Doped Silicate Glasses Research Articles

Quenching behavior of Sm3+ doped lanthanum aluminosilicate glasses

In this paper we report on the fluorescence quenching behavior of Sm3+ doped lanthanum alumino silicate glasses in dependence of the Sm3+ concentration and chemical composition of the glasses. In general, lanthanum alumino silicate glasses offer relatively low intrinsic Sm3+ fluorescence lifetimes between 2.3 and 2.7ms. Independently on the doping concentration, the lifetime decreases with increasing refractive index and increasing lanthanum concentration of the glasses. For a low doping concentration of 0.1×1020 Sm3+ per cm3 (approx. 0.025mol% Sm2O3) the measured fluorescence lifetimes are very close to the radiative lifetimes which were calculated using the Judd–Ofelt analyses. For higher doping concentrations, such as 1×1020 and 3×1020 Sm3+ per cm3, concentration quenching becomes obvious. For these higher concentrations, the non-radiative relaxation of the excited state can be seen as a mixture of cross-relaxation processes and OH− quenching. Both processes mainly occur at higher concentrations and do not influence the fluorescence decay at low Sm3+ concentrations. By contrast, the maximum phonon energy of the glass network does not affect the radiative relaxation of Sm3+ at all.

Phosphor in glass with Eu3+ and Pr3+-doped silicate glasses for LED color conversion

Phosphor-in-glasses (PiGs) with rare earth (RE) doped SiO2–B2O3–RO glasses were prepared by embedding YAG:Ce3+ as the yellow phosphor. Eu3+ and Pr3+ were used to dope the glass, varying their concentrations in order to provide red emissions for possible chromaticity-control of white-light emitting diodes (WLEDs). The glass-to-phosphor mixing ratio was also varied to find the proper combination for color-controlled white LEDs. PiGs with RE-doped glasses were sintered at 750°C and polished to 250μm in thickness for blue LED color conversion. The photoluminescence spectra of the PiGs were monitored after they were mounted on commercial blue LED chips. Variation of color coordination, color rendering index and correlated color temperature were observed due to red emissions from the doped RE-ions. The spectral contribution of Eu3+ and Pr3+ ions to white LEDs under 450nm LED excitation was discussed. The spatial distribution of phosphors within the glass matrix, and their possible interaction, was inspected by SEM. The thermal quenching effect was also investigated.

~2 µm Luminescence properties and nonradiative processes of Tm3+ in silicate glass

Two novel Tm3+-doped silicate glasses (one with fluoride addition) with good thermal stability were prepared in this work. Luminescence properties of these two samples were compared. After the addition of fluoride, the luminescence intensity of 1.8µm was much improved whereas that of 1.47µm was reduced. The rates of nonradiative processes populating and depopulating 3F4 were calculated quantitatively and a new method of calculating the quenching rate of hydroxyls was proposed. It was found that multiphonon relaxation rate of 3F4→3H6 was really low and could be neglected in both samples. The addition of fluoride in glass could reduce the quenching rate of hydroxyls but raised the cross-relaxation (3H6+3H4→3F4+3F4) rate. Thus the quantum efficiency of 1.8µm luminescence was improved after the introduction of fluoride.

Doping transition metal ions as a method for enhancement of ablation rate in femtosecond laser irradiation of silicate glass

We present a doping method to improve the femtosecond laser ablation rate and promote ablation selectivity. Doping transition metal ions, Co2+ or Cu2+, in silicate glass apparently change absorption spectroscopy and induce resonant absorption at wavelengths of 600 and 800 nm, respectively. Comparing with femtosecond laser processing of the same glass without doping, we find that the threshold fluence decreases and the ablation rate increases in resonant absorption in doped silicate glass. Resonant absorption effectively increases multiphoton ionization for seed-free electron generation, which in turn enhances avalanche ionization.

