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Novel ternary fluoro-germano-tellurite (GTS) glasses doped with Er3+ ions with 0.5 mol% and 1.0 mol% were fabricated by a conventional melt and quenching method and investigated using methods of optical spectroscopy. The room-temperature absorption spectrum was recorded and analyzed to determine radiative transition rates, radiative lifetimes, and branching ratios of Er3+ luminescence. Decay curves of Er3+ luminesccence were recorded and analyzed. Temperature dependences of emission spectra and absorption spectra in the region from RT (room-temperature) up to 675 K were studied in detail. The contribution of competing radiative and nonradiative processes to the relaxation of luminescent levels of Er3+ was assessed. Absolute and relative sensitivity were established utilizing the comprehensive model based on thermally coupled 2H11/2/4S3/2 excited states of erbium. The high quantum efficiency of the first erbium-excited state and value of gain coefficient indicate that GTS:Er glass system can be considered as conceivable NIR (near infrared) laser material as well. [ABSTRACT FROM AUTHOR]

Oxyfluorotellurite (65-x)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 –xLn 2 O 3 (Ln = Nd 3+ and Yb 3+ , x = 0.5, 2 and 5) and (65-x-y)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 –xNd 2 O 3 –yYb 2 O 3 (x = 0.5, y = 2 and x = 0.5, y = 5) glass systems were fabricated and their optical and thermal properties were investigated. Absorption and emission spectra of RE admixture ions in oxyfluorotellurite glasses were measured and examined at room temperature in the wide spectral region. Oscillator strengths, phenomenological Judd-Ofelt (J–O) intensity parameters, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. Luminescence decay curves of the 4 F 3/2 (Nd 3+ ) and 2 F 5/2 (Yb 3+ ) excited states were recorded and comprehensively analyzed for the single-doped Nd 3+ and Nd 3+ –Yb 3+ co-doped samples. Relaxation dynamics of luminescent levels were studied as a function of the Nd 3+ and Yb 3+ concentrations. An effective non-resonant phonon assisted energy transfer from neodymium to ytterbium was observed and studied. It was found that good thermal stability combined with proper spectroscopic parameters of examined Nd, Yb-doped oxyfluorotellurite glasses imply the suitability of these materials for the design of NIR-emitting efficient optical devices. Furthermore, the ability of the Nd 3+ ions in oxyfluorotellurite glass host as luminescent temperature sensor was verified. Relative intensity ratios of neodymium transitions originated in 4 F 7/2 / 4 F 3/2 and 4 F 5/2 / 4 F 3/2 thermally coupled closely-located excited states have been adequately determined and studied. [ABSTRACT FROM AUTHOR]

The paper shows some results related to thermal and optical properties of Eu 3+ -doped (65-x)TeO 2 -20ZnF 2 -12PbO-3Nb 2 O 5 -xEu 2 O 3 glass systems. Concentration of the Eu 2 O 3 was different (x = 0.5, 2 and 5 mol%) so it could determine the influence of active admixture on relevant properties of oxyfluorotellurite glass. Thermal stability and crystalline phases formed by the glass matrix were examined by differential thermal analysis (DTA). The characteristic temperatures (glass transition temperature and oxide glass crystallization temperature) have been determined. Optical absorption and emission spectra of Eu 3+ ions in oxyfluorotellurite glasses have been investigated at room temperature in the ultraviolet (UV), visible (VIS) and near-infrared (NIR) region. Oscillator strengths, phenomenological Judd-Ofelt intensity parameters Ω 2,4,6 , radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels have been also estimated. Lifetimes and the luminescence dynamics were studied as a function of the Eu 2 O 3 concentration. [ABSTRACT FROM AUTHOR]

Highlights: [•] Influence of temperature on optical properties of the Gd3Ga5O12:Sm single crystals. [•] Analysis of absorption and emission spectra as well as luminescence lifetimes. [•] Estimation of energies of crystal field components of Sm3+ in the Gd3Ga5O12 crystal. [•] Study on energy transfer phenomena using the classical Inokuti–Hirayama model. [ABSTRACT FROM AUTHOR]

