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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]

• GeO 2 -TiO 2 -BaO-BaF 2 -Ga 2 O 3 system doped with Er3+, Tm3+, Ho3+ were synthesized. • The extremely low IR absorption coefficients were achieved. • Enhanced emission at 1.5 µm, 1.8µm and 2.0 µm by introducing BaF 2 in the composition was observed. • The luminescence lifetime significantly increased in the function BaF 2. • Optimal BaF 2 content in titanate-germanate glass was evaluated. A novel TiO 2 -GeO 2 -BaO-BaF 2 -Ga 2 O 3 glasses doped with rare-earth were synthesized, and the impact of the substitution of BaF 2 for BaO on properties has been investigated by luminescence spectroscopy. The IR absorption coefficient is extremely low, which is attractive for optical fibers emitting NIR radiation. Near-IR luminescence associated to the Er3+:4I 13/2 → 4I 15/2 (FWHM = 108 nm), Tm3+:3F 4 → 3H 6 (FWHM = 244 nm) and Ho3+:5I 7 → 5I 8 (FWHM = 179 nm) transitions are enhanced in the presence of BaF 2. Luminescence lifetimes increase with increasing content of BaF 2 in the glass composition. Fabricated optical materials with relatively high BaF 2 content represent a good starting point for further investigations in the field of glass technology and modern photonics. [ABSTRACT FROM AUTHOR]

Luminescence properties of olivine-type germanate phosphors with general formula Li 2 AGeO 4 :0.5Er3+ (A = Zn, Mg) have been studied. Olivine-type materials prepared via conventional solid-state reaction method were examined for down- and up-conversion luminescence processes. In the down-conversion process after 381 nm excitation, two strong green emission bands due to 2H 11/2 /4S 3/2 → 4I 15/2 transitions of Er3+ were registered, with a change in the intensity ratio depending on the ceramic matrix. Weak red emission bands related to 4F 9/2 → 4I 15/2 transition were also recorded. In contrast, luminescence bands behaved completely differently for the up-conversion process after infrared excitation at λ exc = 980 nm. Red emission bands were much more significant than green emission bands. These effects are stronger for Li 2 MgGeO 4 :0.5Er3+ than Li 2 ZnGeO 4 :0.5Er3+. In the red and green spectral range, slope values for both matrices Li 2 AGeO 4 :0.5Er3+ (A = Zn, Mg) confirmed two-photon process. • Phosphors Li 2 AGeO 4 :Er3+ (A = Zn, Mg) with olivine structure were studied. • Down/up conversion luminescence processes of Er3+ ions were examined. • Intensities of green/red emission bands depend strongly on the excitation wavelengths. • Two-photon up-conversion process in Li 2 AGeO 4 :Er3+ (A = Zn, Mg) was confirmed. [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]