spectra. The density is evaluated from the Archimedes principle and the values of optical band gap and Urbach energy values were evaluated from the optical absorption spectra. Thus, molar volume, refractive index, etc., were also evaluated. The observed decrease in density and the optical band gap with CaF2 is explained using the crystalline density of metal fluorides and the ionicity of fluorine ions,respectively. The three peaks near 450 nm, 606 nm, and 720 nm, which are shown in the absorption spectra, are accredited to ~4 A)(2 g) → ~4 T_(1 g), ~4 A_(2 g)→ ~4 T_(2 g), ~4 A_(2 g)→~2 E transitions, respectively. Resonance signals at g≈ 4.82 and g≈ 1.99 were observed in EPR spectra which are assigned. FTIR and Raman analysis were carried out to examine the impact of metal fluorides on the structure of bismuth borate glasses.     

The optical properties of thin erbium films

The effective dielectric constant, ε′₂, of very thin films of erbium on sodium chloride substrates was determined from measurements of normal incidence reflectance and transmittance in the visible spectrum. ε′₂ showed a maximum which moved to longer wavelengths as the film thickness increased. Electron microscopy revealed that the film islands grew flatter and more irregular with thickness. The shape factor of the islands, F, was calculated by a modified Maxwell-Garnett method and became smaller as the film thickness increased.