Search

Borogermanate glasses singly doped with Dy3+ ions were synthesized and then studied using the absorption and luminescence spectra. Spectroscopic changes of Dy3+ ions have been examined for compositional-dependent glasses with various molar ratios GeO2:B2O3. In this work, several spectroscopic parameters of Dy3+ ions were obtained experimentally and compared to the calculated values from the Judd–Ofelt theory. Luminescence spectra measured for borogermanate glasses consist of blue, yellow and red bands, which correspond to 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2 transitions of Dy3+, respectively. Luminescence lifetimes for the 4F9/2 excited state are reduced, whereas the stimulated emission cross-sections for the most intense 4F9/2 → 6H13/2 yellow transition of Dy3+ increase with increasing GeO2 and decreasing B2O3 concentrations in glass-hosts. Quantum efficiency of the 4F9/2 (Dy3+) excited state is nearly independent on molar ratios GeO2:B2O3. Attractive spectroscopic properties related to the 4F9/2 → 6H13/2 transition of Dy3+ ions are found for borogermanate glasses implying their potential utility for yellow laser action and solid-state lighting technology. [ABSTRACT FROM AUTHOR]

Kowalska et al. [[17]] report near-IR luminescence properties of selected rare-Earth ions (Er SP 3+ sp , Pr SP 3+ sp , Ho SP 3+ sp , Tm SP 3+ sp ) in titanate-germanate glasses under excitation of Yb SP 3+ sp . 35683100 17 Kowalska K., Kuwik M., Pisarska J., Pisarski W.A. Near-IR luminescence of rare-earth ions (Er3+, Pr3+, Ho3+, Tm3+) in titanate-germanate glasses under excitation of Yb3+. Rare-Earth ions, as optically active ions, are usually incorporated into the crystalline phases. [Extracted from the article]

Excitation and emission spectra of Pr 3+ :PLZT ceramics have been studied. Several emission bands were measured under blue laser excitation, which correspond to 3 P 0 → 3 H 4 , 1 D 2 → 3 H 4 , 3 P 0 → 3 H 4 and 3 P 0 → 3 F 2 transitions of trivalent Pr 3+ . Their integrated emission intensities were determined. The blue-to-red luminescence intensity ratios of Pr 3+ depend significantly on free sintering/hot pressing methods used for PLZT fabrication and activator concentration. Luminescence decay curves for the 1 D 2 state of Pr 3+ :PLZT ceramics are also presented and discussed. [ABSTRACT FROM AUTHOR]

Lead bismuth gallate glasses doped with Eu 3+ and Dy 3+ ions were examined using excitation and luminescence measurements. From excitation spectrum of Eu 3+ ions the electron–phonon coupling strength and phonon energy of the glass host was calculated. Strong luminescence quenching of Dy 3+ and enhancement of Eu 3+ is well observed, which is due to presence of Bi 3+ → Eu 3+ and Dy 3+ → Bi 3+ energy transfer processes in lead bismuth gallate glass. Luminescence decay analysis and calculations based on Inokuti–Hirayama model confirms this hypothesis. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lead phosphate glasses doped with rare earth ions were prepared. [•] The local structure was examined using X-ray diffraction and spectroscopic methods. [•] Different structural phosphate groups are present in lead phosphate glasses. [•] The electron–phonon coupling strength and phonon energy of the glass host was determined. [•] Several observed emission bands are due to 4f–4f electronic transitions of rare earth ions. [ABSTRACT FROM AUTHOR]

Abstract: Selected heavy metal glasses containing Yb3+ and Er3+ ions have been studied. Near-infrared luminescence spectra at 1.53μm and up-conversion spectra of Er3+ ions were registered under excitation of Yb3+ ions by 975nm diode laser line. The luminescence bands correspond to 4I13/2–4I15/2 (NIR), 4S3/2–4I15/2 (green) and 4F9/2–4I15/2 (red) transitions of Er3+, respectively. The optical transitions of rare earth ions have been examined as a function of glass host. The unusual large spectral linewidth nearly close to 110nm for 4I13/2–4I15/2 transition of Er3+ ions in Yb–Er co-doped lead borate glass was obtained, whereas long-lived NIR luminescence at 1.53μm was detected in lead germanate glass. The NIR luminescence and up-conversion phenomena strongly depend on stretching vibrations of glass host, which was confirmed by FT-IR spectroscopy. [Copyright &y& Elsevier]

This paper deals with broadband near-infrared luminescence properties of lead germanate glass triply doped with Yb3+/Er3+/Tm3+. Samples were excited at 800 nm and 975 nm. Their emission intensities and lifetimes depend significantly on Er3+ and Tm3+ concentrations. For samples excited at 800 nm, broadband emissions corresponding to the overlapped 3H4 → 3F4 (Tm3+) and 4I13/2 → 4I15/2 (Er3+) transitions centered at 1.45 µm and 1.5 µm was identified. Measurements of decay curves confirm reduction of 3H4 (Tm3+), 2F5/2 (Yb3+) and 4I13/2 (Er3+) luminescence lifetimes and the presence of energy-transfer processes. The maximal spectral bandwidth equal to 269 nm for the 3F4 → 3H6 transition of Tm3+ suggests that our glass co-doped with Yb3+/Er3+/Tm3+ is a good candidate for broadband near-infrared emission. The energy transfer from 4I13/2 (Er3+) to 3F4 (Tm3+) and cross-relaxation processes are responsible for the enhancement of broadband luminescence near 1.8 µm attributed to the 3F4 → 3H6 transition of thulium ions in lead germanate glass under excitation of Yb3+ ions at 975 nm. [ABSTRACT FROM AUTHOR]

In this work, spectroscopic properties of europium and erbium ions in heavy metal oxide glasses have been studied. The phonon energy of the glass host was determined based on Eu3+ excitation spectra measurements. Near-IR emission spectra at 1550 nm related to 4I13/2 → 4I15/2 transition of erbium in heavy metal glasses were examined with special regards to luminescence bandwidth and measured lifetime. In particular, correlation between phonon energy and the measured lifetime 4I13/2 (Er3+) was proposed. The luminescence lifetime for the 4I13/2 upper laser state of erbium decreases with increasing phonon energy in glass matrices. Completely different results were obtained glass samples with europium ions, where the 5D0 lifetime increases with increasing phonon energy. Our investigations suggest that the values of measured 5D0 lifetime equal to radiative lifetimes for all heavy metal oxide glasses. [ABSTRACT FROM AUTHOR]

