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Nowadays, the application scenarios of rare earth doped luminescent materials tend to be refined and complicated. The optical properties of rare earth doped materials are difficult to precisely control via the traditional design and synthesis methods, namely, changing doping concentration or preparative conditions. The aim of this study is to tune the optical transition properties of Er3+ in tungsto-molybdate NaY(Mo x W 1- x O 4) 2 (x = 0, 0.01, 0.1, 0.3, 0.5, 0.7, 0.9, 0.99 and 1.0) phosphors by changing the host matrix. The Er3+ doped continuous tungsto-molybdate solid solution NaY(Mo x W 1- x O 4) 2 phosphors were prepared via a solid state reaction technique at optimized calcination temperatures. The refractive indexes of the obtained solid solution samples were confirmed according to different models and compared. Subsequently, the optical transition intensity parameters, radiative transition rates and intrinsic radiative lifetimes of Er3+ in these solid solution phosphors were calculated in the framework of Judd-Ofelt theory. It was confirmed that the optical transition properties of Er3+ can be greatly tuned by the solid solution composition, and the tuning effects for different transitions are different. To validate the reliability of the Judd-Ofelt calculations, the temperature-dependent emission spectra of two green emissions of Er3+ for different solid solution samples were studied. It was found that the radiative transition rate ratios between two green emissions derived from theoretical calculations and experimental measurements are in reasonable agreement, thus proving that the optical transition calculations are reliable and the optical transition properties of Er3+ in the tungsto-molybdates can be tuned in a large range. This work reminds us of a new route for developing novel luminescence materials based on practical demands. [ABSTRACT FROM AUTHOR]

Exploiting emissive hydrophobic nanoclusters for hydrophilic applications remains a challenge because of photoluminescence (PL) quenching during phase transfer. In addition, the mechanism underlying PL quenching remains unclear. In this study, the PL‐quenching mechanism was examined by analyzing the atomically precise structures and optical properties of a surface‐engineered Ag29 nanocluster with an all‐around‐carboxyl‐functionalized surface. Specifically, phase‐transfer‐triggered PL quenching was justified as molecular decoupling, which directed an unfixed cluster surface and weakened the radiative transition. Furthermore, emission recovery of the quenched nanoclusters was accomplished by using a supramolecular recoupling approach through the glutathione‐addition‐induced aggregation of cluster molecules, wherein the restriction of intracluster motion and intercluster rotation strengthened the radiative transition of the clusters. The results of this work offer a new perspective on structure‐emission correlations for atomically precise nanoclusters and hopefully provide insight into the fabrication of highly emissive cluster‐based nanomaterials for downstream hydrophilic applications. [ABSTRACT FROM AUTHOR]

Exploiting emissive hydrophobic nanoclusters for hydrophilic applications remains a challenge because of photoluminescence (PL) quenching during phase transfer. In addition, the mechanism underlying PL quenching remains unclear. In this study, the PL‐quenching mechanism was examined by analyzing the atomically precise structures and optical properties of a surface‐engineered Ag29 nanocluster with an all‐around‐carboxyl‐functionalized surface. Specifically, phase‐transfer‐triggered PL quenching was justified as molecular decoupling, which directed an unfixed cluster surface and weakened the radiative transition. Furthermore, emission recovery of the quenched nanoclusters was accomplished by using a supramolecular recoupling approach through the glutathione‐addition‐induced aggregation of cluster molecules, wherein the restriction of intracluster motion and intercluster rotation strengthened the radiative transition of the clusters. The results of this work offer a new perspective on structure‐emission correlations for atomically precise nanoclusters and hopefully provide insight into the fabrication of highly emissive cluster‐based nanomaterials for downstream hydrophilic applications. [ABSTRACT FROM AUTHOR]

As an emerging 2D ultrawide bandgap semiconductor, hexagonal boron nitride (h‐BN) is gaining significant attention for its superior properties and wide applications. Although optical properties of h‐BN have been partially revealed by using h‐BN bulk single crystal, luminescence properties of the h‐BN few‐layer are rare due to its poor crystallinity. In this work, the h‐BN epilayers have been synthesized on sapphire substrates by the submicron‐spacing vapor deposition method. The crystalline quality of the h‐BN epilayer is improved with the increase of the growth temperature, and the full width at half‐maximum of the Raman peak is only ≈13 cm−1. The low temperature cathodoluminescence spectra of h‐BN epilayers exhibit two strong deep ultraviolet (DUV) luminescence peaks at 5.49 and 5.35 eV, as well as a weaker and broader defect‐related emission band at ≈4.0 eV. The DUV emission band is ascribed to the recombination of bound excitons and its phonon replica. Based on the theoretically predicted energy levels, the 4.0 eV emission band is tentatively attributed to the radiative transition from C impurities occupying the B sites to the B vacancies. Moreover, the h‐BN‐based DUV photodetectors exhibit an outstanding performance, making it a promising prospect for optoelectronic applications. [ABSTRACT FROM AUTHOR]

The NaGdF4:Nd3+@Ni core@shell nanoparticles were synthesized and characterized. First, core@shell nanoparticles were synthesized using a solvothermal method to obtain the NaGdF4:Nd3+ core with hexagonal phase; subsequently, a chemical reduction was performed to stimulate the growth of the Ni shell with cubic phase. NaGdF4:Nd3+@Ni nanoparticles were characterized by transmission electron microscope, zeta potential, X-ray diffraction, scattered energy spectroscopy, UV-Vis, and photoluminescence emission spectra. The nanoparticles were round in shape, with mean sizes around 250 nm. The core@shell nanoparticles presented a homogenous composition and good stability. The photoluminescent emission of the nanoparticles was recorded at 1059 nm in the near-infrared spectral range; this band corresponds to the 4F3/2→4I11/2 radiative transitions of Nd3+ ions. The synthesized nanoparticles, being hydrophilic, have potential for use in different areas, one of them could be in anaerobic digestion. [ABSTRACT FROM AUTHOR]

