Intense up-conversion luminescence from Dy3+-doped multi-component telluroborate glass matrix: Role of CuO nanoparticles embedment

This paper reports an intense up-conversion luminescence from Dy³⁺-doped strontium-telluro-alumino-magnesium-borate glasses for the first time. The samples were made via the melt-quenching method and characterized to determine the influence of various CuO nanoparticles contents change on their up-conversion emission traits. Absorption spectral data were used to calculate the Judd-Ofelt intensity parameters. The sample without CuO nanoparticles revealed two intense photoluminescence up-conversion emission peaks at 478 and 570 nm. In addition, CuO nanoparticles-activated sample displayed about 1.4-fold up-conversion emission intensity improvement due to strong light absorption in the visible to the infrared region at 799 nm excitation. The stimulated emission cross-section of the CuO nanoparticles-activated glasses was increased from 102.4 × 10^-23 to 1301.1 × 10^-23 cm² (nearly 10-fold amplification) while the branching ratio was reduced to 66.9%. Thus, CuO nanoparticles as an additive in the current glass matrix enhanced the up-conversion emission and strengthened the associated nonlinear optical properties. CIE 1931 color matching revealed the influence of CuO in modifying the up-conversion color coordinates, thereby improving the white color purity. The achieved up-conversion emission coupled with the color tunability of the proposed glasses may be advantageous for the up-conversion UV tunable laser making.

Study on particle radiative properties of lignite, hard coal and biomass fly ashes in the infrared wavelength range

Fly ash, which is a by-product of combustion in furnaces or boilers, is used in certain materials as an additive for waste recycling. The optical properties of fly ash and the effects on the heat transfer phenomena of materials used in engineering applications differ and depend on the kind of solid fuel and the combustion conditions. The morphological and the radiative properties of fly ash samples of Turkish lignite, biomass, and hard coal that are burned in different thermal power plants were studied herein. The samples, which were collected from cyclones, were morphologically examined using scanning electron microscopy (SEM) images, and their chemical compositions were analysed by energy dispersive x-ray spectroscopy (EDX). Absorbance measurements were made in the wavelength range from 2.5 to 25 μm, and the discrete dipole approximation (DDA) was applied for a numerical assessment of the radiative properties of the samples. The measured absorbance values of all samples for particle diameters of 25 and 75 μm displayed significant differences in the related wavelength range. The most prominent change was observed in the biomass sample, and the hard coal fly ash had the lowest absorbance values in the related spectrum range. Although the particle shapes of lignite and biomass fly ashes are not same, the changes in the measured absorbance values were similar. The effects of the k index of the complex refractive index (CRI) on the radiative properties were examined for values of 0.01, 0.1, 0.3, 0.5 and 1.0. According to the measured absorption values and the calculated absorption efficiency results, the k index may be between 0.3 and 1.0 at the related wavelength range. It was concluded that the effects of the particle size and absorption index of fly ash on the heat transfer properties are important in the specified wavelength range.

Structural and spectroscopic properties of Er3+ doped sodium lithium borate glasses

The trivalent erbium (Er³⁺⁾ doped sodium lithium borate glass with composition (65-x)B₂O₃-15Na₂O-10PbO-5ZnO-5Li₂O-xEr₂O₃ have been successfully fabricated by melt-quench technique. The structural properties were investigated by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR). The absorption and luminescence spectra of glass samples were measured to determine the spectroscopic properties. The Judd-Ofelt parameters were calculated based on absorption spectra with values of Ω₂, = 4.39, Ω₄ = 3.22, and Ω₆ = 0.91 (×10^-22 cm²) for 2.0 mol% Er³⁺ ion doped sodium lithium borate glass. Furthermore, radiative properties including effective bandwidth (Δλ_eff), radiative transition probability (A_R), radiative lifetime (τ_R), and branching ratio (β_R) were also calculated and analyzed. A strong emission band at 1532 nm was observed corresponding to ⁴I_15/2 → ⁴I_13/2 transition under the excitation wavelength of 528 and 976 nm. The stimulated emission cross-section (σ_e) and figure of merit (FWHM xσ_e) were calculated and compared with other glasses in order to evaluate the properties of the present samples for optical amplifier. Based on the characterization results, we found that the glass with 2.0 mol% Er³⁺ ion doped sodium lithium borate glass had the highest stimulated emission cross section compared to other samples and were comparable with the previous reports.