基质对Tb3+单掺荧光玻璃发光性质的影响

Tb3 +doped borate,silicate and phosphate glasses and glass matrixes were prepared by high temperature melting technology. According to the UV-Vis transmission spectra,the experiment oscillator strengths of Tb3 +from7F6to5D3and5D4were calculated,and the luminescent properties of Tb3 +in different glass matrixes were explained. The results show that the 542 nm and 585 nm emissions of Tb3 +doped in phosphate glass have split into two peaks because of the poor symmetry. In borate and silicate glasses,the particles in5D3energy level of Tb3 +have been emptied and moved to5D3energy level because of the cross relaxation,so the emissions from5D3energy level(413,436 nm) are not obvious. In phosphate glass,5D3energy level of Tb3 +has much fewer particles and no cross relaxation,so the emission from5D3energy level is the strongest. The characteristic emission peaks of Tb3 +from5D4energy level are 489,542,585 and 620 nm. In different glass matrixes,the order of their intensities from largest to smallest is borate,silicate and phosphate glass,which is consistent with the order of experiment oscillator strengths from7F6to5D4.

On the Conduction Mechanism of Silicate Glass Doped by Oxide Compounds of Ruthenium (Thick Film Resistors). 3. The Minimum of Temperature Dependence of Resistivity

This article is the final part of the investigation of conduction mechanism of silicate glass doped by oxide compounds of ruthenium (thick film resistors). In the first part [1], the formation of percolation levels due to diffusion of dopant atoms into the glass has been considered. The diffusion mechanism allowed us to explain shifting of the percolation threshold towards to lower value and the effect of firing conditions as well as the components composition on the electrical conduction of the doped glass. The coexistence of thermal activation and localization of free charge carriers as the result of nanocrystalline structure of the glass was the subject of the second part [2]. Because of it, the resistivity of the doped silicate glass is proportional to exp (–aT–ζ) at low temperatures (T 50 K), 0.4 ζ T > 800 K) and the conductivity of the doped silicate glass decreases sharply. We consider the origin of the minimum in the temperature dependence of resistivity of the doped silicate glass here. It is shown that the minimum arises from merge of impurity band into the valence band of glass at temperature high enough, so thermal activation of charge carriers as well as its hopping are failed, and scattering of free charge carriers become predominant factor in the temperature dependence of the resistivity.

Effect of Tm2O3 concentration and hydroxyl content on the emission properties of Tm doped silicate glasses

Tm2O3-doped multi-component silicate glasses without alkali ions are prepared using a conventional melt quenching method. The Judd–Ofelt theory is applied to calculate the intensity parameters of the resultant glass. The intensity parameters of silicate glasses without alkali ions are larger than those of silicate glasses with alkali ions. The spontaneous radiation probability of the transition from 3F4 to 3H6 of glasses without alkali ions is 191.89s−1, which is larger than that of glasses with alkali ions. Moreover, the measured lifetime of the 3F4 energy level of glasses is larger too. Emission cross section results show a maximum value 3.89×10−21cm2 at 1882nm. These findings indicate that the glass in this study can be used to realize ~2μm lasers. The effect of variations in Tm2O2 concentration on the emission properties is also studied. Cross-relaxation and emission intensity enhance with increasing Tm2O3 content. However, the lifetime of the 3F4 level decreases because of concentration quenching. The influence of OH groups on the emission properties is also investigated.

Fluorescence and radiative properties of Nd3+ ions doped zinc bismuth silicate glasses

Abstract Glasses having composition 20ZnO⋅ x SiO 2 ⋅(79.5− x )Bi 2 O 3 ⋅0.5Nd 2 O 3 with x varying from 10 to 50 mol% have been synthesized. The amorphous nature of the glasses was confirmed by X-ray diffraction studies. Optical absorption and fluorescence spectra were measured at ambient temperature. This paper reports on different physical and absorption spectral properties of Nd 3+ doped zinc bismuth silicate glasses with varying content of Bi 2 O 3 to understand its influences on hypersensitive band intensities. From the recorded absorption spectra, Judd–Ofelt intensity parameters Ω λ = ( λ = 2, 4, 6) have been evaluated with their quality factors and are used to compute the radiative properties of Nd 3+ glasses. The calculated Judd–Ofelt parameters are found to decreasing with decrease in Bi 2 O 3 content in the glass which may be due to the decrease in Nd–O bond covalency. From these intensity parameters various radiative properties like spontaneous emission probability ( A rad ), radiative life time ( τ r ), fluorescence branching ratio ( β r ) and stimulated emission cross-section ( σ ) for various emission bands have been calculated. The stimulated emission cross-section of fluorescence transition 4 F 3/2 → 4 I 11/2 have high values and varies from 15.19 × 10 −20 cm 2 to 5.73 × 10 −20 cm 2 with Bi 2 O 3 content in the host glass. The results point out this glass system as good candidate to be used in the development of photonics devices operating in the near infrared spectral range. Further, the FTIR results reveal that the glasses have BiO 6 , SiO 4 and non-bridging oxygen as local structure.

