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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]

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]

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]

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]

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 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]

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]

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]