Silver (Ag) nanoparticles enhanced luminescence properties of Dy3+ ions in borotellurite glasses for white light applications

In the present work, the structural and optical properties of borotellurite glasses co-doped with Dy³⁺ ions and Ag nanoparticles were investigated. From HR-TEM analysis, the average Ag nanoparticle diameter was calculated as 13.7 ± 1 nm. The negative sign of the bonding parameter explored the ionic nature of metal-ligand (DyO) bonds. The emission spectra exhibited three emission bands in blue, yellow and red regions corresponding to ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 and ⁴F_9/2 → ⁶H_11/2 transitions, respectively. The Yellow/Blue (Y/B) ratio of optimal BTD0.5A glass was found to be 1.881 and this low Y/B ratio indicated the fact that Dy³⁺ ions were located in higher symmetrical ligand environment. The CCT values are found to vary from 3717 to 3800 K and hence the present glasses may emit cool white light when excited with UV lamp. The radiative parameters were calculated for all the emission transitions by using JO theory. The decay curves are found to show non-exponential behavior for all the studied glasses. The obtained results were discussed in detail and compared with similar reported glasses.

Spectroscopic studies of Dy3+ ion doped tellurite glasses for solid state lasers and white LEDs

Rare earth ion Dy³⁺-doped tellurite glasses were synthesised in the system of (75-x)TeO₂-15Sb₂O₃-10WO₃-xDy₂O₃ (TSWD glasses). XRD and FTIR characterizations were used to find the crystalline and structural properties. The intensities of the electronic transitions and the ligand environment around the Dy³⁺ ion were determined using the Judd-Ofelt (J-O) theory on the absorption spectra of the glasses. The measured luminescence spectra exhibit intense emissions at 574 and 484nm along with less intense emissions around 662 and 751nm. Various radiative properties of the ⁴F_9/2 excited level of Dy³⁺ ion were calculated for the glasses. Decay profiles were measured to find the life times and quantum efficiencies. Yellow to blue intensity ratio (Y/B), CIE chromaticity coordinates and correlated color temperature (CCT) values are calculated using the emission spectra to evaluate the emitted light. The obtained results suggest the utility of the glasses for potential yellow laser and white LED's applications.

Review of the 9th NLTE code comparison workshop

We review the 9th NLTE code comparison workshop, which was held in the Jussieu campus, Paris, from November 30th to December 4th, 2015. This time, the workshop was mainly focused on a systematic investigation of iron NLTE steady-state kinetics and emissivity, over a broad range of temperature and density. Through these comparisons, topics such as modeling of the dielectronic processes, density effects or the effect of an external radiation field were addressed. The K-shell spectroscopy of iron plasmas was also addressed, notably through the interpretation of tokamak and laser experimental spectra.

Investigations on spectroscopic properties of Er(3+)-doped Li-Zn fluoroborate glass

Er(3+)-doped Li-Zn fluoroborate glass was synthesized via melt quenching technique. Optical properties of the glass were investigated by UV-Vis-NIR absorption and emission spectra. To evaluate the nature of Er(3+)-ligand bond in the glass network, nephelauxetic ratios and bonding parameter were calculated. Judd-Ofelt analysis and hence the radiative properties of the present glass system were evaluated for ascertaining the suitability of the glass for laser applications and compared those with the emission spectra. Absorption cross-sections have been calculated from the absorption spectrum and stimulated emission cross-sections were estimated using McCumber theory for (4)I13/2↔(4)I15/2 transitions. The results of the present glass were compared with those obtained for some other Er(3+)-doped glass systems.

Spectroscopic and energy transfer behavior of Dy(3+) ions in B2O3TeO2PbOPbF2Bi2O3CdO glasses for laser and WLED applications