In this study, the optical and structural properties of carbon dots (CDs) synthesized using a hydrothermal method were investigated. CDs were prepared from various precursors such as citric acid (CA), glucose, and birch bark soot. The SEM and AFM results show that the CDs are disc-shaped nanoparticles with dimensions of ~7 nm × 2 nm for CDs from CA, ~11 nm × 4 nm for CDs from glucose, and ~16 nm × 6 nm for CDs from soot. The TEM images of CDs from CA showed stripes with a distance of 0.34 nm between them. We assumed that the CDs synthesized from CA and glucose consisted of graphene nanoplates located perpendicular to the disc plane. The synthesized CDs contain oxygen (hydroxyl, carboxyl, carbonyl) and nitrogen (amino, nitro) functional groups. CDs have strong absorption in the ultraviolet region in the range of 200–300 nm. All CDs synthesized from different precursors displayed bright luminescence in the blue-green region of the spectrum (420–565 nm). We found that the luminescence of CDs depended on the synthesis time and type of precursors. The results show that the radiative transitions of electrons occur from two levels with energies ~3.0 eV and ~2.6 eV, which are due to the presence of functional groups. [ABSTRACT FROM AUTHOR]

Lead‐free double perovskite nanocrystals (NCs) are a promising alternative to lead‐based perovskite NCs for optoelectronic materials due to their nontoxic and good moist‐thermal stability. However, most of the lead‐free double perovskite NCs exhibit unsatisfying photoluminescence quantum yield (PLQY); the metal ions doping is an effective method to improve the optical properties. Here, monodisperse, homogeneous cubic morphology of Na+‐doped Cs2AgBiBr6 NCs is prepared via a colloidal synthesis strategy. When Na+ is doped into Cs2AgBiBr6 NCs, the inversion‐symmetry‐induced parity‐forbidden transition is broken. So, the wave function parity of the self‐trapped excitons at Ag atoms is changed, which allows the radiative transition to occur. This leads to a higher PLQY for Na+‐doped Cs2AgBiBr6 NCs (9.08%) than that for Cs2AgBiBr6 NCs (0.40%), and the exciton lifetime is extended from 1.87 ns for Cs2AgBiBr6 NCs to 17.15 ns for Na+‐doped Cs2AgBiBr6 NCs. The Na+ doping elevates the longitudinal optical phonon energy and exciton binding energy, which results in weaker nonradiative transitions during exciton recombination and improved NC thermal stability. So, the Na+‐doped Cs2AgBiBr6 NCs maybe possess potentially valuable applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

We design thermal emitters based on gold micrograting structures with VO2-filled slots for enhanced far-field thermal rectification. We numerically calculate the thermal rectification ratio for two different approaches, peak extinction and peak shift. In peak extinction, the VO2 phase transition switches the radiative coupling of the surface plasmon on and off. In peak shift, the phase transition shifts the wavelength of the radiatively-coupled surface plasmon. We vary the extinction coefficient of VO2 to determine the effect on rectification for each approach. In both cases, the rectification ratio can be increased by increasing the VO2 loss in the metallic state. This suggests that highly efficient, microstructured thermal rectifiers can be achieved via suitable manipulation of the optical properties of VO2. [ABSTRACT FROM AUTHOR]

Two new heteroleptic cationic Ir(III) complexes bearing benzothiazole and pyridine motifs on fluorene groups were synthesized and characterized. Complexes Ir1 and Ir2 exhibit 1π,π* transitions below 430 nm, with broad but weak metal-to-ligand and ligand-to-ligand charge transfer absorption bands above 430 nm. Both complexes possess long-lived emissions (τem = 0.37 μs for Ir1, τem = 5.41 μs for Ir2) and triplet excited states (τTA = 0.14 μs for Ir1, τTA = 6.06 μs for Ir2). Their optical properties in solution and aggregated states were also investigated. Both Ir(III) complexes exhibit aggregation-induced phosphorescence emission behavior in an acetonitrile–water mixture. As the water content increased to 90%, the emission intensities of complexes Ir1 and Ir2 increased nearly 3 times and 2.8 times, respectively. Moreover, nonlinear transmittance experiments were performed in CH3CN and a CH3CN–H2O mixture (fw = 90%), and the strength of the reverse saturable absorption (RSA) at 532 nm followed the trend: Ir2 (CH3CN) ≥ Ir1 (CH3CN) > Ir2 (CH3CN–H2O) > Ir1 (CH3CN–H2O). Abundant triplet state excitons participated in the radiative transition progress, which inhibited the RSA process. These results indicate that the fluorene-decorated Ir(III) complexes are suitable for aggregation emission and optical power limiting applications. [ABSTRACT FROM AUTHOR]

