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Neodymium doped fluorophosphate (FP:Nd3+) glasses with different chemical compositions (59NH4H2PO4+15ZnO +15BaF2+10X+1·0NdF3 (X=LiF, NaF, CaF2, SrF2, AlF3)) were prepared by melt quenching. Their structures and spectroscopic properties were studied using x-ray diffraction, FTIR, FT-Raman and 31P, 27Al MAS NMR techniques. Various structural groups were identified using FTIR and FT-Raman spectra. The depolymerisation of metaphosphate chains are described by the decrease of Q² tetrahedral sites allowing the formation of pyrophosphate groups revealed by 31P MAS NMR spectroscopic studies. Optical properties were studied using absorption and photoluminescence spectroscopy. Judd–Ofelt intensity parameters Ωλ (λ=2, 4 and 6) were estimated from absorption spectra. Radiative parameters such as transition probabilities (A), radiative lifetimes (τR), integrated absorption cross-sections (Σ) and branching ratios (βR) were calculated. Two emission lines at 1060 and 1330 nm were observed for Nd3+ in all the fluorophosphate glasses. From the emission spectra, emission characteristics were studied via optical band gains (σe×τR)and gain bandwidths (σe×Δλeff). Fairly large numerical values for peak emission cross-sections (σe) and branching ratios (β) for 4 F3/2→4 I11/2 transition of Nd3+ ion doped calcium fluorophosphate glass were observed. These results are rosy for NIR laser application at 1060 nm. [ABSTRACT FROM AUTHOR]

In this work, the visible luminescence of P 2 O 5 -KF-Al 2 O 3 glasses with Tm 2 O 3 was studied. The Tm3+ ion can have a strong blue emission, which allows the development of LEDs in this color region. This study refers to the synthesis of oxyfluorophosphate glasses, 38P 2 O 5 +(50-x)KF+12Al 2 O 3 +xTm 2 O 3 (PKAl:Tm), with x = 0.25, 0.50, 0.75, and 1.00 mol%, by the melt-quenching method. The prepared materials showed amorphous characteristics verified by XRD data. The absorption spectra shown six main bands characteristic of Tm3+ ions, from ground state 3H 6 to excited levels 3F 4 , 3H 4 , 3H 5 , 3F 3,2 , 1G 4 and 1D 2 , in which the intensities increased with the concentration of Tm 2 O 3. In the FTIR spectra, it was verified that the profiles of the PKAl samples are similar to glasses based on phosphate systems. The Judd-Ofelt parameters were calculated, where for PKAl glasses the trend was Ω 2 >Ω 4 >Ω 6. The excitation spectra of PKAl:Tm glasses shown an intense band centered at 358 nm (3H 6 →1D 2). The luminescence spectra with excitation at 358 nm shown two bands at 453 nm (1D 2 →3F 4), and 480 nm (1G 4 →3H 6); the highest emission intensity was observed to the sample doped with 0.75 mol% of Tm 2 O 3. The calculated CIE diagram shown that the doped samples have coordinates close to the primary blue color, which favors the application for the development of blue LEDs and wLEDs. The decay curves for the 1D 2 level were fitted by single exponential with lifetime values decreasing with increasing concentration of Tm 2 O 3. These results show that the PKAl:Tm glasses are potential candidates for applications in LEDs. [Display omitted] • 38P 2 O 5 -(50-x)KF-12Al 2 O 3 -xTm 2 O 3 glasses, x = 0.25, 0.50, 0.75, and 1.00 mol%. • The optical parameters, transition probability and radiative lifetimes were evaluated using the Judd-Ofelt theory. • CIE coordinates appeared in the deep blue regions under 357 excitation, with main emission at 454 nm. • Oxyflorophosphate glasses doped with Tm 2 O 3 are candidates for photonic applications in blue emitters. [ABSTRACT FROM AUTHOR]

Abstract: The spectroscopic properties of tellurite glasses of composition (in mol%) TNKNd: (70− x)TeO2–15Nb2O5–15K2O–xNd2O3 (x =0.1, 1.0, 1.5, 2.0 and 2.5) and TNLNd10: 69TeO2–15Nb2O5–15Li2O–1.0Nd2O3 and lithium metaborate glass of composition LBNNd10: 89LiBO2–10Nb2O5–1.0Nd2O3 have been investigated using absorption and emission spectra and decay curve analysis. An energy level analysis has been carried out considering the experimental energy positions of the absorption and emission bands, using the free-ion Hamiltonian model. The spectral intensities have been calculated by using the Judd–Ofelt theory and in turn the radiative properties such as radiative transition probabilities, emission cross-sections, branching ratios and radiative lifetimes have been estimated. The decay curves at the lower concentrations are exponential while they show a non-exponential behavior at higher concentrations (⩾1.0mol%) due to energy transfer processes. The effective lifetimes for the 4F3/2 level are found to decrease with increase in Nd2O3 concentration for all the glasses under investigation. The non-exponential decay curves have been well-fitted to the Yokota–Tanimoto model with S =6, indicating that the nature of energy transfer is of dipole–dipole type and energy migration also plays an important role. The results obtained have been compared with Nd3+-doped phosphate, fluorophosphate, lead borate, tellurite, germanate and silicate glasses and Nd3+-doped YAG ceramic and Ca2Nb2O7 crystals. [Copyright &y& Elsevier]