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]

Abstract: Transparent single crystals of erbium-doped LaVO4 in form of platelets having an average size 0.5×2×2mm3 were obtained by the flux method using Pb2V2O7 as the solvent. Inductively coupled plasma (ICP) measurement revealed that the actual Er/La=0.3% molar ratio in the crystals is lower than Er/La=1% nominal molar ratio due to significant difference of ionic radii of La and Er. Luminescence spectra and luminescence decay curves for Er3+ transitions in the visible and near infrared region were recorded. Unpolarized Raman spectrum of undoped LaVO4 crystal was acquired, too. Up-converted green emission following excitation at 808 and 970nm was observed and dependence of its intensity on incident excitation power was determined. Based on experimental data gathered the relaxation dynamics of excited states of Er3+ was analyzed and mechanisms involved in the up-conversion phenomena were discussed. [Copyright &y& Elsevier]

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]

Sc2SiO5:4 at. %Tm crystal was obtained by the Czochralski method and the crystal cell parameters were calculated. Sixfold coordinated Sc-ions occupied two different crystallographic sites but the low temperature optical spectra only represented energy transitions originating from Tm ions residing in one site. Room temperature absorption spectrum was analyzed in the framework of Judd–Ofelt theory and the calculated absorption coefficient and cross section were 10.47 cm-1 and 5.55×10-21 cm2 at 791 nm respectively. Stimulated emission cross sections for the 3F4–3H6 transition near 1900 nm were evaluated using the reciprocity method while the luminescence 3F4 lifetime was measured to be 1.14 ms. We conclude that Tm:Sc2SiO5 is promising for diode-pumped infrared lasers. [ABSTRACT FROM AUTHOR]

Single crystal of La 3 Ga 5.5 Ta 0.5 O 14 (LGT) doped with Dy3+ was fabricated by the Czochralski technique and investigated employing methods of optical spectroscopy. Polarized optical absorption spectra and luminescence spectra were recorded at room temperature. Unpolarized absorption and luminescence spectra were recorded at 10 K. Spectra of blue luminescence related to transitions 4I 15/2 , 4F 9/2 → 6H 15/2 were recorded at several temperatures in the 300–773 K region. Dy3+ ions have the same symmetry sites in LGT but their spectra show inhomogeneous broadening due to structural disorder of the host and are markedly anisotropic. Results of the Judd-Ofelt treatment made it possible to assess emission cross sections for the 4F 9/2 → 6H 15/2 blue luminescence and for the 4F 9/2 → 6H 13/2 yellow luminescence employing Fuchtbauer-Ladenburg formula and reciprocity method. In particular, a spectral distribution of La 3 Ga 5.5 Ta 0.5 O 14 : Dy3+ σ-polarized luminescence band with an emission cross section σ em = 0.51 × 10−20 cm2 at 573.5 nm is favorable for a laser operation in the visible. Interpretation of the effect of temperature on the blue emission spectra leads to the conclusion that La 3 Ga 5.5 Ta 0.5 O 14 : Dy3+ is promising for application as luminescent thermometer. • Novel single crystal La 3 Ga 5.5 Ta 0.5 O 14 :Dy (LGT:Dy). • Detailed analysis of optical spectra and luminescence decay curves. • Potential visible laser operation at 573.5 nm. • Temperature sensitivity of LGT:Dy luminescence. [ABSTRACT FROM AUTHOR]