A new series of white light emitting Dy(3+) doped Lead tellurofluoroborate glasses have been prepared and their spectroscopic and energy transfer behavior were explored through analyzing XRD, FTIR, Raman, SEM, EDAX, optical absorption, photoluminescence and lifetime measurements. The fundamental stretching of the various borate and tellurite networks were identified using FTIR and Raman spectral analysis. The bonding parameter studies reveal the ionic nature of the DyO bond in the present glasses. The Judd-Ofelt (JO) intensity parameters determined from the absorption spectra have been used to investigate the nature of bonding and symmetry orientation of the Dy-ligand field environment. The luminescence intensity increases with increasing Dy(3+) ion concentration up to 0.5wt%, beyond that luminescence quenching is observed. The JO parameters have been used to determine the transition probability (A), stimulated emission cross-section (σP(E)), radiative lifetime (τR) and branching ratios (βR) for the different emission transitions from the (4)F9/2 excited level. The higher σP(E) and βR values of the (4)F9/2→(6)H15/2 and (4)F9/2→(6)H13/2 transitions suggest the possible laser action in the visible region. The Y/B ratio, CIE chromaticity color coordinates (x, y) and Color correlated temperature (CCT) were also estimated from the luminescence spectra for different concentration as well as pumping wavelengths. The x, y chromaticity color coordinates fall within the white light region and the white light can be tuned by varying the excitation wavelengths. The lifetime of the (4)F9/2 excited state were measured and is found to decrease with increasing Dy(3+) ion content. The non-exponential behavior is predominant in higher Dy(3+) ion content glasses and is due to the efficient energy transfer between Dy(3+)Dy(3+) ions. The decay curves were fitted to the Inokuti-Hirayama (IH) model to understand the nature of energy transfer. Among the prepared glasses, 0.5DPTFB glass possesses higher A,βR,σP(E),η values and is suggested for lasers and WLED applications.

Brown haze types due to aerosol pollution at Hefei in the summer and fall

Brown haze episodes were evaluated at Hefei in the summer (June-August) and fall (September-November) seasons, and typical haze types were identified by air-mass back-trajectories and fire spot maps. Compared with clear weather conditions, larger median single scattering albedo values of 0.82 and 0.78 at 550 nm were obtained for the summer and fall haze episodes, respectively. Further, the observed lower scattering Angstrom exponents imply that more large particles than small particles dominated the haze plumes, which is in agreement with the profiles of size distribution. Particles during a haze episode in Hefei grow to a size such that the 0.10 limit for the backscattering ratio is reached, which may indicate that the aged aerosols promote the formation of haze episodes. Three typical haze types were identified: biomass burning, anthropogenic industrial and traffic emissions, and brown carbon. Less negative aerosol radiative forcing efficiencies of -12.7 and -10.9 W m(-2) in summer and fall were estimated, respectively, for haze impacted by biomass burning, which emphasizes an enhanced significance of biomass burning aerosols on climate forcing.

Optical studies of Sm³⁺ ions doped zinc alumino bismuth borate glasses

Zinc Alumino Bismuth Borate (ZnAlBiB) glasses doped with different concentrations of samarium (Sm(3+)) ions were prepared by using melt quenching technique and characterized for their lasing potentialities in visible region by using the techniques such as optical absorption, emission and emission decay measurements. Radiative properties for various fluorescent levels of Sm(3+) ions were estimated from absorption spectral information using Judd-Ofelt (JO) analysis. The emission spectra and con-focal photoluminescence images obtained by 410 nm laser excitation demonstrates very distinct and intense orange-red emission for all the doped glasses. The suitable concentration of Sm(3+) ions in these glasses to act as an efficient lasing material has been discussed by measuring the emission cross-section and branching ratios for the emission transitions. The quantum efficiencies were also been estimated from emission decay measurements recorded for the (4)G5/2 level of Sm(3+) ions. From the measured emission cross-sections, branching ratios, strong photoluminescence features and CIE chromaticity coordinates, it was found that 1 mol% of Sm(3+) ions doped ZnAlBiB glasses are most suitable for the development of visible orange-red lasers.

Optical properties of Nd3+ doped bismuth zinc borate glasses

Glasses with compositions of (100-x) (Bi2ZnOB2O6) -x Nd2O3 (where x=0.1, 0.3, 0.5, 1 and 2 mol%) were prepared by melt quenching method and characterized through optical absorption, emission and decay curve measurements. Optical absorption spectra have been analyzed using Judd-Ofelt theory. The emission spectra exhibit three peaks at 919, 1063 and 1337 nm corresponding to (4)F3/2 to (4)I9/2, (4)I11/2 and (4)I13/2 transitions in the near infrared region. The emission intensity of the (4)F3/2 to (4)I11/2 transition increases with increase of Nd(3+) concentration up to 1 mol% and then concentration quenching is observed for 2 mol% of Nd(3+) concentration. The lifetimes for the (4)F3/2 level are found to decrease with increase in Nd2O3 concentration in the glasses. The decay curves of the glass up to 0.3 mol% of Nd(3+) exhibit single exponential nature and thereafter the curves become nonexponential nature (0.5, 1 and 2 mol%). The nonexponential curve has been fitted to the Inokuti-Hirayama model to understand the nature of energy transfer process.