Single-mode waveguides generated in Nd3+-doped silicate glass by nickel ion irradiation

Single mode waveguide in Nd3+-doped silicate glass substrate was fabricated by ion implantation technique. Nd3+-doped silicate glass is irradiated with 3MeV Ni ions at a fluence of 5×1014ions/cm2. The prism-coupling method is used to measure the effective refractive indices of the waveguide dark modes. Only one mode is found, in which its effective index (neff=1.5207) is higher than the substrate index (nsub=1.5202). The refractive index distribution of the waveguide was reconstructed; and the near-field intensity distribution is in a good agreement with simulated modal profiles. Propagation losses of the light in the waveguides were measured by the back-reflection method. It is found that after annealing the propagation loss of waveguide is effectively reduced.

Bismuth silicate glass as host media for some selected rare-earth ions and effects of gamma irradiation

Ultraviolet, visible and infrared spectral measurements were used to investigate prepared undoped and rare-earth doped (2.5%) bismuth silicate glasses (80% Bi2O3–20%SiO2) before and after being subjected to gamma irradiation (8 Mrad). The base bismuth silicate glass reveals strong extended UV–near visible absorption bands which are attributed to the presence of trace iron impurities in the raw materials together with absorption due to sharing of Bi3+ ions. The RE-doped samples show the same strong UV–near visible bands as the undoped glasses beside extra narrow characteristic bands mostly in the visible and near-infrared regions due to the respective studied rare-earth ions. The base undoped and all RE-doped samples except CeO2 sample reveal quite resistance to the effect of gamma irradiation due to heavy atomic mass Bi3+ ions present in high content (80%) and the rare-earth ions are known to be weakly affected due to the known 5s, 5p shielding. The exceptional effect of CeO2-doped sample is related to the ability of Ce3+ ions to change its oxidation state through photochemical reaction by irradiation or exchange with Fe3+ present as trace iron impurities. The FT infrared spectra of the prepared glasses reveal characteristic absorption bands which are related to the silicate groups together with the sharing of vibrational modes due to Bi–O groups. The IR spectra are slightly affected by gamma irradiation indicating the stability of the structural network groups consisting of SiO4 and BiO6 units.

Monomode optical planar and channel waveguides in Yb3+-doped silicate glasses formed by helium ion implantation

Optical planar and channel waveguides in Yb3+-doped silicate glasses are fabricated by triple-energy helium ion implantation at a total dose of 6.0×1016ions/cm2. The dark mode spectroscopy of the planar waveguide was measured using a prism coupling arrangement. The near-field mode profiles of the planar and channel waveguide were obtained with an end-face coupling system. The refractive index profile was reconstructed by the intensity calculation method. The results indicate that a refractive index enhanced region as well as an optical barrier has been created after the beam process. After post-implantation treatment at 260°C for 1h, the channel waveguides possessed a propagation loss of ∼1.2dB/cm. The acceptable guiding properties suggest that further waveguide lasers may be realized on the He-implanted Yb3+-doped silicate glass waveguides.

Down-conversion in Tm3 +/Yb3 + doped glasses for multicrystalline silicon photo-voltaic module efficiency enhancement

Efficiency enhancement of a multicrystalline silicon solar cell using down-conversion of Tm3+ and Yb3+ doped silicate glasses was investigated. Na2O–CaO–SiO2 glasses doped with Tm3+ or Tm3+ and Yb3+ were prepared. Distributed Bragg Reflector (DBR) coatings were sputtered on the glass surface to control the transmission and reflection of the desired portion of the solar spectrum. These were placed on a multicrystalline silicon solar cell in combination with a solar spectrum simulator. The efficiency of solar cell with Tm3+ or Tm3+ and Yb3+ doped glasses increased compared to as-prepared glass without rare-earth addition. The efficiency of solar cell with rare earth doped glasses was re-measured three times with same samples, and the real efficiency enhancement can be proved. The potentials, limitations and future perspectives of rare-earth doped glasses with DBR structure on the efficiencies of PV modules were discussed.