Herein, Mn4+‐doped alkaline‐germanate phosphors are synthesized by using starting chemicals of alkaline (K, Rb) carbonates, GeO2 and MnO2. The compounds exhibit bright red photoluminescence (PL) under ultraviolet and blue excitation. X‐ray diffraction (XRD) and Raman investigation show the formation of solid solutions of trigonal KxRb2−xGe4O9. The potassium content dependence of the red PL shows the intensity maximized at x = 0.5 and 1.5. This behavior is well matched with the absorption of Mn4+ ions. PL quantum efficiencies (QEs) are also estimated and compared with a previous result for germanates synthesized with Mn carbonates as a starting material. The radiative and nonradiative transition probabilities are also estimated to understand the reason for the observed PL properties, revealing the higher nonradiative transition probability resulting from concentration quenching due to the starting chemical of MnO2. Ab initio calculations are also performed on the electronic structure of the host crystals of the end members of the obtained compounds, K2Ge4O9 and Rb2Ge4O9. The optical bandgap calculated varies between K and Rb, while the observed ones are not sensitive to the K content x. Nevertheless, they are high enough for the optimal red emission of Mn4+ ions via an excitation of 4A2g–4T1g or 4T2g. [ABSTRACT FROM AUTHOR]

Optical properties of cesium bismuth germanate Cs 2 Bi 2 O(Ge 2 O 7) (CBGO) nonlinear single crystal doped with trivalent europium (Eu3+) ions grown from melt were investigated. Strong Eu3+ emission lines in the orange-red range centered at 576, 596, and 617 nm originating from the 5D 0 to 7F 0,1,2 transitions, respectively, were observed. Judd-Ofelt intensity parameters describing f-f transitions were calculated from the room temperature emission and excitation spectra and were used to determine spectroscopic parameters such as radiative lifetimes, transition probabilities and branching ratios3 for 5D 0 level of Eu3+. The values obtained by using Judd-Ofelt approach were compared with experimental results for the 5D 0 excited state. The measurement of the 5D 0 fluorescence decay of Eu3+ ions in the Cs 2 Bi 2 O(Ge 2 O 7) matrix (0.5 at.% in the alloy) confirmed its exponential nature, with a time constant of 0.82 ms at 300 K. The high-resolution laser spectroscopy of CBGO Eu3+ performed at 10 K confirmed the Eu3+ distribution into two distinct sites. Based on both the results of optical spectroscopy and structural analysis, the allocation of sites for Eu3+ ions was discussed. • Cs 2 Bi 2 O(Ge 2 O 7):Eu3+ crystals have been grown from stoichiometric melts under conditions of low temperature gradient. • Judd-Ofelt intensity parameters for f-f transitions in CGBO:Eu3+ have been determined. • The Eu3+ distribution into two distinct sites in CBGO host has been experimentally confirmed. • The values of transition probability and radiative lifetime of the 5D 0 level of Eu3+ in CBGO crystal have been determined. [ABSTRACT FROM AUTHOR]

This paper reports the physical, structural, optical and luminescence properties of Er 3 + doped borophosphate glasses. The samples were prepared with melt quenching technique at 1250 ∘ C by varying the concentration of Er 2 O 3 from 0.1 to 0.5 mol%. Density is measured by Archimedes principle and variation in density with erbium's concentration established its participation in the glass structure. X-ray diffraction affirmed the amorphous nature of the prepared glasses. Fourier transform infrared spectroscopy spectra revealed the structural units such as P--O--P , B--O--B and BO 4 present due to stretching and bending vibrations of various bonds. Ultra-violet-visible absorption spectra displayed various absorption peaks/bands originating from ground state of erbium 4 I 15 / 2 to 2 K 15 / 2 , 4 G 9 / 2 , 4 G 11 / 2 , 2 G 9 / 2 , 4 F 5 / 2 , 4 F 7 / 2 , 2 H 11 / 2 , 4 S 3 / 2 and 4 F 9 / 2 . The indirect optical band gap values varied between 2.56 and 3.19 eV. Judd Ofelt parameters ( Ω 2 , Ω 4 , Ω 6 ) were evaluated and they followed Ω 2 > Ω 4 > Ω 6 trend. These parameters helped to calculate radiative transition probability, stimulated emission cross section and gain bandwidth. For luminescence studies, the glass samples were excited at 379 nm and emission occured in the visible region showing peaks at 405 nm, 485 nm and 517 nm. Commission International de I'Eclairage (CIE) coordinates (x and y) were calculated for the glass samples and these coordinates lie in the blue region of CIE chromaticity diagram. [ABSTRACT FROM AUTHOR]

The wide applications of ionizing radiation in various important technologies such as 3D industrial tomography, mammography, and small‐animal micro‐CT with low energy X‐ray have increased the demand for precise radiation measurement. Detection technologies have undergone remarkable progress, but most of them strictly rely on the complicate calibration process, thus remarkably limiting their applications. Here, a nanostructured glass composite system for self‐calibrated radiation dose rate detection (at 40 keV X‐ray) is described. Results show that the in situ precipitation of LiGa5O8 nano‐domains from glass composite results in unique emission centers at ≈496 and ≈718 nm with distinct ionizing radiation response. Subsequently, the radiation level is directly assessed by comparing the radiative transition ratio of these two centers. The nanostructured glass composite can also be constructed into fiber, which exhibits perfect core‐clad configuration and maintains excellent optical activity. The novel principle device with self‐calibrated function is successfully constructed, and the application for online radiation monitoring is demonstrated. The results not only provide an alternative opportunity for developing the next generation of ionizing radiation detection system, but also suggest a powerful pathway for the creation of new optical function through nanocrystallization of glass. [ABSTRACT FROM AUTHOR]

