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In this work, the effect of growth temperature (678–988 °C) on silicon oxycarbide (SiC x O y) samples obtained by hot filament chemical vapor deposition (HFCVD) is reported. The samples were deposited on silicon (Si) n-type (100) and quartz substrates for optical and structural studies. At a lower temperature (678 °C), silicon oxycarbide powders were formed on Si substrates due to the homogeneous reaction occurring in the gas phase. However, for temperatures between 804 and 988 °C, silicon oxycarbide films were formed on Si substrates. By changing the temperature from 678 to 988 °C, both carbon (C) concentration (21.2–17.7 wt.%) and the relative percentage of Si–C bond density (%Rt Si-C = 11.34–3.47 %) decreased, as demonstrated by EDS and FTIR measurements, respectively. On the other hand, the content of relative Si– O –Si bonds located around 1060 cm−1 remained dominant in all cases, resulting in SiC x O y films with an amorphous SiO x -type structure. These films exhibited strong photoluminescence (PL) centered in the blue region (∼3 eV), where Si–NOVS radiative centers were preferentially responsible for PL emission. At a lower temperature (678 °C), the PL intensity decreased. The determination of optical bandgap energy (E opt) using Tauc Plots coincided with the emission due to luminescent centers (∼3 and ∼2.7 eV) observed in PL, indicating that the radiative transitions were due to defects. The AFM measurements showed an increase in roughness from 5.01 to 16.20 nm as the growth temperature decreased, as expected according to SEM measurements. [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]

The understanding of how radiative transition probabilities change with temperature is crucial for comprehending the relationship between fluorescence behavior and temperature. However, although various models have been proposed to explain the patterns of transition probabilities (A) with temperature changes, they lack consistency due to their derivation from distinct microscopic perspectives. In this study, the macroscopic law of the temperature-dependent A for the 4G 5/2 , 4F 9/2 , and 5D 0 energy states in YVO 4 :Re3+(Re3+=Sm3+, Dy3+ and Eu3+) was obtained. Three rare earth ions (Re3+) were identified for each with unique energy level properties conducive to validating the general rules of A. These ions share a common characteristic: in the visible spectrum, their main emissions originate from the radiative transitions from the same higher energy level (4G 5/2 in Sm3+, 4F 9/2 in Dy3+, and 5D 0 in Eu3+) to lower energy levels, respectively. The A of the main emission levels, varying with T , were obtained by fitting the fluorescence decay curves. The exponential law governing non-radiative transitions was revealed after separating the radiative transition rate (W R) from A. The macroscopic law of temperature-dependent transition probabilities of 4G 5/2 , 4F 9/2 , and 5D 0 energy states in YVO 4 :Ln3+ (Ln3+ = Sm3+, Dy3+ and Eu3+) has been found to follow the Boltzmann distribution. The results indicate that the non-radiative transitions of the main emission levels of the rare-earth ions are processes from the excited state to adjacent lower energy levels. This macroscopic pattern may serve as a foundational rule for understanding the impact of microscopic factors on A. • The macroscopic law of temperature-dependent transition probabilities of 4G 5/2 , 4F 9/2 , and 5D 0 energy states in YVO 4 :Ln3+ (Ln3+ = Sm3+, Dy3+ and Eu3+) has been found to follow the Boltzmann distribution. • The results indicate that the non-radiative transitions of the main emission levels of the rare-earth ions are processes from the excited state to adjacent lower energy levels. [ABSTRACT FROM AUTHOR]

A group of highly Er3+-doped TeO 2 –BaF 2 –LaF 3 –La 2 O 3 fluorotellurite glasses was prepared by high-temperature melting and rapid cooling. The Judd-Ofelt (J-O) theory intensity parameters, radiative transition rate, and radiative lifetime of Er3+ ions were calculated based on the absorption spectra. The luminecence spectra at 2.7 μm and luminescence lifetime curves of Er3+ ions in fluorotellurite glasses, excited at 980 nm, were studied. The fluorotellurite glass exhibits high infrared transmittance (88 %), excellent thermal stability (ΔT > 105 °C), and low phonon energy (781 cm-1). According to Fuchbauer-Ladenburg theory, the absorption and emission cross sections of Er3+-doped fluorotellurite glass at 2.7 μm are 5.50×10−21 and 6.28×10−21cm2, respectively. These findings suggest that the glass holds significant potential for applications in mid-infrared (MIR) fiber lasers. • The fluorotellurite glass possesses high infrared transmittance (88 %). • The prepared glass exhibits excellent thermal stability (ΔT > 105 °C). • The prepared glass has low phonon energy (781 cm-1). • The fluorotellurite glass exhibits strong luminescence at 2.7 μm. [ABSTRACT FROM AUTHOR]

Herein, zinc sodium borate glasses containing samarium ions were fabricated using the traditional melt-quenching approach and explored using several spectroscopic and structural methods. The XRD data corroborated the host glass specimen's non-crystalline nature. Scanning electron microscopy and the energy dispersive X-ray spectroscopy method were utilized to study the morphological and homogenous attributes. The UV–Vis–NIR wavelengths of absorption showed a total of seventeen distinct Sm3+ ion peaks. The three transitions 4G 5/2 → 6H 9/2 , 6H 7/2 , and 6H 5/2 are evident in the PL data at wavelengths of 644, 597, and 561 nm, respectively, in the red, reddish-orange, and greenish-yellow zones. The luminescence intensity of the investigated glass specimens increases up to 0.4 mol% Sm3+ ion content thereafter reducing because of the non-radiative transfer of energy. The estimated JO intensity parameters exhibit a trend of Ω 2 >Ω 4 >Ω 6. The trend of the assessed radiative parameters also demonstrated that they are sensitive to changes in the glass network. The Futchbauer-Ladenburgh theory was used to compute the emission cross-section of various transitions utilizing the radiative parameters. The 1931 CIE chromaticity coordinates assessments corroborate the reddish-orange luminescence from the fabricated glasses. The outcomes have proven that obtained BNZSm x glasses doped with low concentrations of trivalent samarium ions are well suited for reddish-orange solid-state lighting systems. [Display omitted] • The efficacy of low-concentration Sm3+ ions on spectroscopic features of alkali zinc borate glasses has been studied. • Electronic structure and morphological features were ascertained for the studied glass specimens. • Judd-Ofelt attributes were investigated for 0.4 mol% doped ZnNaB glass. • The results revealed that the 0.4 mol% of Sm3+ doped ZnNaB glasses are beneficial for solid state lighting devices. [ABSTRACT FROM AUTHOR]

