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A new borate solid solution series of powders, Li 6 Eu 1-x Sm x (BO 3 ) 3 (LSEBx, x = 0.35, 0.5, 0.6, 1), were synthesized by solid-state reaction, characterized and their luminescent properties were investigated. The absorption spectra indicate that absorption takes place mainly from the Sm 3+ 6 H 5/2 ground state, with a strong band at 405 nm. The photoluminescence spectra reveal that the Eu 3+ red emission intensity strongly depends on the Sm 3+ content x. Judd–Ofelt theory was applied to experimental data for the quantitative determination of phenomenological parameters Ωi (i = 2, 4, 6) Judd Ofelt parameters, radiative transition rates and emission quantum efficiency. Owing to the energy transfer from Sm 3+ to Eu 3+ the intense red light detected at 613 nm at room temperature under UV or blue light excitation, was improved by ∼35% as compared with Sm 3+ -free samples. This energy transfer was confirmed by faster decay times of Sm 3+ as energy donors. Moreover, the energy transfer between Sm 3+ and Eu 3+ is unidirectional and irreversible, implying that the energy transfer wastage between Sm 3+ and Eu 3+ is very low. Magnetic susceptibility (χ) measurements of LSEBx were carried out in the temperature range 2–320 K and are used to compare calculated and experimental energy levels. [ABSTRACT FROM AUTHOR]

A study of the optical, spectral-luminescent and holographic properties of the chlorine-containing photo-thermo-refractive (PTR) glass doped with neodymium ions was carried out. The chlorine-containing PTR glass has been recently produced by replacing the bromine in the standard PTR glass with chlorine. The glass was doped with different concentrations of neodymium ions. The spectroscopic analysis of neodymium in the glass has been performed using the Judd-Ofelt theory based on experimental absorption and emission measurements. Spectroscopic parameters, such as the Judd-Ofelt intensity parameters, radiative and non-radiative transition probabilities, fluorescence lifetimes, stimulated emission cross-sections, and branching ratios, were obtained and found to be comparable with the parameters of the standard PTR glass doped with neodymium. The mechanism of non-radiative energy transfer was analyzed based on the lifetime kinetics measurements. It was found that cross-relaxation among neodymium ions is the dominant non-radiative energy transfer mechanism. Holographic characteristics of the chlorine-containing PTR glasses doped with neodymium have been also studied. The volume Bragg grating was recorded in the doped and undoped glasses. It was found that the UV exposure and heat treatment do not change the spectroscopic characteristics of neodymium ions in the glasses, while the neodymium ions reduce the sensitivity of the glass. The energy transfer from cerium to neodymium when irradiating using the 325-nm laser makes the hologram recording possible on the samples of low neodymium concentrations only. Studying the spectroscopic and holographic properties of the chlorine-containing PTR glass doped with neodymium ions demonstrates the potential of using such a material in the applications of photonics integration and monolithic optical devices like distributed-feedback lasers. • Spectroscopic properties of Nd ions in Cl-PTR glass are comparable to those of Nd in the standard (Br-PTR) glass. • VBG was recorded in the undoped Cl-PTR glass, as well as in the glass doped with Nd. • UV exposure and heat treatment do not affect the spectral-luminescent properties of Nd in the Cl-PTR glass. • Nd reduces the photosensitivity of Cl-PTR due to energy transfer from Ce to Nd during the hologram recording at 325 nm. [ABSTRACT FROM AUTHOR]

This paper investigated the mid-infrared luminescence properties of Er 3+ /Ho 3+ co-doped tellurite germanate glass at 2 μm pumped by 980 nm. Thermal stability of the system, absorption spectra and fluorescence spectra of the Er 3+ /Ho 3+ co-doped glass sample were measured. Besides, the absorption spectra of the Ho 3+ singly doped sample was measured. According to the measured absorption spectra and the Judd–Ofelt theory, the Judd–Ofelt intensity parameters Ω t ( t = 2, 4, 6), spontaneous radiative transition probability, branching ratio and lifetime of Ho 3+ were calculated. And the upconversion emission in Er 3+ doped and Er 3+ /Ho 3+ co-doped tellurite germanate glasses pumped by 980 nm have been investigated. Then the spectroscopic properties and possible energy transfer mechanisms between Ho 3+ and Er 3+ ions were discussed in detail. Meanwhile, the FWHM (146 nm), σ e peak × FWHM (659.92 cm 3 ) and emission cross section (4.52 × 10 −21 cm 2 ) of 5 I 8 → 5 I 7 transition of Ho 3+ were obtained, respectively. The results indicate that Er 3+ /Ho 3+ co-doped tellurite germanate glass is a promising host material for 2 μm solid laser. [ABSTRACT FROM AUTHOR]