Fluoroindate glasses co-doped with Pr3+/Er3+ ions were synthesized and their near-infrared luminescence properties have been examined under selective excitation wavelengths. For the Pr3+/Er3+ co-doped glass samples several radiative and nonradiative relaxation channels and their mechanisms are proposed under direct excitation of Pr3+ and/or Er3+. The energy transfer processes between Pr3+ and Er3+ ions in fluoroindate glasses were identified. In particular, broadband near-infrared luminescence (FWHM = 278 nm) associated to the 1G4 → 3H5 (Pr3+), 1D2 → 1G4 (Pr3+) and 4I13/2 → 4I15/2 (Er3+) transitions of rare earth ions in fluoroindate glass is successfully observed under direct excitation at 483 nm. Near-infrared luminescence spectra and their decays for glass samples co-doped with Pr3+/Er3+ are compared to the experimental results obtained for fluoroindate glasses singly doped with rare earth ions. [ABSTRACT FROM AUTHOR]

Lead tungstate PbWO4 nanocrystals in transparent lead borate glass-ceramics containing Er3+ ions were fabricated. Luminescence spectra at about 1530 nm due to main 4 I13/2-4 I15/2 laser transition of Er3+ ions were examined for glass samples before and after heat treatment. Near-infrared luminescence of Er3+ ions in glass-ceramics is enhanced and long-lived in comparison to precursor glasses. It suggests that the Er3+ ions are partially incorporated into PbWO4 crystalline phase. [ABSTRACT FROM AUTHOR]

Novel multicomponent titanate-germanate glasses singly doped with transition metal (Cr3+) and rare earth ions (Eu3+) were synthesized and the glass transition temperatures and thermal stability parameters were determined using DSC measurements. X-ray diffraction analysis confirmed fully amorphous nature of the received samples. Their structural and optical properties were compared with germanate glasses without TiO2. Correlation between local structure and optical properties in titanate-germanate glasses is well evidenced by FT-IR, Raman, EPR, and luminescence spectroscopy. In particular, luminescence spectra and their decays are examined for glass samples, where GeO2 was partially substituted by TiO2. [ABSTRACT FROM AUTHOR]

In this paper, we report on fabricating optical fibers with a controlled process of crystallization core during the drawing process. The research and synthesis of the core material of silica-germanium-antimony oxide glass were discussed. We also investigated the optical and luminescence properties were in relation to concentrating Eu 2 O 3 and P 2 O 5. Based on this investigation, we selected the most promising material for optical fiber core. In the next step, we drew optical fibers using a well-known rod-in-tube method. After drawing, we examine the optical fibers for luminescence shape changes. We observed a promising similarity between optical fibers and heat-treated samples with confirmed nanocrystals. Finally, XRD and TEM measurements confirm EuPO 4 nanocrystals at the core of the optical fiber. Highlighting the successful control of crystallization in the one-step method used to draw optical fibers. [ABSTRACT FROM AUTHOR]

Transparent Yb3+/Er3+ glass-ceramic was successfully obtained by the extrusion method. The extrusion of oxyfluoride tellurite-germanate glass co-doped with Yb3+ and Er3+ ions at 520 ℃ resulted in the formation of Ba0.75Er0.25F2.25 nanocrystals, leading to an increase in the upconversion (UC) emission intensity of 35 times in glass-ceramic with respect to the glass. The glass to glass-ceramic transition was confirmed by X-ray diffraction (XRD) and Transmission electron microscope (TEM). Also, the structural changes that occurred during crystallization were assessed using Fourier-transform infrared (FTIR) spectroscopy. Furthermore, the pump power and temperature UC emission dependence of glass and glass-ceramic under 976 nm laser excitation were investigated in detail. The assessments showed that i) two-phonons are involved in the UC process and ii) the temperature has a significant influence over it. The Yb3+/Er3+ codoped glass-ceramic shows relatively high Sa and Sr values in a wide temperature range from 300 to 573 K, presenting the maximal Sa value of 3.50 × 10-3 at 573 K and the maximal Sr value of 6.30 × 10-3 at 364 K. These results suggest that the glass-ceramic is a good candidate for optical applications such as luminescent thermometry. [ABSTRACT FROM AUTHOR]

In this study, a comprehensive analysis of emission in erbium-doped and erbium and ytterbium co-doped fluoroindate glasses has been presented. The luminescence of the erbium transitions and the effect of ytterbium co-doping under 488, 808 and 976 nm laser excitation have been discussed. Optimization of rare-earth (RE) ions doping concentration and the energy transfer processes related to the sensibilization effect in Er3+/Yb3+ co-doped fluoroindate glasses focusing on the reciprocal distribution of radiative transitions, energy transfer parameters, and lifetimes have been analyzed. The luminescence consists of several bands in the visible (525, 546 and 660 nm) and the infrared (1550 and 2700 nm) spectral regions that correspond to characteristic radiative energy transitions within the erbium ions. In glasses co-doped with the Er3+/Yb3+ system, an augmentation in the emission intensity was observed in the visible and at 1550 nm, while a decrease was observed in the 2700 nm infrared band. The increase of the Yb3+: 2F 5/2 lifetime under 488, 808 and 976 nm excitation showed significant Er3+: 4I 11/2 → Yb3+: 2F 5/2 back energy transfer. Based on the analysis of the available literature, it can be concluded that energy transfer upconversion and cooperative energy upconversion play a significant role in modulating luminescence intensity values within the examined emission bands. This effect is likely enhanced due to the incorporation in a low phonon energy glass matrix. As a result of the above optimization, a glass optical fiber co-doped with 0.8 YbF 3 /1.4 ErF 3 (in mol%) was drawn and characterized, showing a strong emission at 2.77 μm. The optimized Er3+/Yb3+ co-doped fluoroindate glass and glass optical fiber confirmed their ability to be used in the visible and near-infrared spectral regions as efficient optical fiber sources. [ABSTRACT FROM AUTHOR]

In this work, Tm3+ doped and Tm3+/Ho3+ co-doped germanate glasses with various TiO 2 concentrations have been examined using optical spectroscopy. The broad emission bands corresponding to 3F 4 →3H 6 (1.8 μm) and 5I 7 →5I 8 (2 μm) transitions of thulium and holmium ions were registered, respectively. It was observed that the intensity of near-infrared emission bands significantly changes with increasing titanium oxide content in the glass composition. Furthermore, the energy transfer process from Tm3+ to Ho3+ ions in studied glass systems was confirmed and discussed. The dependence of spectroscopic parameters like full width at half maximum (FWHM) and energy transfer efficiency (η ET) on increased TiO 2 concentration in glass host was established. [ABSTRACT FROM AUTHOR]

In this contribution a comprehensive spectroscopic study of Dy3+ doped fluoroindate glass samples and glass fiber is presented. The mid-infrared (MIR) emission from DyF 3 doped bulk glass samples (0.2, 0.4, 0.8, 1.2, 1.4, 1.6 mol.%) is investigated when pumping at 1320 nm. A broadband mid-infrared emission spanning from 2800 nm to 3500 nm with 0.88 ms emission lifetime of the 6H 13/2 level in 0.2 mol.% glass sample was observed. Also 0.2 mol.% of DyF 3 doped fluoroindate glass fiber was drawn and its photoluminescence properties were studied showing the emission spectrum to 3500 nm and the 6H 13/2 level lifetime of 0.91 ms. The results obtained show that fluoroindate glass is a good candidate for further development of tunable fiber lasers and broadband mid-infrared spontaneous emission fiber sources. [ABSTRACT FROM AUTHOR]

