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A series of the Tb- and Dy-doped glasses with Li2O--2B2O3 (or Li2B4O7:Tb and Li2B4O7:Dy) composition were synthesised and their spectroscopic properties were investigated. The Li2B4O7:Tb and Li2B4O7:Dy glasses of high chemical purity and optical quality were obtained from corresponding polycrystalline compounds in the air using standard glass technology. The Tb and Dy impurities were added to Li2B4O7 composition in the form of Tb2O3 and Dy2O3 oxide compounds in amounts of 0.5 and 1.0 mol%. The electron paramagnetic resonance (EPR), luminescence excitation and emission spectra of the Li2B4O7:Tb and Li2B4O7:Dy glasses were investigated. On the basis of EPR and photoluminescence spectra analysis it was shown that the Tb and Dy impurities are incorporated in the Li2B4O7 glass network as Tb3+ (4f8, 7F6) and Dy3+ (4f 9, 6H15/2) ions, exclusively. All observed transitions of the Tb3+ and Dy3+ centres in the luminescence excitation and emission spectra were identified. The luminescence kinetics shows single exponential decay for Tb3+ and Dy3+ centres in Li2B4O7 glasses. The lifetime values for main emission transitions of the Tb3+ and Dy3+ centres in the Li2B4O7 glasses containing 0.5 and 1.0 mol% Tb2O3 and Dy2O3 are determined at T = 300 K. Peculiarities of optical properties and local structure of the Tb3+ and Dy3+ centres in the Li2B4O7:Tb and Li2B4O7:Dy glasses as well as their potential applications have been discussed. [ABSTRACT FROM AUTHOR]

Optical absorption, luminescence excitation, and emission spectra as well as luminescence kinetics of the Sm- and Yb-doped glasses with lithium tetraborate (Li2B4O7) composition were investigated and analysed. The Sm- and Yb-doped lithium tetraborate glasses of high optical quality were obtained in air from corresponding polycrystalline compounds according to standard glass synthesis technology. The Sm and Yb impurities were added to the Li2B4O7 compound in the form of Sm2O3 and Yb2O3 oxides in amount of 0.4 mol%. Using optical and electron paramagnetic resonance spectroscopy it was shown that the Sm and Yb impurities are incorporated into the lithium tetraborate glass network as Sm3+ (4f5, 6H5/2) and Yb3+ (4f13, 2F7/2) ions, exclusively. All of the observed transitions in the absorption and luminescence spectra of Sm3+ and Yb3+ centres were identified. The luminescence kinetics of the Sm3+ and Yb3+ centres in the Li2B4O7 glass are characterised by a single exponential decay. Decay constants for the main emission transitions of the Sm3+ and Yb3+ centres in the lithium tetraborate glass were obtained at T = 300 K. Incorporation peculiarities and optical spectra of Sm3+ and Yb3+ ions in the lithium tetraborate glass have been discussed in comparison with other borate glasses and crystals. [ABSTRACT FROM AUTHOR]

The 50GeO2-(50-x-y)PbO-yPbF2-xLnF3 glass single doped with Pr3+ and Tb3+ ions was studied. The composition of the material was modified by varying the content of both PbF2 (y = 5, 10, 15 mol%) and LnF3 (x = 0.2 and 2 mol%). The differential thermal analysis (DTA) of as-melted samples was used to determine thermal characteristics. Optical techniques and kinetics measurements were used to monitor the effect of thermal treatment on spectroscopic properties and dynamics of luminescent states of optically-active ions in amorphous and two-phase systems. It was found that non-exponential decays of praseodymium luminescence in as-melted material become exponential or nearly exponential with corresponding longer lifetimes in thermally-treated samples. This effect was not so strong in the Tb3+-doped glass. The influence of the PbF2 content on luminescence dynamics was studied for samples doped with 2 mol% of Pr3+. It was observed that the increase of PbF2 content leads to lengthening of luminescence lifetime, e.g., the 1D2 lifetime increases from 4.1 to 45 µs in 5 and 15 mol% of PbF2 as-melted samples, respectively. [ABSTRACT FROM AUTHOR]

Oxyhalide lead borate glasses doped with rare earth ions have been studied before and after thermal treatment. The rare earths as optically active ions were limited to the Er3+ ions. Near-infrared luminescence due to the main 4I13/2-4I15/2 laser transition of Er3+ was registered. The introduction of PbX2 to the borate glass results in a reduction of spectral linewidth and an increase of luminescence lifetime of 4I13/2 state of Er3+ ions. The unusual large spectral linewidth for 4I13/2-4I15/2 transition of Er3+ in the oxide glass host was obtained, whereas the luminescence decay from 4I13/2 state is longer for a sample with PbF2 than PbCl2 and PbBr2. Heat treatment introduces transformation from a glass to transparent glass-ceramic (TGC). The coordination sphere around Er3+ ions is changed, giving important contribution to the luminescence characteristics. The spectroscopic consequence of this transformation is the increase of luminescence lifetime and the narrowing of spectral lines of Er3+. [ABSTRACT FROM AUTHOR]