In this study, Ho3+-doped 0.825K0.5Na0.5NbO3-0.175Sr(Yb0.5Nb0.5)O3 luminescence transparent ceramics were prepared via the traditional solid-state sintering method. The structure and optical properties of the ceramics before and after polarization were studied at 40 kV cm−1 for 0.5 h. With the increase of Ho content, the phase structure of the ceramics changed from a pseudo-cubic phase to the tripartite and the orthorhombic phases, and the light transmittance decreased. The ceramics demonstrated an up-conversion luminescence characteristic under the excitation of a 980 nm laser, and the emission wavelengths were 550 and 670 nm. The best up-conversion luminescence performance was obtained when the Ho content was 0.1%. Moreover, the polarization markedly enhanced the luminescence performance of the 0.825K0.5Na0.5NbO3-0.175Sr(Yb0.5Nb0.5)O3-0.1%Ho ceramics due to the increased possibility of energy-level radiative transition of rare-earth Ho3+ ions and reduction of the Eg value of the ceramic. [ABSTRACT FROM AUTHOR]

[Display omitted] • Er3+ doped bismuth flourophosphate glasses were successfully prepared by high temperature melting method. • The influence of modifier cations as ligand field surrounding Er3+ ions on the optical properties was analyzed. • The visible and near-infrared emission of Er3+ doped bismuth flourophopsphate glasses were investigated. • Broadband emissions at visible and near-infrared were observed with the excitation of 379 nm and 980 nm respectively. • Various luminescence properties determined and compared with different compositional incorporation. Bismuth flourophosphate glasses doped with Er3+ ions (0.5 mol %) were synthesized using different modifier fluorides with the aid of melt quenching route. The glass samples were labelled as PBiBa AF T (where AF = Li, Na, Mg, K, Ca and Sr fluorides). The influence of cations of network modifiers on the structure and thereby spectroscopic properties of Er3+ ions was analysed via Powder XRD, FTIR, optical absorption and photoluminescence. Existence of relevant vibrational groups and modifications in structure due to the different admixture modifier cations were recognized via FTIR spectra. The Judd-Ofelt parameters abide by the trend Ω 2 > Ω 6 > Ω 4 in the PBiBa Li T, PBiBa K T, PBiBa Ca Tand PBiBa Sr T glasses whereas the trend was noticed to be Ω 2 > Ω 4 > Ω 6 for PBBi Na T and PBiBa Mg T glasses respectively. The visible emission spectra were recorded by exciting at 379 nm exhibit three emission bands centered at 526 nm, 544 nm and 686 nm. NIR emission spectra were recorded by exciting at 980 nm exhibit broad emission at 1535 nm. Admixture of different cations could exhibit change in luminescence intensity and radiative parameters of the prepared glasses. Spectroscopic parameters such as radiative transition probability (A), branching ratio (β), absorption cross section (∑), effective bandwidth (Δλ eff) and optical band gain (σ e × Δλ eff) are calculated. The mid infrared spectroscopic features were investigated. [ABSTRACT FROM AUTHOR]

2D V-MoS 2 microsheets have excellent photoelectric application performances due to their unique growth arrangement. Here, we have grown 2D V-MoS 2 microsheets by magnetron sputtering and investigated their optical properties by temperature-dependent (T -dependent) photoluminescence (PL) from 7 to 300 K. At 7 K and 300 K, the direct A and B exciton peaks and the indirect (I) exciton peak can be observed with PL broadening from 2D V-MoS 2 microsheets. With the increase of temperature, the A and B exciton peaks have a red-shift, and the full width at half maximum (FWHM) becomes wider, whereas the intensities of the A and B exciton peaks exhibits different behaviors. The intensity of the A exciton peak reduces while the B exciton peak intensity is rising. Moreover, the I exciton peak obtains an obvious split, which is almost independent of temperature. The above phenomena are closely related to the temperature dependence of band structure, exciton transition and radiative recombination processes in 2D V-MoS 2 microsheets. Our results enrich the understanding of exciton dynamics in 2D V-MoS 2 microsheets and provide valuable information for the development of MoS 2 -based optoelectronic devices. [ABSTRACT FROM AUTHOR]

In the presented work, the influence of the quantum well and barrier thicknesses on optical characteristics of InGaAs/AlInAs superlattices was reported. Six different structures of In0.53Ga0.47As/Al0.48In0.52As superlattices lattice-matched to InP were grown by low pressure metal organic vapour phase epitaxy (LP-MOVPE). Optical properties of the obtained structures were examined by means of photoluminescence spectroscopy. This technique allows quick, simple and non-destructive measurements of radiative optical transitions in different semiconductor heterostructures. The analysis of recorded photoluminescence spectra revealed the influence of the quantum well and barrier thicknesses on the emission line energy. [ABSTRACT FROM AUTHOR]