This work presents an analysis of the spectroscopic properties of glass and glass ceramics co-doped with Ni2+ and Er3+ ions. Spectroscopic analysis showed the embedding of nickel ions in the gamma-gallium oxide nanocrystals as a result of heat treatment of the glass samples. Analysis of the luminescence properties of the obtained samples under 940 nm and 980 nm pump excitation allowed the selection of a proper Er3+ ions concentration for further optical fiber fabrication. Measured lifetime results of glass-ceramics samples confirm energy transfer from nickel ions to erbium. In the process of drawing the optical fiber, it was possible to create a transparent nanocrystalline glass-ceramic core, as confirmed by XRD results. The produced glass-ceramic optical fiber was characterized by broadband emission in the range from 1100 nm to 1650 nm corresponding to the 3T 2 (3F) →3A 2 (3F) (Ni2+) and 4I 13/2 → 4I 15/2 (Er3+) transitions for 940 nm and 980 nm pump excitation. The Er3+ to Ni2+ ions emission intensity ratio of the fabricated glass-ceramic fiber was estimated to be 0.84 and 7.14 for 940 nm and 980 nm optical pumps, respectively. [ABSTRACT FROM AUTHOR]

In this work, the series of silicate xerogels co-doped with Gd3+ and Eu3+ ions have been synthesized via a sol-gel method and further processed into nano-glass-ceramic materials. The mutual molar ratio of trivalent metal ions' acetates in samples' compositions was gradually modified as follows: La3+:Gd3+:Eu3+ = (0.95-x):x:0.05, x = 0.05, 0.25, 0.45, 0.65, and 0.90; hence the molar ratio of Gd3+:Eu3+ (R Gd/Eu) was set from 1 through 5, 9, 13 up to 18. XRD measurements confirmed the amorphous nature of fabricated xerogels, but their heat-treatment successfully triggered the crystallization of hexagonal LaF 3 fraction with an average size of about ∼10 nm, which was additionally confirmed by HR-TEM microscopy. Additionally, it was found that the LaF 3 phase crystallized in a whole range of proposed La(CH 3 COO) 3 :Gd(CH 3 COO) 3 molar ratio, and Gd3+ ions played only the role of dopant and replaced La3+ cation in the fluoride crystal lattice. The optical characterization of prepared sol-gel samples involved the registration of absorption, excitation and emission spectra, along with the luminescence decay analysis from the 6P 7/2 (Gd3+) and the 5D 0 (Eu3+) excited states. For nano-glass-ceramics defined by R Gd/Eu = 13 and 18, the unexpected prolongation of the τ(6P 7/2):Gd3+ lifetimes was denoted, compared with samples singly-doped with Gd3+. The changes in photoluminescence behavior of studied samples are strongly dependent on the nature of the fabricated sol-gel samples, the established molar ratios of La3+:Gd3+:Eu3+, and the tendency of cation-exchange in LaF 3 nanocrystal lattice by Gd3+ and Eu3+ ions. [ABSTRACT FROM AUTHOR]

LMA (Large Mode Area) optical fibers are presently under active investigation to explore their potential for generating laser action or broadband emission directly within the optical fiber structure. Additionally, a wide mode profile significantly reduces the power distribution density in the fiber cross-section, minimizing the power density, photodegradation, or thermal damage. Multi-stage deposition in the MCVD-CDT system was used to obtain the structural doping profile of the LMA fiber multi-ring core doped with Tm3+ and Tm3+/Ho3+ layer profiles. The low alumina content (Al2O3: 0.03wt%) results in low refractive index modification. The maximum concentrations of the lanthanide oxides were Tm2O3: 0.18wt % and Ho2O3: 0.15wt%. The double-clad construction of optical fiber with emission spectra in the eye-safe spectral range of (1.55–2.10 µm). The calculated LP01 Mode Field Diameter (MFD) was 69.7 µm (@ 2000 nm, and 1/e of maximum intensity), which confirms LMA fundamental mode guiding conditions. The FWHM and λmax vs. fiber length are presented and analyzed as a luminescence profile modification. The proposed structured optical fiber with a ring core can be used in new broadband optical radiation source designs. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) luminescence of Pr3+ and Tm3+ ions in titanate‐germanate glasses has been studied for laser and fiber amplifier applications. The effect of the molar ratio GeO2:TiO2 (from 5:1 to 1:5) on spectroscopic properties of glass systems was studied by absorption, luminescence measurements, and theoretical calculations using the Judd–Ofelt theory. It was found that independent of the TiO2 concentration, intense NIR emissions at 1.5 and 1.8 μm were observed for glasses doped with Pr3+ and Tm3+ ions, respectively. Moreover, several spectroscopic and NIR laser parameters for Pr3+ and Tm3+ ions, such as emission bandwidth, stimulated emission cross‐section, quantum efficiency, gain bandwidth, and figure of merit, were determined. The results were discussed in detail and compared to the different laser glasses. Systematic investigations indicate that Pr3+‐doped system with GeO2:TiO2 = 2:1 and Tm3+‐doped glass with GeO2:TiO2 = 1:2 present profit laser parameters and could be successfully applied to NIR lasers and broadband optical amplifiers. [ABSTRACT FROM AUTHOR]

Double-clad optical fiber with a multi-ring core profile doped with thulium and holmium fabricated by Modified Chemical Vapor Deposition Chelate Doping Technology (MCVD-CDT) is presented. The measured Tm2O3 and Ho2O3 complexes' weight concentrations were 0.5% and 0.2% respectively. Numerical analyses show weakly guiding conditions and 42.2 µm of MFD LP01 at 2000 nm. The low NA numerical aperture (NA = 0.054) was obtained for the 20/250 µm core/cladding ratio optical fiber construction. The emission spectra in the range of 1.6–2.1 µm vs. the fiber length are presented. The full width at half maximum (FWHM) decreases from 318 to 270 nm for fiber lengths from 2 to 10 m. The presented fiber design is of interest for the development of new construction of optical fibers operating in the eye-safe spectral range. [ABSTRACT FROM AUTHOR]