Abstract: This article reports the effect of mixed alkalis on the optical absorption and emission spectra of Sm3+ and Dy3+ doped chloroborate glass matrices of the compositions 69.5B2O3 xLiCl(30− x)NaCl0.5R2O3 and 69.5B2O3 xLiCl(30− x)KCl0.5R2O3 (where R=Sm and Dy and x =5, 10, 15, 20 and 25). Using Judd–Ofelt theory, the spectral intensities and Judd–Ofelt intensity parameters (Ω 2, Ω 4 and Ω 6) were obtained from the measured absorption bands of the spectra. Using these intensity parameters, total radiative transition probabilities (A T), radiative lifetimes (τ R), branching ratios (β) and peak emission cross-sections (σ P) were obtained for the two rare earth ions in these two glass matrices. Variation of these parameters with x in the glass matrix has been discussed. It is found that for Sm3+ ion, the transition, 4G5/2 → 6H9/2 shows highest emission cross-section and is maximum at x =10mol% in lithium–sodium and at x =20mol% in lithium–potassium glass matrices. For Dy3+ ion, the transition, 4F9/2 → 6H13/2 shows highest emission cross-section and is maximum at x =20mol% in lithium–sodium and at x =10mol% in lithium–potassium glass matrix. [Copyright &y& Elsevier]

Abstract: Structural and spectroscopic properties of neodymium doped sodium borate and fluoroborate glasses of composition (in mol%) (99− X) B2O3 + XNa2O+1Nd2O3, X =49.5, 39.5 and 29.5 and 49.5B2O3 + XNa2O+(49.5− X) NaF+1Nd2O3, X =0 and 24.75 have been investigated using XRD, FTIR, absorption and emission spectra and decay curve. The XRD of the glasses confirm their glassy nature and the FTIR spectra reveal the presence of BO3 and BO4 units along with the strong OH− groups in the glasses. The UV–vis-NIR absorption spectra were used to calculate the bonding parameters ( and δ), to identify the ionic/covalent nature of the glasses. The spectral intensities have been calculated by using Judd–Ofelt analysis and inturn used to estimate radiative properties such as radiative transition probabilities, radiative lifetimes, branching ratios, peak stimulated emission cross-sections. Branching ratios and stimulated emission cross-sections show that the 4F3/2 → 4I11/2 transition of the glasses under investigation has the strong emission around 1060nm. The decay from the 4F3/2 level of Nd3+ ions is found to be single exponential. Multiphonon relaxation and quenching due to OH− groups play a governing role in the luminescence quenching of 4F3/2 level of Nd3+ ions in the titled glasses. The results obtained are compared with reports on similar glasses. [Copyright &y& Elsevier]

Abstract: The fluorophosphate glasses with the composition (mol%) of (56− x)P2O5 +17K2O+(12− x)MgO+6MgF2 +9Al2O3 + xNd2O3 and (56− x)P2O5 +17K2O+(12− x)SrO+6SrF2 +9Al2O3 + xNd2O3 (where x =0.1, 1.0, and 2.0mol%) have been prepared and characterized by absorption and luminescence spectra and decay curve analysis. The absorption band positions of Nd3+ ions have been analyzed using the free-ion Hamiltonian model. From the absorption spectra, Judd–Ofelt intensity parameters have been evaluated which are in turn used to predict radiative properties such as total radiative transition probabilities, radiative lifetimes and branching ratios. The present glasses have high stimulated emission cross-sections, implying that they have potential for laser applications. Lifetime of the 4F3/2 level decreases with increasing Nd3+ ions concentration. The non-exponential decay curves have been fitted to the generalized Yokota and Tanimoto model and derived energy transfer and migration parameters, donor–acceptor coupling constants and diffusion coefficients. The free OH content in the 1.0mol% Nd2O3-doped glasses has been estimated from their measured Fourier transform infrared transmittance spectra. [Copyright &y& Elsevier]

Abstract: This paper reports the optical properties of Dy3+ in sodium fluoroborate glasses of the type XNaF·(89− X)B2O3·10 Al2O3·1Dy2O3 (where X =8, 12, 16, 20 and 24). Judd–Ofelt intensity parameters (Ω 2, Ω 4, Ω 6) are derived from the absorption spectra. The Judd–Ofelt theory has been applied to interpret the local environment of Dy3+ ions and bond covalency of RE–O bond. These parameters have been used to calculate radiative transition probabilities (A rad), lifetimes (τ R) and branching ratios (β R) for the excited level 4F9/2. The predicted values of τ R are compared with the measured values for 4F9/2 level for five glass compositions (Glass (A–E)). The stimulated emission cross-section σ(λ P) are also evaluated for the 4F9/2 → 6H J (J =11/2, 13/2, and 15/2) transitions. [Copyright &y& Elsevier]