We report on a modification of the Judd-Ofelt theory accounting for thermal populations of Stark sub-levels of the multiplets involved in transitions in absorption and emission. The calculations require the data on the crystal-field splitting, the irreducible representations of Stark sub-levels and the selection rules for electric-dipole transitions. Simple formulas for absorption oscillator strengths and probabilities of radiative spontaneous transitions are obtained. The application of the proposed model allowed us to remove the contradiction between the transition intensities in absorption and emission (3H 6 ↔ 3F 4) for Tm3+-doped crystals. It was also used to explain the experimental temperature dependences of luminescence lifetimes of the 3F 4 Tm3+ manifold in two widely used laser crystals, LiYF 4 and Y 3 Al 5 O 12. The case of Yb3+ ions featuring a small number of crystal-field sub-levels is also considered. • Judd-Ofelt theory accounting for thermal populations of Stark sub-levels. • Simple formulas for absorption strengths and radiative transition probabilities. • The contradiction between Tm3+ absorption and emission transition intensities is resolved. • Temperature dependence of luminescence lifetimes of the 3F 4 Tm3+ manifold. • The case of Yb3+ ions featuring a small number of crystal-field sub-levels is considered. [ABSTRACT FROM AUTHOR]

0.5 mol% of europium (Eu3+) doped bismuth phosphate glasses (BiP) with different contents (0, 5, 10 and 15 mol%) of bismuth and different (0.1, 0.3, 0.5, 1.0, 1.5 and 2.0) mol% of Eu3+ doped 5 mol% bismuth contained BiP glasses were made by melt-quenching technique. The structural and photoluminescence properties were analysed via FT-Raman, excitation, luminescence and decay time computations. Judd-Ofelt (J-O) parameters were evaluated from the emission spectra and also various radiative properties such as radiative transition probabilities (A R), radiative lifetimes (τ rad), stimulated emission cross-sections (σ e), branching ratios (β), optical gain bandwidths (σ e xΔλ eff) and optical gain (σ e xτ rad) values for the observed emission transitions are studied. The electron-phonon coupling constants (g), phonon energies (hω) and the multiphonon relaxation rates (W MPR) were determined. The decay curves of 5D 0 level of Eu3+ in all the studied glasses exhibit single exponential nature. The lifetimes are obtained from the decay curves and reported. The CIE chromaticity co-ordinates were computed and they have fallen in red region. The characteristic red luminescence emission around 612 nm for 5D 0 →7F 2 transition confirmed that the Eu3+ doped BiP glasses might be useful to fabricate red lasers and display devices. Image 1 ➢ Eu3+ doped bismuth phosphate glasses have been prepared and characterised. ➢ Phonon energy (1228 cm−1) of the Eu-0.5 glass has been estimated by analyzing PSB and PET. ➢ BiP:Eu-0.5 glass exhibit higher values of σ e , β exp , Δλ eff , σ e xΔλ eff , σ e xτ rad and η. ➢ BiP:Eu glass is a novel material for the development of red lasers. [ABSTRACT FROM AUTHOR]

Large-sized, high optical quality Gd 2 O 3 single crystals were grown from a solution at T = 1145 °C using Czochralski method. XRD analysis showed that the crystal structure is characterized by a single cubic (bixbyite) phase (c -phase). The absorption spectra and luminescence properties of Gd 2 O 3 doped with Eu3+ and Tb3+ impurity ions were studied. The absorption spectrum of Gd 2 O 3 :Eu in the short wavelength region is mainly due to charge transfer transitions from O2− to Eu3+ (240–290 nm), which overlap with the Urbach tail of the host-absorption. Additionally, electronic transitions in Eu3+ (320–540 nm) and Gd3+ (245–315 nm) lanthanide ions contribute to the absorption spectrum. Intraconfigurational radiative f – f transitions in impurity ions are clearly observed upon both UV- and X-ray excitations. However, 6 P J → 8 S 7 / 2 radiative transitions in Gd3+ ions are completely unobservable. Based on the obtained spectroscopic data, the energy positions of the ground state of all di- and trivalent lanthanide ions, as well as the energies of intraconfigurational f – f and interconfigurational f – d electronic transitions in Gd 2 O 3 crystals with a cubic structure, are calculated. The proposed electronic energy diagram is used to discuss efficient energy transfer between lanthanide ions. [Display omitted] • We grew optical quality Gd 2 O 3 single crystals from flux using Czochralski method. • XRD analysis of the Gd 2 O 3 crystals showed monophase cubic structure. • We studied intraconfigurational f – f transitions upon UV and X-ray excitations. • We determined the lowest energy levels of Ln2+ and Ln3+ ions in Gd 2 O 3 crystals. • We revealed efficient energy transfer between lanthanide ions in Gd 2 O 3 crystals. [ABSTRACT FROM AUTHOR]

In this study, we used hard X-ray-excited optical luminescence (XEOL) to investigate the emission properties of MgAl 2 O 4 wafers with a crystal orientation of (100), (110), or (111). MgAl 2 O 4 (110) exhibited the lowest XEOL emission intensity because the (110) orientation is thermochemical unstable and therefore unfavorable for generating oxygen vacancies. By fitting XEOL spectra, we identified 13 and 6 clear emission peaks corresponding to the color centers in MgAl 2 O 4 wafers and the 2E g →4A 2g radiative transition of Cr ion impurities, respectively. Using an X-ray nanoprobe, we obtained an X-ray fluorescence spectroscopy (XRF) map of the elemental distribution of Cr with 100 nm spatial resolution. X-ray absorption spectroscopy (XAS) revealed that the valence state of the Cr ion impurities was Cr3+. We thus also clearly demonstrate the advantages of combining XEOL, XRF, and XAS in the X-ray nanoprobe beamline by obtaining emission spectra using XEOL and using XRF and XAS to analyze elemental distributions and valence states to further elucidate the emissions of samples. • The emission properties of the color centers in MgAl 2 O 4 wafers has been investigated by XEOL. • We identified 13 clear emission peaks corresponding to the color centers in MgAl 2 O 4 wafers. • X-ray absorption spectroscopy (XAS) revealed that the valence state of the Cr ion impurities was Cr3+. [ABSTRACT FROM AUTHOR]