Double-clad optical fiber with a multi-ring core profile doped with thulium and holmium fabricated by Modified Chemical Vapor Deposition Chelate Doping Technology (MCVD-CDT) is presented. The measured Tm2O3 and Ho2O3 complexes' weight concentrations were 0.5% and 0.2% respectively. Numerical analyses show weakly guiding conditions and 42.2 µm of MFD LP01 at 2000 nm. The low NA numerical aperture (NA = 0.054) was obtained for the 20/250 µm core/cladding ratio optical fiber construction. The emission spectra in the range of 1.6–2.1 µm vs. the fiber length are presented. The full width at half maximum (FWHM) decreases from 318 to 270 nm for fiber lengths from 2 to 10 m. The presented fiber design is of interest for the development of new construction of optical fibers operating in the eye-safe spectral range. [ABSTRACT FROM AUTHOR]

The near-infrared luminescence properties of Pr3+/Yb3+: PLZT ferroelectric ceramics have been examined for the first time. Independently, upon either 450 nm (Pr3+) or 980 nm (Yb3+) excitation, luminescence centered at 1340 nm was observed, which corresponds to the 1G4→3H5 transition of Pr3+. Several spectroscopic parameters for the 1G4→3H5 transition of Pr3+ ions were determined. The average product of emission cross section and radiative lifetime were relatively large for all x/65/35 PLZT samples ( x=6-10) studied, with values close to 105±2 (×10−26 cm2·s). These spectroscopic investigations indicate that Pr3+/Yb3+: PLZT ferroelectric ceramics are promising candidate for efficient sources emitting near-infrared radiation at 1340 nm. [ABSTRACT FROM AUTHOR]

An investigation of fluoroindate glass and fiber co-doped with Yb3+/Er3+ ions as a potential temperature sensor was assessed using the fluorescence intensity ratio (FIR) technique. Analysis of thermally coupled levels (TCLs—2H11/2 and 4S3/2), non-thermally coupled levels (non-TCLs—4F7/2 and 4F9/2), and their combination were examined. Additionally, the luminescent stability of the samples under constant NIR excitation using different density power at three different temperatures was carried out. The obtained values of absolute sensitivity (0.003 K−1—glass, 0.0019 K−1—glass fiber 2H11/2 → 4S3/2 transition) and relative sensitivity (2.05% K−1—glass, 1.64% K−1—glass fiber 4F7/2 → 4F9/2 transition), as well as high repeatability of the signal, indicate that this material could be used in temperature sensing applications. [ABSTRACT FROM AUTHOR]

Nanophosphors are widely used, especially in biological applications in the first and second biological windows. Currently, nanophosphors doped with lanthanide ions (Ln3+) are attracting much attention. However, doping the matrix with lanthanide ions is associated with a narrow luminescence bandwidth. This paper describes the structural and luminescence properties of co-doped LaPO4 nanophosphors, fabricated by the co-precipitation method. X-ray structural analysis, scanning electron microscope measurements with EDS analysis, and luminescence measurements (excitation 395 nm) of LaPO4:Eu3+/Nd3+ and LaPO4:Eu3+/Nd3+/Yb3+ nanophosphors were made and energy transfer between rare-earth ions was investigated. Tests performed confirmed the crystal structure of the produced phosphors and deposition of rare-earth ions in the structure of LaPO4 nanocrystals. In the range of the first biological window (650–950 nm), strong luminescence bands at the wavelengths of 687 nm and 698 nm (5D0 → 7F4:Eu3+) and 867 nm, 873 nm, 889 nm, 896 nm, and 907 nm (4F3/2 → 4I9/2:Nd3+) were observed. At 980 nm, 991 nm, 1033 nm (2F5/2 → 2F7/2:Yb3+) and 1048 nm, 1060 nm, 1073 nm, and 1080 nm (4F3/2 → 4I9/2:Nd3+), strong bands of luminescence were visible in the 950 nm–1100 nm range, demonstrating that energy transfer took place. [ABSTRACT FROM AUTHOR]

Modified barium gallo-germanate glass hosts are still worthy of attention in studying structure–property relationships. In this work, two different series of glass systems based on (60-x)GeO2-xTiO2-30BaO-10Ga2O3 and (60-x)GeO2-xB2O3-30BaO-10Ga2O3 (x = 10, 30, 50 mol%) were synthesized, and their properties were studied using spectroscopic techniques. X-ray diffraction (XRD) patterns revealed that all fabricated glasses were fully amorphous material. The absorption edge shifted toward the longer wavelengths with a gradual substitution of GeO2. The spectroscopic assignments of titanium ions were performed with excitation and emission spectra compared to the additional sample containing an extremely low content of TiO2 (0.005 mol%). On the basis of Raman and FT-IR investigations, it was found that increasing the TiO2 content caused a destructive effect on the GeO4 and GeO6 structural units. The Raman spectra of a sample containing a predominantly TiO2 (50 mol%) proved that the band was located near 650 cm−1, which corresponded to the stretching vibration of Ti-O in TiO6 unit. The deconvoluted IR results showed that the germanate glass network consisted of the coexistence of two BO3 and BO4 structural groups. Based on the experimental investigations, we concluded that the developed materials are a promising candidate for use as novel glass host matrices for doping rare-earth and/or transition metal ions. [ABSTRACT FROM AUTHOR]

In this paper, the effect of the GeO2:TiO2 molar ratio in glass composition on the spectroscopic properties of germanate glasses was systematically investigated. The visible luminescence bands associated with characteristic 1D2 → 3H4 (red), 5S2, 5F4 → 5I8 (green), and 1D2 → 3F4 (blue) transitions of Pr3+, Ho3+, and Tm3+ ions in systems modified by TiO2 were well observed, respectively. It was found that the luminescence intensity of glasses containing Pr3+ and Ho3+ ions increases, whereas, for Tm3+-doped systems, luminescence quenching with increasing content of TiO2 was observed. Based on Commission Internationale de I'Eclairage (CIE) chromaticity coordinates (x, y) analysis, it was demonstrated that the value of chromaticity coordinates for all glasses depends on the GeO2:TiO2 molar ratio. The addition of TiO2 to system compositions doped with Tm3+ ions shifts the (x, y) to the center of the CIE diagram. However, chromaticity coordinates evaluated for glasses containing Pr3+ ions move to a purer red color. Our results confirm that the spectroscopic properties of the studied glasses strongly depend on TiO2 content. Moreover, it can be stated that germanate-based glass systems modified by TiO2 can be used for optoelectronics in RGB technology as red (Pr3+), green (Ho3+), and blue (Tm3+) emitters. [ABSTRACT FROM AUTHOR]