Tuning the enhanced optical and magnetic properties of rare earth doped glasses by embedding nanoparticles is a never-ending quest. Influences of heat treatment (annealing) in modifying the spectral features of melt-quench synthesized manganese oxide nanoparticles (Mn 3 O 4 NPs) embedded Eu3+-doped borotellurite glasses are reported. The growth of NPs is tuned by varying the annealing time. TEM micrograph reveals the nucleation of heat treated Mn 3 O 4 NPs and SAED manifest their growth along the (1 1 2) crystallographic planes having average size in the range of 5.2 to 21.4 nm. The SPR bands are evidenced in the range 350 to 700 nm that validates the growth of Mn 3 O 4 NPs in the glass matrix. The luminescence spectra reveal four major emission peaks at 591, 614, 651 and 700 nm originating from 7F 1 , 7F 2 7F 3 , and 7F 4 transitions levels, respectively. Intensity enhancement displayed by heat treated glass samples is attributed to the local field effect of Mn 3 O 4 NPs while a quenching is due to the energy transfer from Eu3+ to Mn 3 O 4 NPs. The intensity parameters related to the radiative transitions within 4f configuration of Eu3+ ions are determined and analyzed using Judd-Ofelt theory. The magnetization versus field (M-H) at 12 h of Mn 3 O 4 NPs shows the highest saturation magnetization. The ESR spectrum exhibits resonance signals with effective isotropic g values at 1.9, 3.0 and 4.3 where g at 1.9 are attributed to Mn2+ centers in an octahedral asymmetry and g at 3.0 and 4.3 are attributed to the rhombic symmetry of the Mn2+ ions. Present glass compositions are established to be promising for the development of photonic devices. • Annealing time dependent optical and magnetic properties of melt quenching synthesized Eu3+ doped BT glasses containing Mn 3 O 4 NPs are reported. • The TEM result without and with annealed reveals the size of NPs while its planar spacing are determined by HRTEM. • The spectroscopic properties of the proposed glasses are determined. • J-O intensity parameters and radiative lifetimes, stimulated emission cross-section and quantum efficiencies are evaluated. • The magnetization measurement of glass sample is carried out using VSM and ESR. [ABSTRACT FROM AUTHOR]

Undoped ZnS and Sm3+ doped with varying concentration of ZnS phosphor materials were synthesized via low temperature solid state reaction method. The samples were investigated for the influence of different concentrations of Sm3+ ions on their structural and spectroscopic properties. The presence of various absorption bands in UV–Vis–NIR spectra revealed the transition from ground state to different excited states of Sm3+ ions. The Judd-Ofelt (JO) analyses were evaluated to identify the structure and the bonding around the Sm3+ ions. The high value of Ω 2 intensity parameter reveals that the site symmetry is lower. The parameters such as radiative transition probabilities, radiative lifetime, branching ratio, stimulated emission cross-sections and the optical gain parameters are also evaluated. The PL spectra shows five high intensity emission bands centered at 567 nm, 590 nm, 619 nm, 641 nm and 667 nm corresponding to 4G 5/2 →6Hj (j = 5/2, 7/2,9/2, 11/2, 13/2) transitions and showed optimum for concentration at x = 0.03 in Zn (1- x) S. The quantum yield of the prepared optimal phosphor using integrating sphere method was found to be 10.08%. This indicates that the materials synthesized may be favorable for the applications of laser and other optical devices. • Hexagonal structured undoped and Sm3+ doped ZnS phosphor were prepared. • The positive value of bonding parameter reveals its covalent nature. • Judd-Ofelt analysis were performed and trend observed is Ω 2 >Ω 4 >Ω 6. • x = 0.03 in Zn (1-x) Sm x S show maximum emission with life time 1.661 ms. • The prepared phosphor could be an excellent candidate for photonic displays. [ABSTRACT FROM AUTHOR]

Powders of ZnO and ZnO:M (M = Al3+ and Sr2+) with 1 and 4% of M nominal content were synthetized by a hydrothermal method in a diethanolamine (DEA) medium. The samples were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), micro-Raman and photoluminescence (PL). The powder particles were spherical with average radius decreasing from 1 μm down to 70 nm with increasing Al3+ nominal content but nearly independent on the Sr2+ nominal content. The XRD and micro-Raman results indicate that both Al3+ and Sr2+ mostly incorporated substitutionally into the ZnO lattice, giving rise to compressive and tensile strain, respectively, as a result of ionic radii differences. The PL spectra for ZnO:Al exhibit a dopant-induced contribution at ∼3.1 eV, which is not observed for ZnO:Sr, due to radiative transitions involving trapping of photocarriers at theoretically expected substitutional Al3+ donor states or at Zn interstitial defects. • ZnO and ZnO:M (M = Al3+ and Sr2+) powders were synthetized by a hydrothermal method • The particles radius decreased from 1 μm down to 70 nm with Al dopant incorporation • Both Al3+ and Sr2+ are mainly incorporated substitutionally • Al3+ and Sr2+ additions to ZnO induce compressive and tensile strain respectively • Al3+ incorporation induced a PL component at ∼3.1 eV related with Zn interstitial [ABSTRACT FROM AUTHOR]

Abstract Nd3+-doped mixed-anion fluoro-sulfo-phosphate (FPS) glass has been investigated as a laser material in detail. It is found that anion-mixing in Al(PO 3) 3 -BaF 2 -BaSO 4 glass system enables excellent physical properties and chemical durability. Besides, the complicated local environment provided by multi-component leads to high radiative transition probability and influences other luminescent properties considerably. The measured lifetime of Nd3+: 4F 3/2 in FPS is 349.8 μs and the quantum efficiency is 92.91%, higher than those of phosphate and fluoro-phosphate glasses. These results suggest that the FPS glass system could be a promising candidate for 1.06 μm laser source. Highlights • Nd3+-doped fluoro-sulfo-phosphate glass systems were investigated. • Glass-forming regions of the glasses were predicted via the thermodynamic method. • Optical and spectroscopic properties of the FPS glass were investigated. [ABSTRACT FROM AUTHOR]