Synthesis and characterization of calcium tungstate-based micro-nanophosphors are reported in the present work. These materials were synthesized by spray pyrolysis technique. According to Scanning Electron Microscopy measurements, CaWO 4 and CaWO 4 :Eu (III) have quasi-spherical shape. CaWO 4 presents blue luminescence whose origin is an electron transition within unperturbed W O 4 2 − complexes, while CaWO 4 :Eu (III) luminescent properties are generated by the presence of Eu (III) ions, which produced light emissions at 591, 615, 655, and 702 nm. Such emissions are due to radiative transitions from the excited state 5D 0 to 7F j (j = 1, 4) inter-level transitions within Eu (III) electronic energy states. These phosphors were blended with a commercial 3D print photocurable resin (Sain Smart 101-90-840TS) and their luminescent properties were transferred to resin. Besides in this case, blended 3D resin has an intrinsic blue luminescence due to its π and π* bonds which is activated under 380 nm excitation wavelength, however blended 3D resin can be also activated under 465 nm excitation which only activates Eu (III) ions producing a red emission 3D luminescent photocurable resin. • CaWO 4 :Eu(III) phosphors synthesized by spray pyrolysis technique. • Phosphors functionalized with 2-thenoyltrifluoroacetone (TTA). • Energy transfer from TTA to Eu (III) ions. • Incorporation of functionalized phosphors into commercial 3D printing photocurable resin. [ABSTRACT FROM AUTHOR]

An addition of Eu3+ ions in Borate glasses (7TiO 2 + 3Al 2 O 3 + (60−x)B 2 O 3 + xEu 2 O 3 + 5LiCO 3 + 25SrCO 3) (where x = 0.05, 0.10, 0.15, and 0.20 mol%) and Boro-phosphate glasses (40B 2 O 3 + 3Al 2 O 3 + (10−x)P 2 O 5 + xEu 2 O 3 + 7ZnO + 5LiCO 3 + 10H 6 NO 4 P + 25SrCO 3) (where x = 0.10 and 0.20 mol%) containing heavy metals, alkali, and alkaline were prepared using a conventional melt quenching technique. The complementary study of the FT-IR and FT-Raman spectroscopic studies proposed the conversion of BO 3 ⇔ BO 4 in the borate glass network, and the exchange of the PO 3 ⇔ PO 2 in the boro-phosphate glass network by increasing the Eu3+ ion concentration. The optical characteristics including absorption, linear refractive index (n), Urbach energy (E u), direct and indirect band gap energies of the prepared glasses were examined and discussed. Judd-Ofelt (JO) theory was used to determine radiative spectroscopic properties such as radiative transition probability (A R), luminescence branching ratio (β R) and stimulated emission cross-section (σ P E). Theoretically, the optical gain parameter and gain bandwidth were calculated, which shows their vital role in laser applications. Using CIE chromaticity coordinates, the reddish orange light emission was observed as a proportion of the increase in Eu3+ ions concentration in both glass networks. The measured colour coordinates were utilised to evaluate the correlated colour temperature (CCT), colour purity (P c), and excitation purity (P e) of the studied glasses. [Display omitted] • Eu3+ ions in the range of 0.05–0.20 mol% are successfully doped in borate and boro-phosphate glass matrices and studied. • The η of BPEu(0.10) is 87.8% and σ p E of BEu (0.20) is 11 × 10−22 cm2 is higher than other prepared glasses. • All the spectroscopic studies confirm the prepared glasses could be suitable for optoelectronic device applications. [ABSTRACT FROM AUTHOR]

Polycrystalline ceramics of lithium niobate (LNO) were prepared via standard hydrothermal and solid–state chemistry reactions, and by the sol–gel method implementing acrylamide polymerization. Congruent LiNbO 3 trigonal perovskite phases crystallized in the R3c (161) space group [ 3 m (C 3v) polar point group] were obtained in all cases. Depending on the implemented synthetic route, the average grain and crystallite sizes were estimated to 127–895 nm and 35–40 nm, respectively. As prepared LNO powders were embedded in a–SiO 2 mesoporous sonogel networks at different doping rates to conform LiNbO 3 :SiO 2 semicrystalline hybrid silicates with differentiated structural and optoelectronic (OE) properties. Intensive morphological, structural, spectroscopic, and nonlinear optical (NLO) characterizations were performed to explore these novel composites' structural and photophysical properties for lead–free ferroelectric and optical applications. Results show that the massive porosity of the sonogel glasses and related defective bonding environment promote generalized host–guest molecular interactions influencing the oxidation states and radiative transitions of the dopant compounds via surface–assisted mechanisms and chemical charge–transfers. Additionally, due to the ferroelectric nature of LNO and average macroscopic alignment attained along the polycondensation stage of the solid solutions, SHG activity was observed from the hybrid sonogel (HSG) phases. Bulk NLO susceptibilities and molecular hyperpolarizabilities were estimated within the 9.62 × 10−11 and 10−23 esu range, respectively. Finally, depending on the synthesis methodology and in–gap hybridized levels, energy gap (E g) narrowing was also observed for all LNO/HSG glasses, showing E g values as low as 3.05 eV. • Nanometric-sized LiNbO 3 ceramics were synthetized by different chemical routes. • LiNbO 3 crystallites were embedded in porous a - SiO 2 sonogel networks. • Novel semiconducting ferroelectric LiNbO 3 :SiO 2 glassy composites were obtained. • Structural & optical characterizations of the LiNbO 3 :SiO 2 silicates were performed. • NLO/SHG response was detected in bulk semicrystalline hybrid glasses. [ABSTRACT FROM AUTHOR]