In this work, the series of Dy3+-doped silicate xerogels were synthesized by sol-gel technique and further processed at 350 °C into SiO2-LaF3:Dy3+ nano-glass-ceramic materials. The X-ray diffraction (XRD) measurements, along with the thermal analysis, indicated that heat-treatment triggered the decomposition of La(TFA)3 inside amorphous sol-gel hosts, resulting in the formation of hexagonal LaF3 phase with average crystal size at about ~10 nm. Based on the photoluminescence results, it was proven that the intensities of blue (4F9/2 → 6H15/2), yellow (4F9/2 → 6H13/2), and red (4F9/2 → 6H11/2) emissions, as well as the calculated yellow-to-blue (Y/B) ratios, are dependent on the nature of fabricated materials, and from fixed La3+:Dy3+ molar ratios. For xerogels, the emission was gradually increased, and the τ(4F9/2) lifetimes were elongated to 42.7 ± 0.3 μs (La3+:Dy3+ = 0.82:0.18), however, for the sample with the lowest La3+:Dy3+ molar ratio (0.70:0.30), the concentration quenching was observed. For SiO2-LaF3:Dy3+ nano-glass-ceramics, the concentration quenching effect was more visible than for xerogels and started from the sample with the highest La3+:Dy3+ molar ratio (0.988:0.012), thus the τ(4F9/2) lifetimes became shorter from 1731.5 ± 5.7 up to 119.8 ± 0.4 μs. The optical results suggest, along with an interpretation of XRD data, that Dy3+ ions were partially entered inside LaF3 phase, resulting in the shortening of Dy3+-Dy3+ inter-ionic distances. [ABSTRACT FROM AUTHOR]

In this work, the synthesis and characterization of Li2MgGeO4:Ho3+ ceramics were reported. The X-ray diffraction measurements revealed that the studied ceramics belong to the monoclinic Li2MgGeO4. Luminescence properties were analyzed in the visible spectral range. Green and red emission bands correspondent to the 5F4,5S2→5I8 and 5F5→5I8 transitions of Ho3+ were observed, and their intensities were significantly dependent on activator concentration. Luminescence spectra were also measured under direct excitation of holmium ions or ceramic matrix. Holmium ions were inserted in crystal lattice Li2MgGeO4, giving broad blue emission and characteristic 4f-4f luminescent transitions of rare earths under the selective excitation of the ceramic matrix. The presence of the energy transfer process between the host lattice and Ho3+ ions was suggested. [ABSTRACT FROM AUTHOR]

The effect of BaF2, MgF2, and AlF3 on the structural and luminescent properties of gallo-germanate glass (BGG) doped with erbium ions was investigated. A detailed analysis of infrared and Raman spectra shows that the local environment of erbium ions in the glass was influenced mainly by [GeO]4 and [GeO]6 units. Moreover, the highest number of non-bridging oxygens was found in the network of the BGG glass modified by MgF2. The 27Al MAS NMR spectrum of BGG glass with AlF3 suggests the presence of aluminum in tetra-, penta-, and octahedral coordination geometry. Therefore, the probability of the 4I13/2→4I15/2 transition of Er3+ ions increases in the BGG + MgF2 glass system. On the other hand, the luminescence spectra showed that the fluoride modifiers lead to an enhancement in the emission of each analyzed transition when different excitation sources are employed (808 nm and 980 nm). The analysis of energy transfer mechanisms shows that the fluoride compounds promote the emission intensity in different channels. These results represent a strong base for designing glasses with unique luminescent properties. [ABSTRACT FROM AUTHOR]

Glass-ceramic is semi-novel material with many applications, but it is still problematic in obtaining fibers. This paper aims to develop a new glass-ceramic material that is a compromise between crystallization, thermal stability, and optical properties required for optical fiber technology. This compromise is made possible by an alternative method with a controlled crystallization process and a suitable choice of the chemical composition of the core material. In this way, the annealing process is eliminated, and the core material adopts a glass-ceramic character with high transparency directly in the drawing process. In the experiment, low phonon antimony-germanate-silicate glass (SGS) doped with Eu3+ ions and different concentrations of P2O5 were fabricated. The glass material crystallized during the cooling process under conditions similar to the drawing processes'. Thermal stability (DSC), X-ray photo analysis (XRD), and spectroscopic were measured. Eu3+ ions were used as spectral probes to determine the effect of P2O5 on the asymmetry ratio for the selected transitions (5D0 → 7F1 and 5D0 → 7F2). From the measurements, it was observed that the material produced exhibited amorphous or glass-ceramic properties, strongly dependent on the nucleator concentration. In addition, the conducted study confirmed that europium ions co-form the EuPO4 structure during the cooling process from 730 °C to room temperature. Moreover, the asymmetry ratio was changed from over 4 to under 1. The result obtained confirms that the developed material has properties typical of transparent glass-ceramic while maintaining high thermal stability, which will enable the fabrication of fibers with the glass-ceramic core. [ABSTRACT FROM AUTHOR]

Inorganic glasses co-doped with rare-earth ions have a key potential application value in the field of optical communications. In this paper, we have fabricated and then characterized multicomponent TiO2-modified germanate glasses co-doped with Yb3+/Ln3+ (Ln = Pr, Er, Tm, Ho) with excellent spectroscopic properties. Glass systems were directly excited at 980 nm (the 2F7/2 → 2F5/2 transition of Yb3+). We demonstrated that the introduction of TiO2 is a promising option to significantly enhance the main near-infrared luminescence bands located at the optical telecommunication window at 1.3 μm (Pr3+: 1G4 → 3H5), 1.5 μm (Er3+: 4I13/2 → 4I15/2), 1.8 μm (Tm3+: 3F4 → 3H6) and 2.0 μm (Ho3+: 5I7 → 7I8). Based on the lifetime values, the energy transfer efficiencies (ηET) were estimated. The values of ηET are changed from 31% for Yb3+/Ho3+ glass to nearly 53% for Yb3+/Pr3+ glass. The investigations show that obtained titanate–germanate glass is an interesting type of special glasses integrating luminescence properties and spectroscopic parameters, which may be a promising candidate for application in laser sources emitting radiation and broadband tunable amplifiers operating in the near-infrared range. [ABSTRACT FROM AUTHOR]

The results presented in this communication concern visible and near-IR emission of Pr3+ ions in selected inorganic glasses, i.e., borate-based glass with Ga2O3 and BaO, lead-phosphate glass with Ga2O3, gallo-germanate glass modified by BaO/BaF2, and multicomponent fluoride glass based on InF3. Glasses present several emission bands at blue, reddish orange, and near-infrared spectral ranges, which correspond to 4f–4f electronic transitions of Pr3+. The profiles of emission bands and their relative intensity ratios depend strongly on glass-host. Visible emission of Pr3+ ions is tuned from red/orange for borate-based glass to nearly white light for multicomponent fluoride glass based on InF3. The positions and spectral linewidths for near-infrared luminescence bands at the optical telecommunication window corresponding to the 1G4 → 3H5, 1D2 → 1G4, and 3H4 → 3F3,3F4 transitions of Pr3+ are dependent on glass-host matrices and excitation wavelengths. Low-phonon fluoride glasses based on InF3 and gallo-germanate glasses with BaO/BaF2 are excellent candidates for broadband near-infrared optical amplifiers. Spectroscopic properties of Pr3+-doped glasses are compared and discussed in relation to potential optical applications. [ABSTRACT FROM AUTHOR]