Abstract Sm3+-doped zinc magnesium sulfophosphate glasses were synthesized by conventional melt-quench technique. FTIR spectra were recorded to investigate the structural properties of the glasses. Differential thermal analysis (DTA) was confirmed the thermal stability of studied glass samples. UV–Vis-NIR absorption spectroscopy was obtained and J-O analysis was determined to derive the spectroscopic properties of Sm3+ doped zinc magnesium sulfophosphate glasses. Spontaneous radiative transition probabilities (A), radiative lifetimes (τ R), branching ratios (β) for the excited 4G 5/2 transition level were calculated and discussed. Thirteen absorption peaks were exhibited in the UV–Vis-NIR spectra. Emission spectra exhibited four significant peaks located at 561, 596, 643 and 703 nm which are assigned to the 4G 5/2 →6H 5/2 , 4G 5/2 →6H 7/2 , 4G 5/2 →6H 9/2 and 4G 5/2 →6H 11/2 transitions, respectively and the intensities of all bands were quenched by addition of ZnSO 4 ions contents. The results revealed that the PMS-ZS10 glass matrix has the higher values of branching ratios and emission cross-sections for 4G 5/2 →6H 7/2 transition. It is observed that the Sm3+-doped zinc magnesium sulfophosphate glass can be promise candidate for lasers in the visible range. [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]

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]

Neodymium doped phosphate based glasses with composition of (P 2 O 5 + K 2 O + Al 2 O 3 + CaF 2 ) were prepared. The samples were analysed through differential thermal analysis (DTA), Fourier transform infrared (FTIR), absorption, emission and decay measurements. Judd-Ofelt parameters (Ω λ ) have been determined from the spectral intensities of absorption bands in order to calculate the radiative parameters like radiative transition probabilities (A R ), radiative lifetime (τ R ) and branching ratios (β R ) for the 4 F 3/2 → 4 I 11/2 laser transition of Nd 3 + ion. The effective emission bandwidths (Δλ eff ), experimental branching ratios (β exp ) and stimulated emission cross-sections (σ e ) have been determined from the emission spectrum. The decay curves of the 4 F 3/2 level exhibited almost single exponential nature for all the Nd 3 + ion concentrations. [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]

In recent years, AIE (aggregation-induced emission) fluorophores have attracted great interest owing to their advantages in wide areas and many AIE fluorophores have be designed by combing conventional fluorophores with AIEgens that exhibiting AIE attributes. However, only few efficient AIEgens were developed. Here, novel dihydrobenzoquinolines (h-DHBQs 4a − e and f-DHBQ 5a), a new kind of AIEgens with strong AIE, are reported. DHBQs were synthesized by a catalyst-free multi-component reaction (MCR) in good overall yield and their optical properties were investigated through steady-state and transient fluorescence spectra, single-crystal diffraction, calculated HOMOs and LUMOs. It was found that DHBQs have these characteristics: a) strong AIE, that is, their fluorescence quantum yields lower than 4.1% in solutions, but high to 90.5% in crystals; b) efficient through-bond and -space conjugated nonaromatic central heterocycle; c) radiative-process-favored but non-radiative-decay-prevented self-assemblies; d) emissive excimers; and e) easily tunable fluorescence color. This work affords a new kind of AIEgens with excellent optical properties in solids and a strategy to develop AIEgens by constructing nonaromatic heterocycle using simple MCRs. Novel through-bond and -space conjugated dihydrobenzo[h]/[f]quinolines (h-DHBQs 4a − e and f-DHBQ 5a) can be synthesized by a catalyst-free multicomponent reaction (MCR) in good overall yields. Their fluorescence quantum yields are lower than 4.1% in solutions, but high to 90.5% in crystals because their self-assemblies promote radiative transition but prevent nonradiative transition. Unusually, intermolecular compact π–π stacking causes no conventional emission-quenching. [Display omitted] • Novel dihydrobenzoquinolines could be synthesized by a multicomponent reaction. • They show strong AIE with fluorescence quantum yields as high as 90.5% in crystals. • They have efficient through-space conjugated nonaromatic central heterocycles. • Their self-assemblies favor radiative decay but prevent non-radiative decay. • Formed excimers are emissive. [ABSTRACT FROM AUTHOR]

The optical transition properties of Tm3+ in oxyfluoride tellurite glass were determined by the Judd–Ofelt theory. The radiative transition rates, fluorescence branching ratios, and intrinsic lifetime for interesting transitions or level were obtained. The optimum doping concentration of Tm3+ for sample was examined, and the optimal concentration for upconversion luminescence was 0.1% Tm 2 O 3. The main reason for concentration quenching was nonradiative energy transfer through the cross-relaxation mechanism. In addition, two-photon processes for near-infrared 3H 4 →3H 6 emission and three-photon processes for blue 1G 4 →3H 6 emission of Tm3+ were confirmed by analyzing the dependence of upconversion intensities on the 980 nm fiber laser. The temperature-sensing properties of Tm3+ in oxyfluoride tellurite glass were investigated using 3F 2,3 → 3H 6 (698 nm) and 3H 4 →3H 6 (801 nm) excited at 980 nm, and the 3F 2,3 and 3H 4 states of Tm3+ were thermally coupled levels. • Optical transition properties of Tm3+ in the studied fluorescent glass were evaluated. • 1G 4.→3H 6 emission of Tm3+ is a three photon process and the upconversion near-infrared 3H 4 →3H 6 emission is a two-photon process under 980 nm irradiation. • The temperature sensing properties of Tm3+ in oxyfluoride tellurite glass were investigated by using 3F 2,3 and 3H 4 as thermal coupling energy levels excited at 980 nm. [ABSTRACT FROM AUTHOR]