We report on the spectroscopic investigation of Er 3+ doped BaF 2 single crystals. High-quality crystals have been gown by the Bridgman-Stockbarger pulling technique. The room temperature absorption, excitation, emission and fluorescence decay spectra of the luminescent Er 3+ ions inserted in BaF 2 fluoride single crystals have been investigated. Using the Judd-Ofelt (JO) theory, the intensity parameters of Er 3+ ions have been calculated to be Ω 2  = 0.949 × 10 −20  cm 2 , Ω 4  = 0.975 × 10 −20  cm 2 and Ω 6  = 1.258 × 10 −20  cm 2 . These parameters were then used to calculate the radiative transition probabilities (A JJ′ ), branching ratios (β JJ′ ) and radiative lifetimes (τ rad ) of the main laser emitting levels of Er 3+ ions. The obtained spectroscopic properties are compared to those of Er 3+ transitions in other fluoride and oxide hosts. The excitation spectrum in the UV–Visible spectral range is very close to the absorption spectrum indicating that all observed absorption levels can excite the Erbium green emission. The emission spectrum is mainly dominated by the green emission alongside a weak red emission. For the main transitions, there is a good agreement between the emission spectrum and the spontaneous emission probabilities given by the JO analysis. Using the Fuchtbauer–Ladenburg method, the emission cross-section of the three main visible emission were determined in addition to other important laser parameters such radiative quantum efficiency and optical gain. [ABSTRACT FROM AUTHOR]

The photoluminescence characteristics of praseodymium (Pr 3+ ) doped zirconia/polyethylene glycol (ZrO 2 /PEG) samples were studied using optical absorption and emission spectra. The optical properties were theoretically analysed using standard and modified Judd-Ofelt (J-O) models. The oscillator strength of the observed transitions and J-O intensity parameters were calculated using these J-O models. The radiative properties such as radiative transition probability ( A T ), branching ratio ( β R ), stimulated emission cross-section ( σ e ) and gain band width ( σ e × Δ λ e f f ) for the excited states of Pr 3+ in ZrO 2 /PEG composite have been determined. The experimental branching ratios obtained from the emission spectra were compared with the theoretical values. The excitation spectra of Pr 3+ doped samples show overlapping of Pr 3+ excitation peak at 448 nm at the end of the broad excitation band of the host, indicating the charge transfer between the host and Pr 3+ ions. Luminescence decay analysis confirmed concentration quenching in the prepared samples and the lifetime values are found to be in the microsecond range. [ABSTRACT FROM AUTHOR]

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]

In this paper, structural and optical properties of WO 2.72 thin films implanted by 150 keV Ni ions having ion fluences in the range of 1015 to 1016 ions/cm2 have been investigated. Structural investigations (Raman and XRD) suggest the formation of the crystalline monoclinic phase of pristine films. However, after ion implantation, the crystalline quality degrades as a function of ion fluences, and complete amorphization is observed at highest fluence. Further, the bandgap decreases upon ion implantation as a result of band tailing effect. Optical investigation under UV excitation delineates the existence of NUV, band-to-band transition and blue green emission bands in WO 2.72 thin films. Implantation-assisted Ni doping blueshifted the new NUV emission peaks due to the enhancement in free electron concentration in the conduction band (CB). The overall hue of the emitted light investigated using Commission International de l'Eclairage (CIE) diagram demonstrates the transition from light to deep blue region upon Ni implantation. • Structural and optical properties of WO 2.72 thin films implanted with Ni ions were studied. • Amorphous films are obtained at high Ni fluences. • Multiple radiative transitions due to intrinsic and implantation induced defects were obtained. • Implantation-assisted doping of Ni leads to the production of oxygen vacancies. • The CIE coordinates depicts the tuning of color from light blue to deep blue. [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]

Sr 3−2 x Sm x Na x B 2 SiO 8 phosphors were synthesized by the solid-state reactions. X-ray diffraction, diffuse reflection, photoluminescence excitation and emission, as well as fluorescence decay measurements were utilized to investigate the structural and spectral properties of the samples. The results indicated that Sr 3−2 x Sm x Na x B 2 SiO 8 phosphors could be efficiently excited by the near-ultraviolet light to realize a novel reddish orange luminescence corresponding to the characteristic transitions 4 G 5/2 → 6 H J (J = 5/2, 7/2, 9/2, 11/2) of Sm 3+ ions, with a maximum intensity at 600 nm. Based on the theoretical calculation, the dipole–dipole interaction was dominantly involved concentration quenching of Sm 3+ in the phosphors, and the critical transfer distance ( R c ) was determined to be 13.59 Å. Furthermore, Judd-Ofelt analysis was applied to evaluate three phenomenological Judd-Ofelt intensity parameters ( Ω λ , λ = 2, 4, 6), and in turn radiative properties such as radiative transition probabilities ( A R ), radiative lifetimes ( τ R ) and fluorescence branching ratios ( β R ) for the excited 4 G 5/2 luminescent level of Sm 3+ ions were determined. Upon 402 nm excitation, the composition-optimized Sr 2.90 Sm 0.05 Na 0.05 B 2 SiO 8 exhibited the preferable photoluminescence intensity and CIE coordinates of (0.534, 0.448). These results suggest that the Sm 3+ -doped Sr 3 B 2 SiO 8 phosphors are competitive as the reddish orange-emitting phosphor-converted materials for application in near-ultraviolet-pumped LEDs. [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]