Lead phosphate glasses singly-doped with selected Ln3+ ions (Ln = Pr, Tm) were prepared by traditional melt-quenching method. The effect of concentration of optical active dopants in glass composition on spectroscopic properties of lead phosphate glasses were systematically investigated based on excitation, visible and near-infrared emission spectra as well as luminescence decay analysis. It was found that the luminescence intensity decreases with increasing content of Pr3+ and Tm3+ ions due to the concentration quenching. Also, the luminescence lifetimes of 1D 2 , 1G 4 (Pr3+) and 1D 2 , 3H 4 (Tm3+) states decrease with increasing concentration of both ions. Based on luminescence decay analysis and calculations using theoretical Inokuti-Hirayama model it was confirmed that non-radiative processes like cross-relaxation among the donor systems are dominate and influence direct donor-acceptor energy transfer in lead phosphate glasses. Moreover, the obtained results suggest clearly lower self-quenching emission in lead phosphate glasses doped with Pr3+ than Tm3+ ions. • Lead phosphate glasses singly doped with Pr3+ and Tm3+ were obtained. • Luminescence spectra of Ln3+ (Ln = Pr and Tm) and their decays were examined. • The quenching of the visible and near-infrared luminescence were observed when concentration of Pr3+ and Tm3+ ions increase. • The luminescence lifetimes decrease with increasing concentration of Ln3+ ions. • The luminescence quenching via non-radiative energy transfer processes was explained by theoretical Inokuti-Hirayama model. [ABSTRACT FROM AUTHOR]

In this paper, some series of lead borate glasses and glass ceramics singly doped with Dy3+ ions were prepared and then studied using spectroscopic techniques. Our research includes mainly studies of the luminescence properties of received materials for white light. The luminescence bands associated with the characteristic 4F9/2→6H15/2 (blue), 4F9/2→6H13/2 (yellow) and 4F9/2→6H11/2 (red) transitions of trivalent dysprosium in lead borate systems are well observed. In particular, the Commission Internationale de I'Eclairage (CIE) chromaticity coordinates (x, y) were calculated in relation to potential applications for white light-emitting diodes (W-LEDs). Their values depend on the relative B2O3/PbO ratios and PbX2 contents (where X = Cl, F, Br) in glass composition. For glass-ceramics, the chromaticity coordinates are changed significantly under different excitation wavelengths. [ABSTRACT FROM AUTHOR]

The effect of oxide modifiers on multiple properties (structural and spectroscopic) of phosphate glasses with molar composition 60P2O5-(10−x)Ga2O3-30MO-xEu2O3 and 60P2O5-(10−y)Ga2O3-30MO-yEr2O3 (where M = Ca, Sr, Ba; x = 0, 0.5; y = 0, 1) were systematically examined and discussed. The local structure of systems was evidenced by the infrared (IR-ATR) and Raman spectroscopic techniques. The spectroscopic behaviors of the studied glass systems were determined based on analysis of recorded spectra (excitation and emission) as well as luminescence decay curves. Intense red and near-infrared emissions (1.5 μm) were observed for samples doped with Eu3+ and Er3+ ions, respectively. It was found that the value of fluorescence intensity ratio R/O related to 5D0→7F2 (red) and 5D0→7F1 (orange) transition of Eu3+ ions depends on the oxide modifiers MO in the glass host. However, no clear influence of glass modifiers on the luminescence linewidth (FWHM) was observed for phosphate systems doped with Er3+ ions. Moreover, the 5D0 and 4I13/2 luminescence lifetimes of Eu3+ and Er3+ ions increase with the increasing ionic radius of M2+ (M = Ca, Sr, Ba) in the host matrix. The obtained results suggest the applicability of the phosphate glasses with oxide modifiers as potential red and near-infrared photoluminescent materials in photonic devices. [ABSTRACT FROM AUTHOR]

This work reports on the analysis of structural and spectroscopic properties of the fluoroindate glasses co-doped with Er3+/Ho3+. Structural analysis showed that erbium and holmium ions were modifier ions and depolymerizedof the fluoroindate glass network. The energy transfer processes between rare - earth ions in fluoroindate glasses pumped by and 980 nm laser diode have been also examined. Due to partial Er3+ → Ho3+ energy transfer and superposition of Er3+: 4I 11/2 → 4I 13/2 (2.77 μm)+ Ho3+: 5I 6 → 5I 7 (2.85 μm) radiative transitions in fluoroindate glass co-doped with 0.8ErF 3 /1.6HoF 3 , a broadening 3 μm luminescence (Δλ= 201 nm) was obtained. The overall energy transfer efficiency η ET1 + η ET2 was calculated to be 95% indicating efficient sensitization of the holmium ions by erbium. [ABSTRACT FROM AUTHOR]

In the present work, the Tb3+/Eu3+ co-activated sol-gel glass-ceramic materials (GCs) containing MF3 (M = Y, La) nanocrystals were fabricated during controlled heat-treatment of silicate xerogels at 350 °C. The studies of Tb3+ → Eu3+ energy transfer process (ET) were performed by excitation and emission spectra along with luminescence decay analysis. The co-activated xerogels and GCs exhibit multicolor emission originated from 4fn–4fn optical transitions of Tb3+ (5D4 → 7FJ, J = 6–3) as well as Eu3+ ions (5D0 → 7FJ, J = 0–4). Based on recorded decay curves, it was found that there is a significant prolongation in luminescence lifetimes of the 5D4 (Tb3+) and the 5D0 (Eu3+) levels after the controlled heat-treatment of xerogels. Moreover, for both types of prepared GCs, an increase in ET efficiency was also observed (from ηET ≈ 16% for xerogels up to ηET = 37.3% for SiO2-YF3 GCs and ηET = 60.8% for SiO2-LaF3 GCs). The changes in photoluminescence behavior of rare-earth (RE3+) dopants clearly evidenced their partial segregation inside low-phonon energy fluoride environment. The obtained results suggest that prepared SiO2-MF3:Tb3+, Eu3+ GC materials could be considered for use as optical elements in RGB-lighting optoelectronic devices operating under near-ultraviolet (NUV) excitation. [ABSTRACT FROM AUTHOR]

