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This paper reports the spectroscopic properties of praseodymium-doped potassium lutetium double phosphates, KLuP2O7:Pr3+(1%). Spectra of photoluminescence (PL), PL excitation, X-ray excited luminescence and pulse cathodoluminescence, thermally stimulated luminescence were measured. KLuP2O7:Pr3+ showed Pr3+ emission connected both with high intensity interconfigurational 4f15d1→4f2 transitions (UV bands in region of 250-320 nm), intraconfigurational 4f2→4f2 transitions (weak lines in vision spectral region) and Stocks defect-related luminescence. Upon both UV intra-center and band-to-band excitation with ionizing radiation, emission spectra of KLuP2O7:Pr3+ are dominated by Pr3+ interconfigurational 4f1 5d1→4f2 radiative transitions. Luminescence decay kinetics measurements established decay time τ ≈ 19 ns at room temperature. The study of thermally stimulated luminescence demonstrates effective light storage. Parameters of charge carriers' traps were calculated: ΔE1 = 1.1 eV (for peak at 352 K) and ΔE2 = 1.3 eV (for peak at 388 K). [ABSTRACT FROM AUTHOR]

The present work reports, structural and luminescence studies on Eu3+ ions doped telluroborate glasses for red laser applications. The local structure and vibronic spectral analysis were performed in order to correlate them with the local field environment of Eu3+ ions on the basis of Raman and Phonon sideband spectroscopy. The Nephelauxetic intensity ratios (β) and bonding parameter (δ) values obtained from the absorption bands reveal the covalent nature of the Eu–O bond. The increasing Ω2 intensity parameters and R values confirms the higher asymmetry around Eu3+ ions and the covalency of Eu–O. The Judd-Ofelt (JO) intensity parameters were used to estimate the radiative properties such as transition probability (A), stimulated emission cross-section(σEP) branching ratio values (β) and radiative lifetimes (τR) for the observed emission transitions. [ABSTRACT FROM AUTHOR]

In the present work, Eu3+ ions doped boro-phosphate glasses (xEuBKP) were successfully prepared by melt quenching technique and their luminescence properties were investigated through recording optical absorption and photoluminescence spectral measurements. From the absorption spectral data, the optical band gap energy (Eopt) corresponding to the direct and indirect allowed transitions of the title glasses has been determined. The Judd-Ofelt (JO) intensity parameters Ωλ (λ=2, 4 and 6) were calculated from the emission spectra to analyse the symmetry of the ligand environment around Eu3+ ions and to examine the nature of the bond between Eu3+ ions and ligand oxygen in the prepared glasses. From the JO intensity parameters, radiative properties such as transition probability (A), stimulated emission cross section (σEP) radiative life time (τcal) and branching ratios (βR) of the studied glasses were determined and the suitability of the present Eu3+ doped boro-phosphate glasses for optoelectronic applications were discussed based on the obtained results. [ABSTRACT FROM AUTHOR]

Spectra of photoluminescence (PL) and X-ray excited luminescence (XRL) in region of 350 - 850 nm, PL excitation spectra in UV-VUV region (112 - 400 nm), thermally stimulated luminescence and absorption spectra were studied in SrF2 crystals doped with Er3+ ions. Intra-configurational radiative f-f transitions were studied at room temperature, 90 and 8 K under excitation with energy Eexc: a) in fundamental absorption region (Eexc ≥ Eg); b) in intracenter excitation region (Eexc < Eg); c) in infrared region (Eexc << Eg) with using laser 980 nm diode as exciting photons (up-conversion processes). The probability of radiative transitions from excited states of the impurity Er3+ center depends on energy of exciting photons. Up-conversion luminescence was studied in temperature interval from 90 to 460 K. While changing the temperature, intensity of main transitions (4S3/2 → 4I15/2, 4F9/2 → 4I15/2) changes. At high temperature (T > 387 K) a new low-energy transition 4I9/2 → 4I15/2 was detected. The presented results can be used as reference for spectroscopy of f-f radiation transitions in Er3+ ion in wide spectral range of exciting photons in crystals with fluorite-type structure. [ABSTRACT FROM AUTHOR]