Alkaline earth titanium borate glasses doped with different ratios of Er3+ ions were fabricated using standard melt quenching technique. The density of the glasses increased from 3.652 to 3.762 g/cm3 as the ratio of Er3+ ions increased from 0 to 5.640 × 1020 cm−3. The gaussian deconvolution of the Raman and FTIR spectra was investigated, and the distinctive spectral vibrational bands were assigned. The UV–Vis–NIR absorption spectra of the erbium doped glasses exhibit nine bands located at 1531, 980, 808, 654, 520, 490, 446, 408, and 377 nm due to the electronic transitions of Er3+ ions from the ground level 4I 15/2 to the higher excited levels 4I 13/2 , 4I 11/2 , 4I 9/2 , 4F 9/2 , 2H 11/2 , 4F 7/2 , 4F 3/2 , 2G 9/2 , and 4G 11/2 , respectively. The structural and luminescent properties of the erbium doped glasses were investigated by calculating Judd – Ofelt intensity parameters, radiative transition probabilities, branching ratio, lifetime, full width at half maximum (FWHM), and gain bandwidth (FWHM × σ emis). The intensity parameters followed the trend as Ω 2 > Ω 6 > Ω 4 for all glasses. The values of Ω 2 decreased from 5.2079 × 10−20 to 3.8133 × 10−20 cm2 and that of Ω 4 decreased from 0.7402 × 10−20 to 0.5939 × 10−20 cm2 as the ratio of Er3+ ions increased. The high laser efficiency of the studied glasses were verified by the high values of the radiative lifetime, branching ratio, FWHM, and gain bandwidth. The gain spectra for BaTiBEr3 and BaTiBEr5 glasses covered the conventional (1530–1565 nm) and long (1565–1625 nm) communication bands. Moreover, the high values of the FWHM and gain bandwidth for BaTiBEr3 and BaTiBEr5 glasses, suggested their suitability for photonic applications in the near infrared region and broadband optical fiber amplifiers. • Er3+- doped alkaline earth titanium borate glasses are fabricated via standard melt quenching technique. • Gaussian deconvolution of Raman and FTIR spectra is investigated, and distinctive vibrational bands are assigned. • Radiative properties of 4f – 4f electronic transitions were investigated through Judd – Ofelt theory and PL spectroscopy. • The gain spectra for BaTiBEr3 and BaTiBEr5 glasses cover the conventional and long communication bands. • BaTiBEr3 and BaTiBEr5 glasses have the potential to design erbium doped fiber amplifiers for networking applications. [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]

Judd–Ofelt (J–O) theory has been applied to a series of LiLa 1− x Eu x (PO 3 ) 4 ( x = 5%; 10%; 15%; 20% and 30%) polycrystalline powders based on their emission spectra. J–O intensity parameters Ω λ ( λ = 2, 4) and various radiative properties such as the radiative transition probability ( A ), radiative life time ( τ R ), branching ratio ( β R ) and stimulated emission cross-section ( σ e ) have been determined. The observed trend for J–O parameters ( Ω 2 < Ω 4 ) reveals the ionic character of La(Eu)–O bond as well as the symmetry environment around the Eu 3+ ion in LiLa(PO 3 ) 4 . The experimental decay curves of the 5 D 0 level in LiLa 1− x Eu x (PO 3 ) 4 have a single exponential profile. The registered long life time, low multiphonon relaxation rates ( W NR ), high quantum efficiency ( η ) and the best optical gain parameter ( σ e x τ exp ) have been discussed as function of Eu 3+ concentration, chemical composition and crystal structure of the host matrix and particle-size distribution. A comparative study reveals that LiLa 1− x Eu x (PO 3 ) 4 is promising for use in optical devices as well as for developing visible red lasers to emit at 613 nm. The optical band gap energies of LiLa 1− x Eu x (PO 3 ) 4 have been calculated from the diffuse reflection spectral measurements. The results were discussed as a function of Eu 3+ concentration and compared to reported theoretical results. [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]

The photoluminescence and scintillation properties of Sn2+-doped gadolinium aluminum-silicate Gd 2 O 3 –Al 2 O 3 –SiO 2 (GAS) glasses with Si 3 N 4 as reducing agent were investigated. The glasses showed a wide emission band in the range of 360–730 nm due to the relaxation of S 1 –S 0 and T 1 -S 0 of Sn2+ luminescent centers. The luminescent intensity of Sn2+-doped GAS glasses reaches maximum at 0.3 mol% Sn2+. The lifetimes of the glasses vary between 6 and 12 μs, which related to the full width at half maximum (FWHM) of the emission spectra. Different oxides were added to explore the relationship between optical basicity and the luminescent properties of glasses. The addition of B 2 O 3 increases the photoluminescence quantum yield (PL QY) of the glasses, which is due to reduction of the Stokes shift and increment of radiative transition probability in energy level transition. The X-ray induced scintillation luminescence of the glasses were observed and studied. • The relationship between Stokes shift and optical basicity of the aluminum-silicate glasses. • High photoluminescence quantum yield (PL QY) in the Sn-doped glasses. • Quantitative analysis of the effect of phonon-electron interaction during Sn2+ luminescence. • The luminescence of Sn2+ centers excited by X-ray was observed for the first time in aluminum-silicate glasses. [ABSTRACT FROM AUTHOR]

The aramid-film containing benzimidazole units was synthesized, and its pH sensitive fluorescence enhancement effect was investigated. After surface-treated by acidic ethanol solution (pH 1), the aramid film exhibits noticeable emissive enhancement as high as 33 times than the blank sample. The fluorescence lifetimes of aramid films increase significantly from 0.9 × 10−10 s to 8.2 × 10−10 s. The driving force is ascribed to the decrease of nonradiative transition probability, which comes from the strengthening molecular rigidity of phenyl benzimidazole chromophore within the polymer chains, induced by hydrogen bonds between N-H in benzimidazole group and C=O in amide group. The hydrogen-bond effect is thoroughly proved through examining the repeating molecular units of the aramid polymer chains by the methods of XRD, UV–vis, photoluminescence, molecular simulation, SEM and etc. This pH sensitive fluorescence change should have great potential in the sensor-device design of NH 3 , heavy metal ions or other systems due to the subsequent fluorescence quench effect, because of the excellent mechanical and processability of aramid polymers. Due to the intensified molecular interaction caused by intermolecular hydrogen bonds, benzimidazole based aramid film is pH sensitive in fluorescence enhancement, which is a new finding with great potential in the sensor- or electronic device design of NH 3 , heavy metal ions or other systems based on the subsequent fluorescence quench effect for benzimidazole aramid PBIA film. [Display omitted] • Benzimidazole based aramid film is pH sensitive and fluorescence enhanced 33 times higher after HCl acid-ethanol treatment. • The fluorescence increase is caused by hydrogen bonds induced molecular interaction and radiative transition probability. • The hydrogen bonds are located between N-H in benzimidazole group and C=O in amide group of the chromophore. • This pH sensitive film should have great potential in sensors or electronics with the subsequent fluorescence quench. [ABSTRACT FROM AUTHOR]