The influence of Cr3+ concentration on near-infrared emission of Ho3+ in barium gallo-germanate glass has been studied. Near-infrared emission bands, due to 4T 2 → 4A 2 (Cr3+) as well as 5I 6 → 5I 8 and 5I 7 → 5I 8 (Ho3+) transitions, were observed under excitation of Cr3+. The enhanced and broadband near-infrared emission was obtained for glasses in the presence of transition metal (Cr3+) and rare earth (Ho3+) ions. This prosperity was optimized as a function of donor (Cr3+) and acceptor (Ho3+) concentration. The integrated intensities of emission bands were determined and their values are found to be maximal at 0.25 mol% Cr3+ and 0.5 mol% Ho3+. The energy transfer from Cr3+ to Ho3+ occurs through a nonradiative process with an efficiency up to 23%. • Cr3+/Ho3+ co-doped barium gallo-germanate glasses were studied for NIR emission. • NIR emission spectra of Ho3+ ions in glasses were measured under excitation of Cr3+. • Emission bands are due to 4T 2.→ 4A 2 (Cr3+), 5I 6 → 5I 8 and 5I 7 → 5I 8 (Ho3+) transitions • The relative emission band intensities of Ho3+ depend critically on Cr3+ concentration. • The energy transfer from Cr3+ to Ho3+ with an efficiency up to 23% occurs. [ABSTRACT FROM AUTHOR]

Abstract: In this work, silica powders and transparent glass‐ceramic materials containing LaF3:Eu3+ nanocrystals were synthesized using the low‐temperature sol‐gel technique. Prepared samples were characterized by TG/DSC analysis as well as X‐ray diffraction and IR spectroscopy. The transformation from liquid sols toward bulk powders and xerogels was also examined and analyzed. The optical behavior of prepared Eu3+‐doped sol‐gel samples were evaluated based on photoluminescence excitation (PLE: λem = 611 nm) and emission (PL: λexc = 393 nm, λexc = 397 nm) spectra as well as luminescence decay analysis. The series of luminescence lines located within reddish‐orange spectral scope were registered and identified as the intra‐configurational 4f6‐4f6 transitions originated from Eu3+ optically active ions (5D0 → 7FJ, J = 0‐4). Moreover, the R/O‐ratio was also calculated to estimate the symmetry in local framework around Eu3+ ions. The luminescence spectra and double‐exponential character of decay curves recorded for fabricated nanocrystalline sol‐gel samples (τ1(5D0) = 2.07 ms, τ2(5D0) = 8.07 ms and τ1(5D0) = 0.79 ms, τ2(5D0) = 9.76 ms for powders and glass‐ceramics, respectively) indicated the successful migration of optically active Eu3+ ions from amorphous silica framework to low phonon energy LaF3 nanocrystal phase. [ABSTRACT FROM AUTHOR]

Lead borate glasses doubly doped with Dy 3+ –Tb 3+ were investigated using optical spectroscopy: photoluminescence and decay time measurements. The main green emission band due to the 5 D 4 → 7 F 5 transition of Tb 3+ was observed under excitation of Dy 3+ . The energy transfer process from Dy 3+ to Tb 3+ occurs through nonradiative processes. The energy transfer efficiencies and transfer probabilities as a function of a square of the total rare earth ions concentration using Förster method were calculated. The nonlinear behavior of the energy transfer probability and the luminescence intensity ratio for a higher concentration of acceptor was studied taking into account the possible processes: concentration quenching and partial crystallization of the lead borate glasses. [ABSTRACT FROM AUTHOR]

The silica oxyfluoride materials doped with Eu 3+ ions have been obtained by a facile sol-gel method. The structure of xerogels and powders as well as derivative heat-treated at 350 °C phosphors was examined using scanning transmission electron microscopy (STEM), X-ray diffraction (XRD) measurements as well as FT-IR and Raman spectroscopy. Obtained results clearly indicate the formation of β-PbF 2 micro- and nanocrystalline phase dispersed in amorphous silica matrices during ceramization process. Importantly, it was observed that shape and size modifications of β-PbF 2 crystals are closely related to the quantitative composition of studied samples. Furthermore, the luminescence properties of Eu 3+ ions have been characterized based on excitation and emission spectra as well as luminescence decay measurements from the 5 D 0 excited state. The characteristic visible emission in reddish-orange spectral scope corresponding to the 4f 6 -4f 6 intra-configurational 5 D 0 → 7 F J (0-4) transitions has been observed before and after annealing process. The luminescence intensity R/O-ratios were also calculated. Obtained luminescence spectra and double-exponential character of decay curves measured for powders and glass-ceramic samples after heat-treatment indicated the significant changes in local crystal field around Eu 3+ ions. In result, conducted luminescence studies and structural characterization indicated the successfully migration of optically active Eu 3+ ions from amorphous silica framework to low-phonon energy β-PbF 2 micro-/nanocrystal phase after heat-treatment. [ABSTRACT FROM AUTHOR]

The 2 μm and upconversion emission in low phonon (805 cm −1 ) germanate glass and double-clad optical fibers co-doped with 0.7Yb 2 O 3 /(0.07–0.7)Ho 2 O 3 ions have been investigated. Glasses with the strongest emission intensity (0.7Yb 2 O 3 /0.15Ho 2 O 3 and 0.7Yb 2 O 3 /0.35Ho 2 O 3 ) were used as core of double-clad (DC) optical fibers and comparative analysis of their luminescent properties have been performed. The spectral overlapping between emission and absorption bands at near-infrared (2 μm) in glass and DC optical fibers caused red shifting with the increase of optical fiber length. Differences in luminescence spectra measured for bulk glass and double-clad optical fibers in both visible and near-infrared spectral ranges have been presented and discussed in details. [ABSTRACT FROM AUTHOR]

Technology of active glass-ceramics (GC) is an important part of luminescent materials engineering. The classic method to obtain GC is based on annealing of parent glass in proper temperature and different time periods. Generally, only the bulk materials are investigated as a starting host for further applications. However, the effect of an additional heat-treatment process on emission and structural properties during GC processing is omitted. Here, we focus on the possibility of obtaining transparent glass-ceramic doped with europium ions directly with a melt-quenching method. The influence of phosphate concentration (up to 10 mol %) on the inversion symmetry of local environment of Eu3+ ions in antimony-germanate-silicate (SGS) glass has been investigated. The Stark splitting of luminescence spectra and the local asymmetry ratio estimated by relation of (5D0→7F2)/(5D0→7F1) transitions in fabricated glass confirms higher local symmetry around Eu3+ ions. Based on XRD and SEM/EDX measurements, the EuPO4 nano- and microcrystals with monoclinic geometry were determined. Therefore, in our experiment, we confirmed possibility of one-step approach to fabricate crystalline structures (glass-ceramic) in Eu-doped SGS glass without additional annealing process. [ABSTRACT FROM AUTHOR]