Controlling the Spectral Characteristics of Bismuth Doped Silicate Glass Based on the Reducing Reaction of Al Powder

Silicate glasses co-doped with Al metal powder and Bi2O3 are prepared. The effects of Al on spectral properties of samples are studied. It is found that the absorption intensity increases with increasing Al concentration in bismuth doped silicate glasses. The near-infrared (NIR) emission of the samples can be controlled by Al powder concentration no matter whether or not excited by 808 nm or 976 nm lasers. Furthermore, the influence of Al on formation of Bi-NIR active ions is discussed. The dependence relationship between the emission property of ∼416 nm and Al concentration is a way to investigate the NIR emission origin of bismuth doped glass.

Improved control of the phosphorous surface concentration during in‐line diffusion of c‐Si solar cells by APCVD

AbstractEmitter formation for industrial crystalline silicon (c‐Si) solar cells is demonstrated by the deposition of phosphorous‐doped silicate glasses (PSG) on p‐type monocrystalline silicon wafers via in‐line atmospheric pressure chemical vapor deposition (APCVD) and subsequent thermal diffusion. Processed wafers with and without the PSG layers have been analysed by SIMS measurements to investigate the depth profiles of the resultant phosphorous emitters. Subsequently, complete solar cells were fabricated using the phosphorous emitters formed by doped silicate glasses to determine the impact of this high‐throughput doping method on cell performance. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

LA-ICP-MS depth profile analysis of apatite: Protocol and implications for (U–Th)/He thermochronometry

Heterogeneous concentrations of α-producing nuclides in apatite have been recognized through a variety of methods. The presence of zonation in apatite complicates both traditional α-ejection corrections and diffusive models, both of which operate under the assumption of homogeneous concentrations. In this work we develop a method for measuring radial concentration profiles of 238U and 232Th in apatite by laser ablation ICP-MS depth profiling. We then focus on one application of this method, removing bias introduced by applying inappropriate α-ejection corrections. Formal treatment of laser ablation ICP-MS depth profile calibration for apatite includes construction and calibration of matrix-matched standards and quantification of rates of elemental fractionation. From this we conclude that matrix-matched standards provide more robust monitors of fractionation rate and concentrations than doped silicate glass standards. We apply laser ablation ICP-MS depth profiling to apatites from three unknown populations and small, intact crystals of Durango fluorapatite. Accurate and reproducible Durango apatite dates suggest that prolonged exposure to laser drilling does not impact cooling ages. Intracrystalline concentrations vary by at least a factor of 2 in the majority of the samples analyzed, but concentration variation only exceeds 5x in 5 grains and 10x in 1 out of the 63 grains analyzed. Modeling of synthetic concentration profiles suggests that for concentration variations of 2x and 10x individual homogeneous versus zonation dependent α-ejection corrections could lead to age bias of >5% and >20%, respectively. However, models based on measured concentration profiles only generated biases exceeding 5% in 13 of the 63 cases modeled. Application of zonation dependent α-ejection corrections did not significantly reduce the age dispersion present in any of the populations studied. This suggests that factors beyond homogeneous α-ejection corrections are the dominant source of overdispersion in apatite (U–Th)/He cooling ages.

Composition dependence of luminescence of Eu and Eu/Tb doped silicate glasses for LED applications

The Eu and Eu/Tb doped silicate glasses are good candidates for light emitting diode (LED) applications. But the optical performance of these glasses is sensitive to variations in chemical composition. In this paper we report our recent findings about the effect of addition of minor components such as B2O3, Al2O3 and CaF2 on the luminescent properties of the above-mentioned glasses. We explore the role of Eu3+ ions as a structural probe of the glasses by determining the asymmetry factor, i.e., the ratio of the emission intensity of the 5D0→7F2 transition to that of the 5D0→7F1 transition. The results show that the asymmetry factor and luminescence lifetimes of as-prepared materials are dependent on composition. White fluorescence is achieved in Eu/Tb co-doped glasses, which can be attributed to the simultaneous generation of red, green and blue wavelengths from Eu3+ and Tb3+ ions. The variation of the excitation wavelength can tune the emission spectra as well as Commission Internationale de L’Eclairage (CIE) chromaticity coordinates of Eu/Tb co-doped glasses for specific applications. The energy transfer from Tb3+ to Eu3+ ions is investigated by analyzing fluorescence spectra and decay curves.