Er 3+ /Ce 3+ co-doped and B 2 O 3 modified tellurite glasses with initial composition of TeO 2 –GeO 2 –Li 2 O–Nb 2 O 5 were prepared using melt-quenching technique for potential applications in Er 3+ -doped fiber amplifiers (EDFAs) and lasers. The absorption spectra, fluorescence spectra, up-conversion spectra, Raman spectra and differential scanning calorimeter (DSC) curves of glass samples were measured to evaluate the effect of B 2 O 3 modification on the 1.53 μm band spectroscopic properties of Er 3+ , structural nature and thermal stability of glass hosts. It was shown that the introduction of an appropriate amount of B 2 O 3 oxide can further improve the 1.53 μm band fluorescence emission through an enhanced phonon-assisted energy transfer (ET) from Er 3+ to Ce 3+ ions under the excitation of 980 nm, and the quantitative studies were carried out to elucidate the ET mechanism via calculating the microscopic parameters and phonon contribution ratios. Meanwhile, the thermal stability of glass hosts increases slightly with the introduction of B 2 O 3 oxide. Furthermore, the 1.53 μm band optical signal amplification was simulated based on the rare-earth ion rate and light power propagation equations. An increment in signal gain by about 1.4 dB at 1532 nm was observed in the Er 3+ /Ce 3+ co-doped tellurite glass fiber containing 6 mol% amount of B 2 O 3 oxide, and the maximum signal gain reaches to 31 dB on a 50 cm fiber pumped at 980 nm with power 200 mW. The present results indicate that the prepared Er 3+ /Ce 3+ co-doped tellurite glass modified by an appropriate amount of B 2 O 3 oxide has good prospect as a gain medium applied for 1.53 μm band EDFAs and lasers. [ABSTRACT FROM AUTHOR]

A mechanism of energy transfer sensitization in Eu-doped LiAl 5 O 8 produced by the modified sol-gel method is proposed. The XRD results show the formation of the desired crystalline phase and the solubility limit of Eu dopant. Based in the PL results, a mechanisms of energy transfer (ET) and simultaneous excitation (SE) between the doping ion (Eu3+) and contaminating ions (Cr3+ and Fe3+) were elaborated based in the five possible dynamics. The first attributed to SE between Eu3+- Fe3+ characterized by direct excitation of Eu3+ and Fe3+ ions. The second is attributed to ET between Eu3+-Cr3+, attributed to the radiative transitions 5D 0 →7F 1,2 and Cr3+ ion. Third mechanism is similar to the energy transfer described by the second mechanism in addition to Fe3+ sensitization. The fourth and fifth are due to the SE between Eu3+-Fe3+-Cr3+. • A mechanism of energy transfer sensitization in Eu-doped LiAl 5 O 8 is proposed. • Simultaneous excitation (SE) between the Eu 3+ and contaminating ions (Cr 3+ and Fe 3+ ) were elaborated. • The effects of the Eu 3+ dopant concentration on the structural and optical properties also were investigated. [ABSTRACT FROM AUTHOR]

Highlights: [•] The fluorescence properties of 2.7μm emission and energy transfer mechanism are investigated. [•] The optimized concentration ratio of Er3+ to Ho3+ is found to be 1:1. [•] The sample possesses large emission cross section and radiative transition probability. [•] The energy transfer microparameters are calculated and discussed. [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: Ho3+/Yb3+ codoped lanthanum–tungsten–tellurite (TWL) glasses are prepared by melt-quenching method. The Judd–Ofelt intensity parameters (Ωt t =2, 4, 6), radiative transition rates, radiative lifetimes, and branching ratios of Ho3+ are calculated based on the absorption spectrum to evaluate the spectroscopic properties of Ho3+ in TWL glass. The mid-infrared emission of the samples are investigated under the excitation of 980nm LD. The absorption, emission cross-sections and gain coefficient of Ho3+:5I7 → 5I8 are calculated. The energy transfer processes of Yb3+–Yb3+ and Yb3+–Ho3+ are analyzed, the results show that the Yb3+ ions can transfer their energy to Ho3+ ions with large energy transfer coefficient, and a maximum efficiency of 84%. [ABSTRACT FROM AUTHOR]