Optical, structural and morphological properties of Tm3+/Yb3+ co-doped NaYF 4 -based nano-glass-ceramic and a precursor glass have been investigated. The controlled heat-treatment of multicomponent oxyfluoride glass at 640 °C for 2 h was used to obtain crystalline precipitations. The differences in optical characteristics have been discussed analysing spectra recorded within wide VUV–VIS–NIR spectral range and considering relaxation dynamic of involved excited states. Optical spectra and luminescence decay curves were measured as a function of temperature in the range of 295–725 K. Based on up-converted emission spectra excited at 975 nm, temperature sensing properties of glass-ceramic were verified. The fluorescence intensity ratio between the up-converted emission bands located at around 795 nm (Tm3+:3H 4 –3H 6) and 695 nm (Tm3+:3F 3,2 –3H 6) was studied. The maximum relative temperature sensitivity was determined to be 0.35% K−1 at 445 K. • Tm3+,Yb3+ co-doped NaYF 4 -based oxufluoride nano-glass-ceramic. • Conversion of VUV excitation into thulium visible emission. • Impact of 295–725 K temperature on emission efficiency of Tm3+ and Yb3+. • Verification of Tm,Yb –co-doped glass-ceramic temperature sensor quality. [ABSTRACT FROM AUTHOR]

Samarium(2+) doped single crystals of SrCl 2 , SrBr 2 and SrI 2 with a nominal samarium concentration of 0.12, 0.16 and 0.13 at%, respectively, were grown by the Bridgman method. XRD examination revealed that obtained samples are single phase and their structures are consistent with those intentional. Based on preliminary spectroscopic measurement it was ascertained that Sm 2+ ions are incorporated without traces of Sm 3+ contamination. High resolution absorption, luminescence and excitation spectra as well as luminescence decay curves were measured as a function of temperature in the 4.2–300 K region. It was found that structural peculiarities of the host crystals affect strongly spectroscopic features of incorporated Sm 2+ ions. At room temperature all systems under study show a broad-band luminescence related to the parity allowed inter-configurational 4f 5 5d 1 – 4f 6 transitions of Sm 2+ . At 5 K a broad band luminescence vanishes in SrCl 2 :Sm 2+ and a resulting luminescence spectrum shows a rich fine structure consisting of narrow lines that we attribute to magnetic dipole transitions within the 4f 6 configuration of Sm 2+ ions located in centro-symmetric sites and/or their vibrational side bands. Based on an analysis of luminescence decay curves we attribute numerous narrow lines that appear in luminescence spectra of SrBr 2 :Sm 2+ recorded below 25 K to the 5 D 0 – 7 F J ( J = 0–4) intra-configurational transitions of Sm 2+ ions located in sites with C 4 and C 1 symmetry. A long-lived luminescence related to intra-configurational transitions was not observed in SrI 2 :Sm 2+ even at 4.2 K. [ABSTRACT FROM AUTHOR]

The paper shows results of investigation of thermal and optical properties of oxyfluorotellurite (65 − x )TeO 2 –20ZnF 2 –12Pb 2 O 5 –3Nb 2 O 5 – x Dy 2 O 3 ( x = 0.5, 2 and 5) glass systems. Thermal stability and the onset of crystallization of the materials were monitored by differential thermal analysis (DTA). It was found that characteristic parameters, namely glass transition temperatures ( T g ), onset of crystallization temperatures ( T c ) and thermal stability criteria Δ T and H ’ increased with increasing Dy 2 O 3 content indicating that the incorporation of dysprosium ions improves substantially thermal stability of glass system under study. Optical absorption and emission spectra of Dy 3+ ions in oxyfluorotellurite glass were investigated at room temperature in the visible (VIS) and near-infrared (NIR) region. Oscillator strengths, phenomenological Judd–Ofelt (JO) intensity parameters Ω 2,4,6 , radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. Decay curves of the 4 F 9/2 luminescence of incorporated Dy 3+ ions were recorded and analysed. Lifetimes and the luminescence dynamics were studied as a function of the Dy 2 O 3 concentration. It was concluded that good thermal stability combined with desirable spectroscopic parameters of investigated dysprosium-doped oxyfluorotellurite glass point at the suitability of this material for the design of UV-excited visible phosphors. [ABSTRACT FROM AUTHOR]