Using the melt-quenching method, Dy3+-doped lithium-strontium-zinc-borate glasses of composition 20Li 2 O–5SrO–5ZnO–(70- x)B 2 O 3 – x Dy 2 O 3 (0 ≤ x ≤ 1.25 mol%) were prepared and characterised using various tools. The Dy3+ contents dependent spectroscopic traits of these glasses were determined to identify their white light-emitting potential. The Judd-Ofelt (JO) evaluation was made to validate the experimentally measured optical properties. The XRD patterns of the as-quenched samples revealed their glassy nature and the FTIR spectra exhibited the presence of BO 3 and BO 4 functional groups. The absorption spectra of the samples showed twelve characteristic bands of Dy3+ wherein the hypersensitive one occurred at 1270 nm. The JO intensity parameters revealed a changing trend from Ω 2 > Ω 4 > Ω 6 to Ω 2 > Ω 6 > Ω 4 , indicating the effectiveness of Dy3+ doping. The photoluminescence emission spectra of the glasses exhibited the three significant peaks (intense blue, intense yellow and weak red) with concentration quenching beyond 1 mol% of Dy3+. The radiative parameters of 4F 9/2 → 6H 13/2 transition disclosed the highest branching ratio (≥85%), radiative transition probability of 504–1711 s − 1 , stimulated emission cross-section from 28.70 × 10 − 22 − 19.01 × 10 − 22 cm 2 , optical bandwidth of 1.34 × 10 − 20 − 4.63 × 10 − 20 cm 3 and optical gain of ~ 14.5 × 10 − 25 cm 2 s , suggesting optical energy harnessing potential of the proposed glass composition which are useful in low threshold and efficient lasers and amplifiers design. The quantum efficiency of the glasses was ranged from 34–84%. The 1931 CIE analyses of the samples disclosed the colour coordinates appearance very close to the pure white (within 1–10%) with colour purities ranged from 11.6 to 4.8%, and the estimated values of CCT were above 5300 K, indicating their potency for the cool white light emission. • Dy3+ doped borate-based glasses were developed. • Spectroscopic, radiative and colourimetric quantities were evaluated. • The determined colour coordinates are in pure white light region. • The achieved CCT values are in cool white light region. • The attained white light purity records deviation of 11.6–4.8% from natural white light (0%). [ABSTRACT FROM AUTHOR]

Usually, it is difficult to quantitatively express the optical transition properties of Yb3+ in powdered samples owing to the difficulty in measuring the absolute absorption spectra. In this work, we developed an approach for confirming the absorption and emission cross section spectra and the radiative transition rates for the absorption and emission transitions between 2F 7/2 and 2F 5/2 states of Yb3+. The proposed approach was examined for Yb3+ in Er3+/Yb3+ co-doped NaYF 4 powders. The absorption cross section for 2F 7/2 → 2F 5/2 transition and emission cross section for 2F 5/2 → 2F 7/2 transition of Yb3+ in NaYF 4 :Er3+/Yb3+ were confirmed. Meanwhile, the transition rates for the absorption and emission transitions were also calculated. A route for calculating the radiative transition rate, absorption and emission cross sections of Yb3+ in powdered samples is proposed. Furthermore, the radiative transition properties of Yb3+ in NaYF 4 :Er3+/Yb3+ phosphor derived from an auto-combustion-assisted fluoridation was studied via our proposed route. Image 1 • NaYF 4 : Er3+ and NaYF 4 : Er3+/Yb3+ phosphors were prepared via an auto-combustion assisted solid-state reaction. • A new calculation method of radiation transition rates of Yb3+ was proposed and used for Er3+/Yb3+ co-doped NaYF 4 powders. • The absorption cross section spectra of Er3+/Yb3+ co-doped NaYF 4 and Er3+ doped NaYF 4 powders were confirmed. • The absorption and emission cross sections of Yb3+ in NaYF 4 were derived. • The transition rates of Yb3+ for the absorption (2F 7/2 → 2F 5/2) and emission (2F 5/2 → 2F 7/2) transitions were calculated. [ABSTRACT FROM AUTHOR]

Multi-component phosphate glasses with various Nd 2 O 3 content have been prepared using conventional melt-quenching technique. X-ray diffraction was carried out to study the structure of the prepared samples and it was found that all the obtained samples are amorphous. Electrostatic F (2) , F (4) , F (6) , and spin–orbit parameters have been determined from the absorption spectra. Judd-Ofelt theory has been used to analyze and evaluate the radiative transition probability, branching ratio, and radiative lifetime for the metastable level 4 F 3/2. Luminescence spectra and experimental lifetimes give information regarding the absence of chemical clustering and suggest that the physical clustering is negligible making the glass a suitable candidate for photonic applications. Image 1 [ABSTRACT FROM AUTHOR]