Abstract: The work is aimed to research of CsI:Eu single crystals’ luminescence at different excitations in the wide temperature range (from 8 to 300K) and admixture concentration from 10−4% up to 10−1% of Eu2+ ions. This study was directed to separation of different luminescence mechanisms and luminescence quenching explore. It is found that due to the temperature quenching the room temperature yield is decreased in order of magnitude even for heavy Eu doped CsI crystals. Intense low temperature luminescence band at 441–448nm connected with Eu2+ 4f 6 5d →4f 7 radiative transition is observed. The results obtained show that the excitonic mechanism plays the main role in energy transfer process to Eu2+ ions and this is the reason for relatively low light yield of this emission at RT. The nature of the additional emission bands (410, 450, 480 and 500nm) are apparently caused by the significant non-isomorphism of cations and/or by the presence of oxygen-containing admixtures. [Copyright &y& Elsevier]

Abstract: Optical absorption spectra, emission spectra, and fluorescence lifetimes were measured for a number of visible and infrared transitions in Ho3+ doped KPb2Cl5. Judd–Ofelt parameters were obtained by using the conventional approach, as well as by a modified approach that minimizes the fractional difference, rather than the absolute difference, between calculated and measured oscillator strengths. Both procedures gave good overall agreement between measured and calculated lifetimes, with an average difference of ≈15%. This confirms the expectation from the multiphonon energy gap law that most observed transitions in Ho3+:KPb2Cl5 are highly radiative. Emission cross section spectra for the transitions 5F3 → 5I8, 5G5 → 5I7, 5F3 → 5I7, 5F4/5S2 → 5I7, and 5I7 → 5I8 were obtained from measured emission spectra, with the peak cross section values scaled by the Judd–Ofelt calculated oscillator strengths. [Copyright &y& Elsevier]

Abstract: Glasses having compositions 20CdO⋅xBi2O3⋅(79.5− x)B2O3 (15⩽ x ⩽35) doped with 0.5mol% of Sm3+ and Nd3+ ions were prepared by melt quench technique. The amorphous nature of the glasses was confirmed by X-ray diffraction studies. The spectroscopic properties of the glasses were investigated using optical absorption and fluorescence spectra. The structural investigations of these glasses were carried out by recording the Fourier transform infrared spectra. The Judd–Ofelt intensity parameters Ωλ (λ =2, 4, 6) and other radiative properties like radiative transition probability, radiative life time, branching ratio and stimulated emission cross-section of the prepared glasses have been calculated. The variation of Ω 2 with Bi2O3 content has been attributed to changes in the asymmetry of the ligand field at the rare earth ion site and to the changes in their rare earth oxygen (RE-O) covalency. The shift in the hypersensitive band shows that the covalency of the RE-O bond increases with increase of Bi2O3 content, and it is attributed to the increased interaction between the rare earth ions and the non-bridging oxygens (NBO’s). The radiative transition probabilities of the rare earth ions are large in cadmium bismuth borate glasses, suggesting their suitability as a potential candidate for laser application. Further, the FTIR results reveal that the glasses have BO3, BO4 and non-bridging oxygen as local structure. [Copyright &y& Elsevier]

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: The photoluminescence and excitation spectra of Pr3+ activated LaPO4 has been investigated in the 1.6–300K temperature region. At room temperature, the luminescence of LaPO4:Pr3+ is composed of the interconfigurational 4f15d1 →4f2 emission transitions. However, in the 1.6–60K temperature range, the emission spectrum also consists of the intraconfigurational emission transitions that emanate from the 1S0 state. A radiative lifetime of 145ns is measured for the Pr3+ 1S0 → 1I6 emission transition in LaPO4. This is one of the shortest radiative lifetime observed for this transition in a solid. The energy position of the Pr3+ 1S0 state in LaPO4 is established by high-resolution emission spectrum at 46 375±5cm−1. A detailed analysis of the thermal quenching of the 1S0 lifetime and emission intensity is presented. It is proposed that the lowest energy state of the relaxed 4f15d1 configuration is situated energetically below that of the 1S0 state. [ABSTRACT FROM AUTHOR]

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: The temperature dependence of the spectral positions and widths of the photoluminescence lines corresponding to the 5D0 → 7F0, 5D0 → 7F1 and 5D1 → 7F0 electronic transitions in Sm2+-doped SrFCl crystal was measured between 87 and 625K at ambient pressure. The temperature dependence of the homogeneous line width Γh (T) for all these transitions in the whole temperature range used can be described by the two-phonon Raman scattering of acoustic phonons with the Debye temperature TD ≈230K. Comparison of the temperature- and pressure-induced shifts revealed why all the emission lines studied show the blue temperature shifts. It is so because a greater part of the line shift is caused by the thermal expansion of the host crystal and not by enhancement of the electron–phonon coupling with increasing temperature. [ABSTRACT FROM AUTHOR]

Abstract: Here we present the results of our theoretical study of the optical characteristics (lifetimes, IR absorption coefficient, Raman gain coefficient) for small-radius optical centers in subwavelength spherical and ellipsoidal nanocrystals embedded in a dielectric medium. [ABSTRACT FROM AUTHOR]

Abstract: Spectroscopic characterization for optical amplification and laser application of the Er3+-doped Bi4Si3O12 glass is performed through its absorption and luminescence spectra. The spontaneous radiative transition probabilities from the first seven excited states to the ending states are calculated to obtain the luminescence branching ratios and radiative lifetimes. Intense infrared to visible luminescence of the Er3+ ion is observed with 4I9/2 state excitation (800nm) under a 200mW laser excitation power. The value obtained for the ratio of the 4I11/2 → 4F7/2 excited-state absorption oscillator strength to the 4I15/2 → 4I11/2 ground state absorption oscillator strength is in accordance with those reported for Er3+-doped materials pumped efficiently at 4I11/2 level excitation wavelengths. Gain cross-section spectra as a function of the inverted population rate and the stimulated emission cross-section spectrum were determined for the 4I13/2 → 4I15/2 infrared (IR) laser transition. The large gain bandwidth of the 4I13/2 → 4I15/2 IR emission has resulted in being close to those reported for Er3+-doped oxide glasses suitable for broadband amplifiers. [Copyright &y& Elsevier]