In this study, the laser sintering technique was used to obtain Er3+/Yb3+ co-doped silica glasses for up-conversion (UC) luminescence for the first time. Further, structural analysis of the glass sample was conducted via XRD, SEM and EDS measurements. Based on the measured absorption spectrum, important spectroscopic parameters including three intensity parameters Ω t (t = 2, 4 and 6), theoretical and experimental line strengths, spontaneous transition probabilities, branching ratios and radiative lifetimes, were calculated using the Judd-Ofelt (J-O) theory. The UC properties of Er3+/Yb3+ co-doped silica glasses were investigated upon the excitation of a 976 nm laser. It has been experimentally confirmed that the green and red UC luminescences corresponding to the radiative transitions of Er3+: 2H 11/2 → 4I 15/2 (green), 4S 3/2 → 4I 15/2 (green) and 4F 9/2 → 4I 15/2 (red) were achieved. This result is consistent with those of the J-O theoretical analysis. Additionally, the energy transfer mechanism between Er3+ and Yb3+, which is responsible for the UC process, was discussed based on their dependence on the pump power. The obtained results indicated that the Er3+/Yb3+ co-doped silica glasses manufactured using the laser sintering technique can be promising for the application of short-wavelength lasers. • A non-CVD method, namely the laser sintering technique, was adopted. • Er3+/Yb3+ co-doped UC luminescent silica glasses was fabricated. • The silica glasses have exhibited excellent optical and spectroscopic properties. • Strong UC emissions were experimentally observed. • The experimental result is in agreement with those of the J-O theoretical analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • New Bi 2 O 3 -B 2 O 3 -Ga 2 O 3 -GeO 2 -TeO 2 -SiO 2 glass system doped with Dy3 + ions were prepared. • XRD, FTIR, UV/Vis/NIR and emission were studied. • Y/B and Ω2/Ω6 ratio indicated that the all glass samples as a perfect white light. The authors aim to study multi former oxide glasses doped with different concentrations of Dy3+ (0.00, 0.5, 1.0, 1.5, and 2 mol%) for white light-emitting application. All samples characterized by XRD, FTIR, and optical properties (absorption, excitation, and emission). The optical band gap calculated by a differential method. FTIR spectra confirm the network composed of GaO4, GeO4, TeO4, and BO4 tetrahedra, BO3 triangles, B-O-B linkages, and SiO4 tetrahedra with one NBO. In addition to the TeO3, BiO3, TeO6, and BiO6 vibration groups. Oscillator strengths and Judd–Ofelt parameters (Ω2, Ω4, Ω6) calculated and found that the glass samples had a variable trend from Ω2 > Ω4 > Ω6 to Ω2 > Ω6 > Ω4, at a Dy 2 O 3 content >1 mol%. Furthermore, radiative emission transition probability (AR), branching ratio (βR), and radiative lifetime (τR) estimated for Dy3+ ion in various excited states using J–O parameters. Upon 454 nm excitation, 4F 9/2 → 6H 15/2 [483 nm (blue)], 4F 9/2 → 6H 13/2 [575 nm (yellow)], and 4F 9/2 → 6H 11/2 [680 nm (red)] emission. Among them, it noticed that the transition 4F 9/2 → 6H 13/2 shows the highest intensity. The CIE chromaticity coordinates, correlated color temperature (CCT), and color purity (CP) indicate a generally neutral white light emission from all samples, which meant their suitability for optical applications. Determination of the white light coordinated from the CIE program, which verifies the values of samples are close to the pure white light. And sample containing 2 mol% Dy3+ close to the standard CIE D65 glow. [ABSTRACT FROM AUTHOR]

Abstract: The absorption edge of undoped Tl2Ga2S3Se crystals have been studied through transmission and reflection measurements in the wavelength range 440–1100nm and in the temperature range 10–300K. The absorption edge was observed to shift toward lower energy values with increasing temperature. As a result, the rate of the indirect band gap variation with temperature γ=−2.6×10−4 eV/K and the absolute zero value of the band gap energy E gi(0)=2.42eV were obtained. The emission band spectra of Tl2Ga2S3Se crystals have been studied in the temperature range 10–60K and in the wavelength region 505–605nm. A broad photoluminescence (PL) band centered at 550nm (2.25eV) was observed at T=10K. Variation of emission band has been studied as a function of excitation laser intensity in the 0.3–41.5mWcm−2 range. Radiative transitions from the shallow donor level E d=0.01eV to the moderately deep acceptor level E a=0.16eV were suggested to be responsible for the observed PL band. [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]

The article focuses on the study for the optical properties of colloidal photonic crystals (CPhCs). It discusses the fabrication techniques for CPhCs as well as their structures, photonic band gap, and fluorescence. It highlights the influence of photonic band gap, matching the energy of radiative transition, on the suppression of emission, which is used in resonance energy transfer; thus, improves photonic crystal (PhC)'s optical confinement.