Optical properties of Er3+‐doped glasses for solar‐pumped lasers

AbstractThe quantum efficiency (QE) of Er3+‐doped silicate, tellurite, phosphate and fluoride glasses have been examined under simulated sunlight excitation. The maximum of total QE, the sum of QE of 4S3/2, 4I11/2, 4I13/2→4I15/2 and 4S3/2→4I13/2 transition, is 75% and the maximum of QE1530, the QE of the 4I13/2→4I15/2 transition at 1530 nm, is 34% for 5.47×1019 cm‐3 Er3+‐doped fluoride glass. The figure of merit as laser media στ of silicate glass is 1.00×10‐22 cm2sec, which is the highest in 4 glasses. Although QE1530 of silicate is lower than fluoride, it is possible to compensate the low quantum efficiency to optimize the fiber laser design. Therefore Er3+‐doped fluoride and silicate glasses are expected to be promising candidates as solar‐pumped glass laser (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Investigation of spectroscopic properties, structure and luminescence spectra of Sm3+ doped zinc bismuth silicate glasses

The glasses with compositions 20ZnO·(79.5−x)Bi2O3·xSiO2·0.5Sm2O3 (10⩽x⩽50, mol%) have been synthesized using normal melt-quench technique. Optical absorption and fluorescence spectra of the glasses were recorded at ambient temperature. Judd–Ofelt (J–O) theory has been successfully applied to characterize the absorption and luminescence spectra of these glasses. From the measured intensities of absorption bands of these glasses, the Judd–Ofelt parameters, Ωλ (λ=2, 4, 6) have been evaluated. The variation of Ω2 with Bi2O3 content has been attributed to changes in the asymmetry of the ligand field at the rare earth (RE) ion site (due to structural change) and to changes in RE–O covalency, whereas the variation of Ω6 is found to be strongly dependent on nephlauxetic effect. The shift of the hypersensitive band shows that the covalency of the RE–O decreases with decrease in Bi2O3 content in the host glass. Also, using J–O theory various radiative properties like spontaneous emission probability (Arad), radiative life time (τr), fluorescence branching ratio (βr) and stimulated emission cross-section (σ) for various emission bands of these glasses in the visible spectral region have been determined. A close correlation is observed between the Bi2O3 content and the spectroscopic, radiative and structural properties of the prepared glasses. The values of radiative properties indicated that 4G5/2→6H7/2 and 4G5/2→6H9/2 transitions responsible for orange luminescence might be used in the development of materials for LED’s and other optical devices in the visible region.

Single-frequency gain-switched Ho-doped fiber laser

We demonstrate a single-frequency gain-switched Ho-doped fiber laser based on heavily doped silicate glass fiber fabricated in-house. A Q-switched Tm-doped fiber laser at 1.95 μm was used to gain-switch the Ho-doped fiber laser via in-band pumping. Output power of the single-frequency gain-switched pulses has been amplified in a cladding-pumped Tm-Ho-codoped fiber amplifier with 1.2 m active fiber pumped at 803 nm. Two different nonlinear effects, i.e., modulation instability and stimulated Brillouin scattering, could be seen in the 10 μm-core fiber amplifier when the peak power exceeds 3 kW. The single-frequency gain-switched fiber laser was operated at 2.05 μm, a popular laser wavelength for Doppler lidar application. This is the first demonstration of this kind of fiber laser.

Proton-implanted optical planar waveguides in Yb3+-doped silicate glasses

We report on the characterization of planar waveguides in Yb3+-doped silicate glasses fabricated by double-energy proton implantation at a total dose of 3×1016ions/cm2. The dark mode spectroscopy and near-field mode profile were evaluated by the prism coupling and end-face coupling methods, respectively. The results indicate that a refractive index enhanced region as well as an optical barrier has been created after the beam process. We propose the ion exchange mechanism between the proton and Na+ ions to illustrate the optical barrier and discuss its influence.