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]

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: 53.3BiO1.5–33.3GeO2–13.4NaO0.5 (cation%) glasses with various Tm3+ concentration were prepared by melt-quenching method. These glasses show high density, high refractive index, low phonon energy and good stability against crystallization. Absorption spectra of Tm3+-doped bismuthate glass were measured to obtain the radiative lifetimes by Judd-Ofelt theory. The absorption (4.5×10−21 cm2) and emission (6.7×10−21 cm2) cross-sections were calculated by Beer–Lambert and McCumber theory. The results show that the Tm3+ (3F4 → 3H6) in these glasses have high spontaneous radiative transition probabilities and large stimulated emission cross-section. Then the fluorescence emission spectra were measured under 808nm excitation and the maximum emission intensity at 1.8μm is obtained at 0.9mol% Tm2O3 in the glasses. [Copyright &y& Elsevier]

Abstract: Optical absorption and emission spectra of Ho3+ doped alkali, mixed alkali and calcium phosphate glasses of the type (69.5NH4H2PO4·15Na2HPO4)·15R2CO3 (R=Li, Na and K), (69.5NH4H2PO4·15Na2HPO4)·7.5Li2CO3·7.5R2CO3 (R=Na and K), (69.5NH4H2PO4·15Na2HPO4)·7.5Na2CO3·7.5K2CO3 and (69.5NH4H2PO4·15Na2HPO4)·15CaCO3 have been studied. Variation of Judd–Ofelt intensity of parameters (Ωλ ), peak wavelengths of the hypersensitive transitions (λp ), radiative transition probabilities (A rad) and peak emission cross-sections (σp ) with the variation of alkalis, mixed alkalis and calcium in the phosphate glass matrix has been studied. The shift in peak wavelength of the hypersensitive transition and Judd–Ofelt intensity parameter (Ω 2) are correlated with the structural changes in the host matrix. Radiative lifetimes (τR ) are estimated for certain excited states of Ho3+ in these glass matrices. From the luminescence spectra, the emission cross-sections (σp ) are evaluated for the two emission transitions of Ho3+ ion. Variation of luminescence intensities of the two transitions, absorption and emission cross-sections with the variation of alkalies, mixed alkalies and calcium in the above phosphate glass systems has been studied. [Copyright &y& Elsevier]

Abstract: Evidence of a positive optical gain has been observed in an Er3+-doped LuVO4 crystal in a pump and probe experiment. The radiative transition from the 4S3/2(2H11/2) level to the 4I13/2 metastable level of the Er3+ ion gives rise to an intense emission centred at 850nm. The 4S3/2(2H11/2) level of Er3+ ions is populated with high power laser pulses at 532nm due to the 4I15/2 → 4S3/2(2H11/2) ground state absorption. The 4S3/2(2H11/2)→ 4I13/2 electronic transition is stimulated with a low signal cw beam at 850nm. Under these conditions, the high power pump pulses allowed to reach the population inversion necessary between the Er3+ levels of the transition 4S3/2(2H11/2)→ 4I13/2. An increase of the emission intensity of the sample is observed at the signal wavelength, due to the stimulated emission. Positive optical gain around 2cm−1 (8.6dB/cm) has been measured in Er3+-doped LuVO4 crystal. [Copyright &y& Elsevier]

Abstract: Tm3+ and Ho3+ co-doped TeO2–ZnO–Bi2O3 (TZB) glasses were prepared by the conventional melt-quenching method. Two micrometre emission properties of the TZB glasses exited by 808nm Laser Diode (LD) were analyzed and discussed. The Judd–Ofelt parameters, spontaneous radiative transition probabilities and radiative lifetime of Ho3+ were calculated based on the absorption spectra by using Judd–Ofelt theory. The absorption spectra and fluorescence spectra were measured. The predicted spontaneous radiative transition rate of 5I7 → 5I8 of Ho3+ is as high as 466.8 s−1. The result of fluorescence spectra indicates that the maximum emission intensity of Ho3+ 2.0μm and of Tm3+ 1.47μm emission can be achieved at the concentration of 1mol% Tm2O3 and 1mol% Ho2O3 in TZB glasses. The maximum absorption and emission cross-section of Ho3+ near 2.0μm are 0.87×10−20 cm2 at 1951nm and 1.07×10−20 cm2 at 2047nm, respectively. [Copyright &y& Elsevier]

Abstract: Glasses having composition 20ZnO·xBi2O3·(79− x)B2O3 (15⩽ x ⩽35mol%) and doped with 1mol% Sm3+ ions have been prepared by melt quench technique. Optical absorption and fluorescence spectra have been recorded. Judd–Ofelt approach has been applied for the f ↔ f transition of Sm3+ ions to evaluate various intensity parameters (Ω 2, Ω 4, Ω 6). The variations in intensity parameters, radiative transition probabilities and hypersensitive band positions with composition have been discussed. The variation of Ω 2 with Bi2O3 content have been attributed to change in the asymmetry of the ligand field at the rare earth ion site and to the changes in their rare earth–oxygen (RE–O) covalency, whereas the variation of Ω 6 is found to be strongly dependent on nephlauxetic effect. The shift of the hypersensitive band shows that the covalency of the RE–O bond increases with increase of Bi2O3 content due to increased interaction between the Sm3+ ion and non-bridging oxygens. The radiative transition probabilities for the Sm3+ ions are large in zinc bismuth borate glasses, suggesting their suitability as laser material. [Copyright &y& Elsevier]