A new scheme of water cloud optical properties is proposed for correlated k-distribution (CKD) models, in which the correlation in spectral distributions between the gaseous absorption coefficient and cloud optical properties is maintained. This is an extension of the CKD method from gas to cloud by dealing with the gas absorption coefficient and cloud optical properties in the same way. Compared to the results of line-by-line benchmark calculations, the band-mean cloud optical property scheme can overestimate cloud solar heating rate, with a relative error over 30%% in general. Also, the error in the flux at the top of the atmosphere can be up to 20 W m−2 at a solar zenith angle of 0°. However, the error is considerably reduced by applying the new proposed CKD cloud scheme. The physical explanation of the large error for the band-mean cloud scheme is the absence of a spectral correlation between the gaseous absorption coefficient and the cloud optical properties. The overestimation of the solar heating rate at the cloud-top layer could affect the moisture circulation and limit the growth of cloud. It is found that the error in the longwave cooling rate caused by the band-mean cloud scheme is very small. In the infrared, the local thermal emission strongly affects the spectral distribution of the radiative flux, which makes the correlation between the gaseous absorption coefficient and cloud optical properties very weak. Therefore, there is no obvious advantage in emphasizing the spectral correlation between gas and cloud. [ABSTRACT FROM AUTHOR]

Abstract: Mono-dispersed microspheres of ternary complex Eu(DBM)3phen (DBM=dibenzoylmethide; phen=1,10-phenanthroline) were prepared through a facile process. The obtained sample was characterized by means of X-ray powder diffraction (XRD) and scanning electron microscope (SEM). And the luminescence properties of the Eu(DBM)3phen were investigated by the fluorescence spectra and the fluorescence decay. According to Judd–Ofelt theory, the optical transition intensity parameters Ω λ (λ=2, 4 and 6) were obtained to be 20.99×10−20, 0.98×10−20 and 1.79×10−20 cm2, respectively. The radiative transition properties of 5D0 level, including transition rates, branch ratios and radiative transition lifetime were calculated. As a potential material for microsphere lasers, the optical gain performance for 5D0→7F2 transition was also evaluated. [Copyright &y& Elsevier]

Abstract: Dy3+ doped boro-tellurite glasses were prepared by following melt quenching technique with the chemical composition (69− x)H3BO3 + xTeO2 +15Mg2CO3 +15K2CO3 +1Dy2O3 (where x =0, 10, 20, 30 and 40wt%) by varying the tellurium dioxide content. The structural and optical properties have been studied through XRD, FTIR, absorption, luminescence and decay time measurements. The XRD pattern has been used to confirm the amorphous nature of the prepared glasses. The FTIR spectra reveals the presence of B–O vibrations and Te–O stretching modes of TeO3 and TeO6 units in the prepared glasses. The UV–vis–NIR absorption spectra were used to calculate the oscillator strength, bonding parameters ( and δ) and Judd–Ofelt intensity parameters (Ω λ , λ =2, 4 and 6). The radiative transition probability (A), stimulated emission cross section and the experimental, calculated branching ratios (β R) have been calculated from the luminescence spectra corresponding to 4F9/2 → 6H11/2, 6H13/2, and 6H15/2 excited state transitions. The structural and optical properties corresponding to the compositional changes were discussed and compared with the similar studies. [Copyright &y& Elsevier]

Abstract: In this research we prepared Zn2SiO4:Eu3+ phosphor nanopowders using a combination of sol–gel and combustion synthesis with the aim to examine the influence of synthesis conditions on the optical properties of the phosphor. As combustion fuels we used polyethylene glycol (PEG) with different average molecular weights, and the combustion was performed in two ways—in a microwave oven and a conventional furnace. Optical properties were examined by photoluminescence spectroscopy and spectra of all samples showed intense red emission, typical for f–f electronic transitions of the Eu3+ ions. Emission decays exhibited classical one exponential behavior at longer times and nonlinear nature at short times, with average lifetimes varied from 0.49 to 0.71ms between samples. Judd–Ofelt theory was applied to experimental data for the quantitative determination of optical parameters such as Ω 2,4 Judd–Ofelt parameters, radiative and nonradiative transition rates and emission quantum efficiency. Calculated parameters vary moderately between samples prepared with different PEGs and combusted in different manner. [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: 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: 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: Nd3+ doped fluorine containing zinc-aluminophosphate glasses have been prepared with alkali and alkaline earth content to understand the effect of network modifiers on radiative process. The physical and optical properties of these glasses have been evaluated. The Judd–Ofelt model for the intensity analysis of induced electric dipole transitions has been applied to the measured oscillator strengths of the absorption bands to determine the three phenomenological intensity parameters Ω 2, Ω 4 and Ω 6 for each glass. Using these parameters, transition probability (A), total transition probability (A T), branching ratios (β R) radiative life times (τ R) and integrated cross-section (σ a) for the stimulated emission have been theoretically calculated for certain excited Nd3+ fluorescent levels. From the obtained results the conclusion is made about the possibility of using these glasses as laser material. [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]

We have studied in detail the photoluminescence in type-II ZnSe/BeTe structures with large band offsets at high optical excitation levels. Our goal is a qualitative and quantitative description of the effect of a high carrier density on the spectral and kinetic properties of the photoluminescence in such structures. We have established that a high photoexcitation density leads to a significant spectral rearrangement of the spatially indirect radiative recombination, which also depends on the thickness of the structure layers. The spectral and kinetic characteristics of the indirect optical transitions in narrow and wide structures have been found to differ qualitatively. Our numerical calculations of the effect of macroscopic electric fields on the energy spectrum of free carriers at high densities of spatially separated charges, n > 1013 cm−2, give a qualitative and quantitative description of the experimentally observed photoluminescence properties. The calculations also show that the degree of localization of the above-barrier hole states grows significantly with n under conditions of increasing band bending, which should cause a weakening of the charge separation, especially in wide structures. In an experiment, the effect manifests itself in an enhancement of the spatially direct transition at a simultaneous weakening of the indirect transition both with increasing structure width and with increasing n. [ABSTRACT FROM AUTHOR]