Abstract: Fluorophosphates glasses YF3–BaF2–Ba(PO3)2 doped with Er3+ and Er3+–Yb3+ were prepared and the structures of the samples were briefly investigated. The experimental intensity parameters were calculated according to the Judd–Ofelt theory, from which the radiative transition probabilities, fluorescence branching ratios, and radiative lifetimes of Er3+ were obtained. Bright green and red upconversion emissions was observed in Er3+–Yb3+ co-doped samples excited by 980nm laser diode, and two-photons absorption processes were determined for the emissions by examining the dependence of the emission intensity on the excitation power. The concentration effects on the intensity and decay time of the upconversion emission revealed that growing Er3+ concentration declined the probability of sequential energy transfer from Yb3+ to Er3+, and thus increasing the intensity ratio of the red emission to the green ones. The temperature effects on the intensity ratios of different emission bands showed that the maximum transducer sensitivity based on the fluorescence intensity ratio (FIR) was calculated to be 0.0015/°C at 6°C. [Copyright &y& Elsevier]

A new series of optically translucent borosilicate glasses activated with varying concentrations of Dy3+ ions were fabricated by employing melt quenching method. Spectral investigations were conducted by recording the absorption, photoluminescent (PL) excitation and PL emission for Dy3+ activated borosilicate glasses. The absorption spectral information was exposed to Judd-Ofelt (J-O) analysis to calculate various radiative properties such as transition probability, total transition probability, branching ratios and radiative lifetimes of the as synthesized glasses. The excitation spectrum recorded under 483 nm emission wavelength possess a sharp peak at 348 nm in 0.1 mol% of Dy3+ ions doped borosilicate glass. Emission spectra recorded for all the Dy3+ ions activated borosilicate glasses under 348 nm intense excitation wavelength exhibit two potential peaks in visible region at 483 nm (4F 9/2 → 6H 15/2) and 575 nm (4F 9/2 → 6H 13/2). The emission centered at 483 nm is most prominent. Radiative properties measured from the absorption spectral feature were correlated with emission spectral information to estimate emission cross-section, gain bandwidth and optical gain parameters to understand the utility of the as synthesized glasses as photonic devices. The CIE coordinates measured for all the titled glasses are in good proximity with the white light coordinates of CIE 1931 diagram. • LPZABS glasses with Dy3+ ions were prepared by using melt quench technique. • XRD recorded for all the as prepared glasses confirm the glassy nature. • The bonding nature between Dy3+ ions and the surrounding ligands is ionic in nature. • Energy transfer through dipole-dipole interaction leads to concentration quenching. • CIE of 1.5mol% of Dy in LPZABS glasses are in proximity with CIE of white light. [ABSTRACT FROM AUTHOR]

We report the luminescence and energy transfer features in (B 2 O 3) 0.55-x (Li 2 O) 0.30 (MgO) 0.10 (Gd 2 O 3) 0.05 (Sm 2 O 3) x glasses, prepared via melt-quenching rout. By employing the Judd–Ofelt (JO) theory, the spectral parameters such as oscillator strengths, stimulated emission cross-sections, radiative transition probability and branching ratios are evaluated from the absorption and emission spectra. The dipole-dipole interaction as a dominant interaction mechanism is confirmed from Inokuti–Hirayama (IH) model. The luminescent color falls in the orange part of commission International de I'Eclaiage (CIE). The ultra-violet (UV) sensitization of visible emission of Sm3+ is analyzed by the photoluminescence (PL) emission spectra and the lifetime measurement. The Gd: 6P 7/2 –8S 7/2 emission in UV range and the Sm3+:4G 5/2 –6H J luminescence at 598 nm were observed upon the excitation of Gd:4f level by λ exc = 275 nm. Moreover, the impact of energy transfer on the donor-acceptor luminescence, quantum efficiency, and donor luminescence decay kinetics are investigated. It is found that efficient orange luminescence originates from Sm3+ emitting centers. These findings show that these as-prepared luminescent glasses are promising in orange LEDs and laser applications. Schematic excitation, emission (a) and ETC mechanism (b) in the energy level diagram of Gd3+ and Sm3+ in the LMgGBSm samples. Image 1 • ➢Prepared borate glasses co-doped with Gd3+ and Sm3+ via melt quenching technique. • ➢PL excitation and emission spectra showed concentration quenching at 0.3 mol% Sm 2 O 3. • ➢Enhanced Sm3+ and diminished Gd3+ luminescence confirmed energy transfer from Gd3+ to Sm3+. • ➢The energy transfer nature verified from lifetime's decay of Inokuti–Hirayama (IH) model. • ➢95% quantum efficiency was found in LMgGBSm0.3 sample for its 4G 5/2 level of Sm3+ ions. [ABSTRACT FROM AUTHOR]