Abstract: Interconfigurational 4f 105d ↔4f 11 transitions of the Er3+ ion in the YAG host were studied under both VUV photon (synchrotron radiation) and electron beam excitation. It was found that the lowest low-spin 5d level of the Er3+ ion has a rather large energy gap to the next lower 4f 2 D(2)5/2 crystal-field level, which results in a relatively low rate of nonradiative transitions from this 5d level leading to the appearance of weak spin-allowed 5d–4f luminescence at low temperature. The lowest high-spin 5d level, from which spin-forbidden 5d–4f radiative transitions could occur potentially, is situated only at ∼500cm−1 above the 4 D 1/2 level. Such close location allows fast depopulation of the 5d level resulting in the absence of spin-forbidden 5d–4f luminescence and appearance of 4 D 1/2 4f–4f luminescence. [Copyright &y& Elsevier]

Abstract: Optical absorption and fluorescence spectra of Ho3+ in the geometrically frustrated pyrochlore Ho2Ti2O7 have been measured in the 27,000–4000cm−1 spectral and 295–8K temperature range. The energy positions of the Stark levels have been deduced. The Judd–Ofelt analysis has been performed by fitting the room temperature absorption spectra, and the calculated Judd–Ofelt parameters have been used to evaluate the Ho3+ radiative transition probabilities and the branching ratio. The obtained results show that although the lowest crystal field levels of Ho3+ in Ho2Ti2O7 are well separated, this separation (104cm−1) is smaller than that previously suggested on the basis of neutron and magnetic studies (150–166cm−1). [Copyright &y& Elsevier]

Abstract: From radiative transitions rates in praseodymium, neodymium, erbium, holmium and thulium ions doped LaAlO3 and measured emission decay times multiphonon nonradiative transitions rates W MNR have been calculated. Radiative transition rates were determined in the frame of Judd–Ofelt theory. The data obtained were plotted in the function of energy gap ΔE and fitted by exponential function W MNR =B·exp(−α ·ΔE), where B =1.02×109 and α =3.61×10−3. Fitting results show that multiphonon nonradiative transition rates are low comparing to other oxide crystals being similar to those of YAG. [Copyright &y& Elsevier]

This research paper emphasized on application of Judd-Ofelt's (JO) theory for low doped erbium (0.2 mol%) halogeno-antimonate based glasses with molar composition (90 –x) Sb 2 O 3 - x ZnBr 2 - 10 NaCl (where x = 10, 20, 30 and 40 mol%). 80 Sb 2 O 3 – 9.8 ZnBr 2 - 10 NaCl - 0.2 Er 2 O 3 glass sample has low phonon energy and high refractive index is a potential candidate for luminescence applications. Differential scanning calorimetry (DSC) measurements show good the thermal stability of the prepared glass samples and on the other hand density, expansion coefficient and elastic moduli were reported. Judd-Ofelt's (JO) parameter intensities Ω 2 = 3.27 × 10−20 cm2, Ω 4 = 1.24 × 10−20 cm2 and Ω 6 = 1.88 × 10−20 cm2 were found and these were compared with the literature. Radiative parameters such as spontaneous emission rate, branching ratio and lifetime were calculated. We focused on a high branching ratio radiative transitions 2H 11/2 → 4I 15/2 (β = 0.94) and 4F 9/2 → 4I 15/2 (β = 0.901). The overlap between absorption and emission bands is partial and stokes type shifts were presented. The gain curves were determined after calculation of absorption and stimulated emission cross sections. The infrared transmission curve of the glass matrix was marked extrinsic absorption bands SiO and hydroxyl OH possessed high vibration energy played quenching effect for photoluminescence. • SZNE02 novel glass system was developed by the conventional melt quenching method. • Judd-Ofelt's (JO) parameter intensities were compared with the literature. • High branching ratio radiative transitions. • Optical gap energy (E p = 2.95 eV) and refractive index n = 2.25 • Stimulated emission gains as a function of wavelength for different states of population inversion. [ABSTRACT FROM AUTHOR]

Abstract: A new laser crystal Nd3+: (La,Sr)(Al,Ta)O3 (abbreviated as Nd3+:LSAT) has been grown by the conventional Czochralski method. The absorption and luminescence spectra of trivalent neodymium in Nd3+:LSAT crystal were measured at room temperature. The value of absorption and emission cross-section was calculated. The Judd–Ofelt analysis was applied to the crystal to get the phenomenological parameters (Ω i , i =2,4,6), the line strengths, the radiative transition rates, the branching ratios and the radiative lifetime. [Copyright &y& Elsevier]

Abstract: Nd3+-doped NaLa(WO4)2 single crystal with a dimension of ∅20mm×40mm and a good optical quality was grown by Czochralski method. The polarized absorption spectra and emission spectra were measured at room temperature. The absorption cross-section and emission cross-section were presented. The Judd–Ofelt theory, extended to anisotropic system, has been applied to evaluate the intensity parameters Ω t (t =2,4,6), radiative transition rates A, radiative lifetimes τ R and fluorescent branching ratios β. The calculated radiative lifetime was compared with the experiment data for the 4F3/2 emitting level. All spectral features are strongly affected by an inhomogeneous broadening connected with the ‘disordered crystal’ character of the title compound. [Copyright &y& Elsevier]

Abstract: Mid-IR Nd3+ transitions perspective for laser oscillation were analyzed in the CaGa2S4, PbGa2S4, and PbCl2 crystals and compared with low phonon fluoride crystals. Fluorescence kinetics decay of the high-lying 4G7/2 and 4G5/2; 2G7/2 and low-lying 4I J levels and its temperature dependence in the range of 13–295K were measured. For 5μm mid-IR transitions of Nd3+ the radiative relaxation rates are found to be several times higher and multiphonon relaxation (MR) rates are several times lower in lead and calcium thiogallate crystals compared to low phonon fluoride crystals. MR rate dependence on the Nd3+ to the nearest ligand distance R 0 is established experimentally and analyzed in the frame of point-charge model of nonlinear theory of multiphonon relaxation. Mid-IR Nd3+ 4–5.5μm fluorescence spectra of 4I i –4I j transitions perspective for laser oscillation were measured for the first time in the studied crystals. [Copyright &y& Elsevier]