Cr-doped GdAlO3 (Cr:GdAlO3) is shown to produce remarkably high-intensity spin-allowed broadband luminescence with sufficiently long decay times to make effective luminescence-decay-time-based temperature measurements above 1000 °C. This phosphor is therefore an attractive alternative to the much lower luminescence intensity rare-earth-doped thermographic phosphors that are typically utilized at these elevated temperatures. In particular, Cr:GdAlO3 will be preferred over rare-earth-doped phosphors, such as Dy:YAG, at temperatures up to 1200 °C for intensity-starved situations when the much lower emission intensity from rare-earth-doped phosphors is insufficient for accurate temperature measurements in the presence of significant radiation background. While transition-metal-doped phosphors such as Cr:Al2O3 (ruby) are known to exhibit high luminescence intensity at low dopant concentrations, quenching due to nonradiative decay pathways competing with the 2E to 4A2 radiative transition (R line) has typically restricted their use for temperature sensing to below 600 °C. Thermal quenching of the broadband 4T2 to 4A2 radiative transition from Cr:GdAlO3, however, is delayed until much higher temperatures (above 1000 °C). This spin-allowed broadband emission persists to high temperatures because the lower-lying 2E energy level acts as a reservoir to thermally populate the higher shorter-lived 4T2 energy level and because the activation energy for nonradiative crossover relaxation from the 4T2 level to the 4A2 ground state is high. The strong crystal field associated with the tight bonding of the AlO6 octahedra in the GdAlO3 perovskite structure is responsible for this behavior. [ABSTRACT FROM AUTHOR]

Improving the up-conversion efficiency is the key issue in tellurite glasses. The quantum efficiency, radiative transition rate and lifetimes of excited states are greatly influenced by the optical properties of the host material, ligand field, multiphonon relaxation processes, impurities, temperature and concentration of erbium ions. We develop a comprehensive 4-level model to examine the radiative and nonradiative (NR) decay processes for the green (4S3/2→4I15/2) and red (4F9/2→4I15/2) emission over a temperature range of (10-340 K) and concentration range of (0.1-4.5 mol.%). Concentration dependent enhancement and thermal quenching of efficiency for up-conversion is investigated using the derived rate equations. These features are attributed to the NR energy transfer processes, trapped impurity effects, and thermal assisted hopping. The unusual nature of temperature and concentration dependent quenching effects for green and red emission is queries for further investigations. It is further suggested that to achieve higher infrared to visible up-converted efficiency in tellurite glasses the NR channels for energy and charge transfer by phonon and impurity mediated process has to be minimized. Our results on pump power dependent emission intensity, quantum efficiency, luminescence intensity, radiative lifetimes, and transition probabilities are in conformity with other experimental findings. [ABSTRACT FROM AUTHOR]

The CaF2:0.83 mol% ErF3 crystal was grown using the vertical Bridgman method. The Judd-Ofelt intensity parameters Ω2, Ω4, and Ω6 for f-f transitions of Er3+ ions were determined from the optical absorption spectrum. The predicted radiative lifetimes are compared to those of Er3+ transitions reported in various hosts. Apart from the green and red emission, reported by other researchers, an UV (314 nm) emission band was observed, not reported before. [ABSTRACT FROM AUTHOR]

The CaF2:0.83 mol% ErF3 crystal was grown using the vertical Bridgman method. The Judd-Ofelt intensity parameters Ω2, Ω4, and Ω6 for f-f transitions of Er3+ ions were determined from the optical absorption spectrum. The predicted radiative lifetimes are compared to those of Er3+ transitions reported in various hosts. Apart from the green and red emission, reported by other researchers, an UV (314 nm) emission band was observed, not reported before. [ABSTRACT FROM AUTHOR]