Oxyfluoride lead borate glasses singly doped with Nd3+ and Er3+ ions have been studied before and after thermal treatment. The orthorhombic PbF2 crystallites are formed during thermal treatment, which was evidenced by X-ray diffraction analysis. Near-infrared luminescence spectra at 1.06 µm and 1.53 µm have been registered for samples before and after annealing, which correspond to the main 4F3/2-4I11/2 and 4I13/2-4I15/2 laser transitions of Nd3+ and Er3+ ions, respectively. Luminescence decays from 4F3/2 state of Nd3+ and 4I13/2 state of Er3+ have been analyzed in detail. Contrary to Nd-doped samples, the luminescence lines obtained for Er-doped transparent oxyfluoride glass-ceramics are more intense and narrowed, whereas the luminescence decays from 4I13/2 state of Er3+ are slightly longer in comparison to precursor glasses. [ABSTRACT FROM AUTHOR]

Optical absorption and luminescence spectra as well as luminescence kinetics of the Nd3+ centres in glasses with Ca3Ga2Ge3O12:Nd composition, containing 0.2 and 1.0 wt% of the Nd2O3 were presented and analysed. The oscillator strengths and phenomenological intensity parameters Ωt (Ω2, Ω4, and Ω6) were obtained using standard Judd-Ofelt theory. Calculated Ωt parameters, radiative transitions rates, branching ratios and radiative lifetime for Nd3+ centres in the glass with Ca3Ga2Ge3O12 composition were analysed and compared with corresponding Nd3+ parameters in their crystalline analogue with garnet structure. Experimental lifetimes are compared with those calculated, and quantum efficiency of Nd3+ centres from 4F3/2 emitting level in the glass with Ca3Ga2Ge3O12 composition is estimated. Incorporation peculiarities and local structure of Nd3+ luminescence centres in the glass with Ca3Ga2Ge3O12 composition and corresponding Ca3Ga2Ge3O12:Nd3+ garnet laser crystals are considered. On the basis of extended X-ray absorption fine structure (EXAFS) spectra (L3-edge) of rare-earth elements analysis it has been shown that Nd3+ luminescence centres in the CaO-Ga2O3-GeO2 glass network occupy structural sites with the coordination number to oxygen N = 6. [ABSTRACT FROM AUTHOR]

Energy transfer processes in lead borate glasses doubly doped with Yb-Tm and Yb-Er have been investigated at room temperature under excitation of Yb at 975 nm. The non-resonant energy transfer from ²F5/2 state of Yb to ³H5 state of Tm results in up-converted emission at 850 nm due to the ³H4-³H6 transition of thulium ions. The nearly resonant transfer from ²F5/2 state of Yb to 4I11/2 state of Er results in green up-conversion and near-infrared emission, which correspond to the 4S3/2-4I15/2 and 4I13/2-4I15/2 transitions of erbium ions, respectively. High Yb concentration in both co-doped samples is required for optimal energy transfer efficiency (η > 90%). Results with the singly Yb-doped samples are also presented to clarify the energy transfer process. [ABSTRACT FROM AUTHOR]

Glasses with composition 50 GeO2-(45 - x)PbO-5PbF2 - xLnF3 (Ln = Nd or Sm, x = 0.2 and 2 mol%) were synthesised in the bulk form. Phase profiles and temperature characteristics were measured by differential thermal analysis (DTA); glass transition temperature Tg, as well as the β-PbF2Tβ and oxide glass crystallisation Tc temperatures have been derived for each individual system. A study of optical properties (absorption, emission) of the PbF2 - Nd3+ and PbF2 - Sm3+ was carried out. The oscillator strengths were obtained for several optical transitions and they have been used to calculate phenomenological intensity parameters Ω2, 4, 6. The probabilities of radiative transitions from fluorescent levels of Nd3+ and Sm3+ ions, as well as branching ratios and radiative lifetimes, were estimated on the basis of the Judd-Ofelt framework. The fluorescence dynamics of studied systems was measured. Experimental lifetimes were compared and discussed with those obtained with the Judd-Ofelt theory. [ABSTRACT FROM AUTHOR]

The 50GeO2-(50-x-y)PbO-yPbF2-xLnF3 glass single doped with Pr3+ and Tb3+ ions was studied. The composition of the material was modified by varying the content of both PbF2 (y = 5, 10, 15 mol%) and LnF3 (x = 0.2 and 2 mol%). The differential thermal analysis (DTA) of as-melted samples was used to determine thermal characteristics. Optical techniques and kinetics measurements were used to monitor the effect of thermal treatment on spectroscopic properties and dynamics of luminescent states of optically-active ions in amorphous and two-phase systems. It was found that non-exponential decays of praseodymium luminescence in as-melted material become exponential or nearly exponential with corresponding longer lifetimes in thermally-treated samples. This effect was not so strong in the Tb3+-doped glass. The influence of the PbF2 content on luminescence dynamics was studied for samples doped with 2 mol% of Pr3+. It was observed that the increase of PbF2 content leads to lengthening of luminescence lifetime, e.g., the 1D2 lifetime increases from 4.1 to 45 µs in 5 and 15 mol% of PbF2 as-melted samples, respectively. [ABSTRACT FROM AUTHOR]