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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]

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]

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]

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]

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]

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]

Highlights: [•] Tb-doped heavy metal glasses were studied as a function of glass composition. [•] Excitation and luminescence spectra of Tb ions in heavy metal glasses were examined. [•] Luminescence intensity ratios (G/B) and measured lifetimes of Tb were determined. [•] Correlation between G/B factor, measured lifetimes and energy phonon was proposed. [ABSTRACT FROM AUTHOR]

An investigation of the structural and luminescent properties of the transparent germanate glass-ceramics co-doped with Ni2+/Er3+ for near-infrared optical fiber applications was presented. Modification of germanate glasses with 10–20 ZnO (mol.%) was focused to propose the additional heat treatment process controlled at 650 °C to obtain transparent glass-ceramics. The formation of 11 nm ZnGa2O4 nanocrystals was confirmed by the X-ray diffraction (XRD) method. It followed the glass network changes analyzed in detail (MIR—Mid Infrared spectroscopy) with an increasing heating time of precursor glass. The broadband 1000–1650 nm luminescence (λexc = 808 nm) was obtained as a result of Ni2+: 3T2(3F) → 3A2(3F) octahedral Ni2+ ions and Er3+: 4I13/2 → 4I15/2 radiative transitions and energy transfer from Ni2+ to Er3+ with the efficiency of 19%. Elaborated glass–nanocrystalline material is a very promising candidate for use as a core of broadband luminescence optical fibers. [ABSTRACT FROM AUTHOR]

In this work, the series of Tb3+/Eu3+ co-doped xerogels and derivative glass-ceramics containing CaF2 nanocrystals were prepared and characterized. The in situ formation of fluoride crystals was verified by an X-ray diffraction technique (XRD) and transmission electron microscopy (TEM). The studies of the Tb3+/Eu3+ energy transfer (ET) process were performed based on excitation and emission spectra along with luminescence decay analysis. According to emission spectra recorded under near-ultraviolet (NUV) excitation (351 nm, 7F6 → 5L9 transition of Tb3+), the mutual coexistence of the 5D4 → 7FJ (J = 6–3) (Tb3+) and the 5D0 → 7FJ (J = 0–4) (Eu3+) luminescence bands was clearly observed. The co-doping also resulted in gradual shortening of a lifetime from the 5D4 state of Tb3+ ions, and the ET efficiencies were varied from ηET = 11.9% (Tb3+:Eu3+ = 1:0.5) to ηET = 22.9% (Tb3+:Eu3+ = 1:2) for xerogels, and from ηET = 25.7% (Tb3+:Eu3+ = 1:0.5) up to ηET = 67.4% (Tb3+:Eu3+ = 1:2) for glass-ceramics. Performed decay analysis from the 5D0 (Eu3+) and the 5D4 (Tb3+) state revealed a correlation with the change in Tb3+–Eu3+ and Eu3+–Eu3+ interionic distances resulting from both the variable Tb3+:Eu3+ molar ratio and their partial segregation in CaF2 nanophase. [ABSTRACT FROM AUTHOR]

In this work, we performed a systematic analysis of the impact of selected chemical reagents used in sol-gel synthesis (i.e., N,N-dimethylformamide) and different catalyst agents (i.e., CH3COOH, HNO3) on the formation and luminescence of Eu3+-doped SiO2–LaF3 nano-glass–ceramics. Due to the characteristic nature of intra-configurational electronic transitions of Eu3+ ions within the 4f6 manifold (5D0 → 7FJ, J = 0–4), they are frequently used as a spectral probe. Thus, the changes in the photoluminescence profile of Eu3+ ions could identify the general tendency of rare earth materials to segregate inside low-phonon energy fluoride nanocrystals, which allows us to assess their application potential in optoelectronics. Fabricated sol-gel materials, from sols to gels and xerogels to nano-glass–ceramics, were examined using several experimental techniques: X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR), and luminescence measurements. It was found that the distribution of Eu3+ ions between the amorphous silicate sol-gel host and LaF3 nanocrystals is strictly dependent on the initial composition of the obtained sols, and the lack of N,N-dimethylformamide significantly promotes the segregation of Eu3+ ions inside LaF3 nanocrystals. As a result, we detected long-lived luminescence from the 5D0 excited state equal to 6.21 ms, which predisposes the obtained glass–ceramic material for use as an optical element in reddish-orange emitting devices. [ABSTRACT FROM AUTHOR]