Nanocrystalline β-PbF 2 phase singly-doped with Eu 3+ and Tb 3+ ions have been successfully synthesized using sol-gel technique and subsequent heat-treatment of xerogels at 350 °C. Thermal behavior and structural properties of obtained materials were studied using thermogravimetric analysis (TG), differential scanning calorimetry (DSC) as well as FT-IR and Raman techniques. XRD results confirmed formation of β-PbF 2 nanocrystals embedded in silica amorphous hosts after annealing at 350 °C. Moreover, the photoluminescence properties have been investigated based on excitation and emission spectra as well as decay analysis from the 5 D 0 (Eu 3+ ) and the 5 D 4 (Tb 3+ ) excited states. The sharp intraconfigurational 4f 6 −4f 6 and 4f 8 −4f 8 emission transitions assigned as the 5 D 0 → 7 F J (J=0–4) of Eu 3+ and the 5 D 4 → 7 F J (J=6-3) of Tb 3+ bands, respectively, were registered. The most prominent bands in studied xerogels and glass-ceramic materials are related to the following electronic transitions: 5 D 0 → 7 F 1 (orange) and 5 D 0 → 7 F 2 (red) (Eu 3+ ) as well as 5 D 4 → 7 F 5 (green) and 5 D 4 → 7 F 6 (blue) (Tb 3+ ). Thus, the R/O (Eu 3+ ) and G/B (Tb 3+ ) luminescence intensity ratios were calculated and analyzed. Luminescence decay kinetic clearly indicated a presence of two different surroundings around Eu 3+ and Tb 3+ dopants in β-PbF 2 -based glass-ceramic samples. In such singly-doped with Eu 3+ and Tb 3+ materials, the longer luminescence lifetimes (Eu 3+ : τ 1 ( 5 D 0 )=0.90 ms, τ 2 ( 5 D 0 )=5.15 ms; Tb 3+ : τ 1 ( 5 D 4 )=0.48 ms, τ 2 ( 5 D 4 )=4.01 ms) of an appropriate excited states were achieved in comparison to xerogel hosts (Eu 3+ : τ( 5 D 0 )=0.38 ms; Tb 3+ : τ( 5 D 4 )=0.49 ms). The obtained results indicate the incorporation of Eu 3+ and Tb 3+ ions into nanocrystalline phase during ceramization process. [ABSTRACT FROM AUTHOR]

In present work, thermal, structural and optical properties of un-doped Li 2 MgGeO 4 and lanthanide - doped Li 2 MgGeO 4 :Ln3+ (Ln = Er, Ho) germanate ceramics have been studied. Based on DSC measurements, two reversible phase transitions were verified during heating and cooling process of germanate ceramics. The results obtained from the Rietveld refinement indicate that Li 2 MgGeO 4 ceramics crystallize in monoclinic crystal lattice. Structural aspects were also evidenced by Raman and infrared spectroscopy. Emission investigations indicate that the most intense green bands due to the 4S 3/2 → 4I 15/2 (Er3+) and 5F 4 ,5S 2 → 5I 8 (Ho3+) transitions are well overlapped with broad band located near 500 nm. Broad green emission is attributed with the presence of magnesium in ceramic matrix. Based on literature data it can be assigned to F-type centers. • un-doped and lanthanide doped germanate ceramics have been studied. • Li 2 ZnGeO 4 ceramics crystallize in a monoclinic crystal lattice. • Intensive emission is due to 4S 3/2 → 4I 15/2 (Er3+) and 5F 4 ,5S 2 → 5I 8 (Ho3+) transitions. • Emission bands of Ln3+ are overlapped with broad green band of ceramic matrix. • Broad green emission is due to presence of magnesium and assigned to F-type centers. [ABSTRACT FROM AUTHOR]

Rare-earth-doped oxyfluoride germanate and borate glasses were synthesized and next studied using spectroscopic methods. Influence of fluoride modifier on luminescence properties of rare earths in different glass hosts was examined. The excitation and emission spectra of Pr3+ and Er3+ ions in the studied glasses were registered. The emission spectra of Pr3+ ions in germanate and borate glasses are quite different and depend strongly on the glass host. In samples doped with Er3+ ions emission bands located around 1530 nm corresponding to the main 4I13/2→4I15/2 laser transition were registered, independently of the glass host. Quite long-lived near-infrared luminescence of Er3+ ions was observed for germanate glasses with low BaF2 content, while in borate glass systems influence of barium fluoride on luminescence lifetimes is not so evident. The Judd-Ofelt calculations were used in order to determine quantum efficiencies of excited states of rare-earth ions in germanate and borate glasses. [ABSTRACT FROM AUTHOR]

Luminescent properties of silica sol–gel nanomaterials doped with Tb 3+ ions were studied and the results are presented. Compositions of the studied materials were varied while the terbium ions concentration was kept constant. Some technological parameters were analyzed and their pronounced effect on the photoluminescence properties is observed. Spectroscopic parameters of Tb 3+ ions were determined basing on excitation and emission measurements as well as on luminescence decay analysis before and after heat treatment process. The registered emission bands in the visible spectral range correspond to the 5 D 4 → 7 F J ( J =3−6) transitions of Tb 3+ ions. Intensities of the emission bands and luminescence decay curves of Tb 3+ ions depend on the excitation wavelength. Also, enhancement of the emission bands intensities and a significant increase of luminescence lifetime for the 5 D 4 excited state of Tb 3+ ions after heat treatment process was observed. The structure of obtained glasses was examined using X-ray diffraction (XRD), as well as FT-IR and Raman spectroscopic techniques. The obtained results indicate the incorporation of Tb 3+ ions into nanocrystalline phase during ceramization process. [ABSTRACT FROM AUTHOR]

The effects of selective components M 2 O 3 (M=Al, Ga) on local structure, thermal and spectroscopic properties of lead phosphate glasses doped with Er 3+ ions were systematically investigated. It was found that the both oxide modifiers (Al 2 O 3 and Ga 2 O 3 ) may be classified as crystallizing agents for lead phosphate glass host. The glass transition temperatures for glass samples modified by M 2 O 3 were determined using differential scanning calorimetry. The X-ray diffraction analysis was used in order to verify the nature of lead phosphate - based systems. Near-infrared luminescence spectra corresponding to 4 I 13/2 → 4 I 15/2 transition of erbium ions were measured. The luminescence spectra of Er 3+ -doped lead phosphate glass are presented and discussed in relation to the impact of crystallizing agents M 2 O 3 (M=Al, Ga). Luminescence lifetimes for the upper 4 I 13/2 laser state of Er 3+ ions were also evaluated. [ABSTRACT FROM AUTHOR]

Abstract: Lead borate glasses were prepared and then heat treated in order to obtain transparent glass-ceramics. Controlled crystallization of precursor lead borate glass at appropriate annealing temperature and time led to formation of the PbWO4 crystallites. The observed broad blue emission band is related to the PbWO4 crystallites. The influence of PbX2 content (X=F, Cl, Br), PbF2 concentration and lanthanide doping (Eu, Dy) on the excitation and emission spectra of lead borate glass-ceramics containing PbWO4 phase was examined. The relationship between Pb–X bond and spectral line width of the blue emission can be successfully observed, when halogen X ions (X=F, Cl or Br) are also present in the distorted PbWO4 crystallites. [Copyright &y& Elsevier]