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Cd‐S‐Se quantum dot embedded glasses (QDEGs) with dual‐band emissions of green and red were synthesized by assembling two QDEGs, to obtain a color converter for white LEDs (wLEDs) with a wide color gamut and long‐term stability. Each QDEG, possessing different sizes of QD, was prepared by adjusting heat‐treatment conditions. They were then bonded to each other by an additional heat treatment to fabricate a pattern structured QDEG (pQDEG). The fabrication conditions of the pQDEGs, such as their heat‐treatment condition and thickness, were varied to improve the color gamut. pQDEG‐based WLEDs were demonstrated and their optical properties such as color coordinates, luminous efficiency, and color rendering index (CRI) were monitored. The effect of pQDEG fabrication conditions on the resultant emission spectra and color gamut were discussed. [ABSTRACT FROM AUTHOR]

Abstract: Infrared upconversion luminescence properties of Er3+/Yb3+ co-doped oxy-fluoride glasses and glass-ceramics were investigated. Under 1550nm laser excitation, infrared emission centered at ~980nm that originated from the Yb3+: 2F5/2 → 2F7/2 and Er3+: 4I11/2 → 4F15/2 transitions was observed. The upconversion luminescence was enhanced both by Yb3+ content increase and by precipitation of β-PbF2 nano-crystals in the glass matrix. The energy transfer process between Yb3+ and Er3+ ions dominated IR upconversion emission, and Yb3+ can be used as energy acceptor. The strong upconverted luminescence can be used to increase the efficiency of silicon solar cells. [Copyright &y& Elsevier]

Luminescence of CdS quantum dots ( QDs) enhanced by the induction of Ag nanoparticles ( NPs) in glasses was investigated. Ag+ ions diffused into glasses containing CdS QDs by ion exchange, then formed Ag NPs after subsequent heat treatment. Luminescence intensity of CdS QDs increased approximately three times when the ion-exchange duration was 1 min, but was severely quenched when the duration was extended to 30 min. Increasing the amount of Ag+ ions increased the number of Ag NPs and decreased the average distance between Ag NPs and CdS QDs. This decrease in the average distance induced the changes of luminescence intensity. [ABSTRACT FROM AUTHOR]

Abstract: We experimentally verify that a color center in the form of takes shape in silicate glasses containing relatively small amount of ZnSe which are prepared via a conventional melt-quenching process. Samples also produce broad photoluminescence when excited with UV light source, suggesting potential applications in the visible range. Analyses based on X-ray diffraction patterns, high resolution transmission electron microscopy, and Raman spectroscopy support the formation of color centers in addition to Se nanocrystals. [Copyright &y& Elsevier]

Abstract: Optical properties and photoluminescence of PbS quantum dots (QDs) embedded in glasses were investigated. Formation and radius of PbS QDs were carefully controlled though heat-treatment and modification of host glass composition. Heat-treatment conditions for precipitation of 3–10nm radius QDs for the tunable photoluminescence in the 1–2μm wavelength range were identified. Glasses doped with PbS QDs provide potential as robust materials for broadband fiber-optic amplifiers. [Copyright &y& Elsevier]

Abstract: Thermal treatment at 480 °C for 40 h resulted in the precipitation of β-PbF2 nano-crystals inside the oxy-fluoride glasses co-doped with Ho3+, Tm3+ and Yb3+. Generation of white light was achieved through the simultaneous blue, green and red up-converted emissions by pumping at 900 nm. Simulation of sunlight was most successfully achieved with pump power of ∼150 mW. [Copyright &y& Elsevier]

Abstract: Local structures of rare-earth ions in Ge–Ga–S–CsBr glasses were investigated to understand the structural origin on the emission property enhancement. The frequency of the phonon vibration controlling the multiphonon relaxation was changed to 245cm−1 due to the formation of Ga–Br bonds with CsBr addition to sulfide glasses. Formation of this new chemical bond was also confirmed from the phonon side band spectra of Eu3+ ions. Analyses of the EXASF spectra proved that Tm3+ ions were surrounded by approximately seven S ions in Ge0.25Ga0.10S0.65 glass but were coordinated by ∼6 Br ions in the glass with 10mol% of CsBr. [Copyright &y& Elsevier]

Abstract: Transparent nano-crystalline glass–ceramics (nano-structured glasses) were prepared from oxy-fluoride precursor glass doped with HoF3 and their luminescence properties were investigated. Visible blue, green and red emissions were observed, and the relative intensity of the green and red emission was strongly dependent on HoF3 concentration. Under 750 nm pumping, the intense green emission due to the photon avalanche process was observed at room temperature from nano-structured glass doped with high (0.5mol%) concentration of HoF3. [Copyright &y& Elsevier]

Various rare earth (RE) oxides such as Pr 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , and Er 2 O 3 were introduced into Cd–S–Se quantum dot embedded glasses (QDEGs) to investigate their effect on the color conversion properties of the Cd–S–Se QDEGs. The absorption and emission peak wavelengths due to the excitonic transition of the Cd–S–Se QDs were modified by the introduction of RE oxides, implying their influence on QD formation. The photoluminescence of the various QDEGs RE oxides under 450 nm excitation were monitored and compared with the un-doped QDEGs. White LEDs (wLEDs) were also fabricated with the RE-doped QDEGs and their color conversion properties, such as quantum yield (QY), luminous efficacy, correlated color temperature (CCT) and color rendering index (CRI) were examined. Transmission electron microscope (TEM) revealed that the size and spatial distribution of the QDs were improved by the RE-oxides. Their effect on QD formation within the silicate glass was discussed using Raman spectroscopy. • Cd–S–Se quantum dot embedded glasses (QDEG) with various rare earth (RE) ions were fabricated. • RE ions reduced QD size and modified spectral properties of QDEGs. • RE ions improved size and spatial distribution of QDs within glass matrix. • White LED was successfully achieved with RE-doped QDEGs. [ABSTRACT FROM AUTHOR]

The Er3+ concentration dependencies of upconversion luminescence in oxy-fluoride glass and glass-ceramics containing PbF2 nanocrystals were investigated. Strong red emission from the 4F9/2 → 4I15/2 transition was observed with the addition of ~0.8 mol% Er3+ ions, whereas ~10 mol% of Er3+ is required to achieve such emission in several other crystalline hosts. Intensities of red emission further increased with the formation of nanocrystals through heat treatment. The Er3+ ions enriched in glass and segregated preferentially inside the PbF2 nanocrystals that decreased the distance among Er3+ ions and thereby facilitated energy transfer. [ABSTRACT FROM AUTHOR]

Abstract: Optical properties of Er-doped chalcohalide GeGaS–CsBr glasses have been investigated as a function of Er and Ga concentrations. Nominal compositions of (Ge0.25Ga.0.10S0.65)0.9(CsBr)0.1 and (Ge0.23Ga.0.12S0.65)0.9(CsBr)0.1 glassy hosts have been chosen for this study. The effects of Er content and host composition on 1.5μm emission of Er3+ ions, measured at low-temperature of 20K under excitation by 514.5nm, have been specified. Besides, the up-conversion fluorescence of Er3+ ions pumped at 795nm is reported. Two intense emission bands in the green and one weak emission band in the red regions around 530, 554 and 644nm have been observed, and were attributed to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 transitions of Er3+ ions, respectively. The simplified energy-level diagram of Er3+ ion has been used to identify the observed up-conversion fluorescence bands in visible region. [ABSTRACT FROM AUTHOR]

Abstract: Optical properties of PbS quantum dots (QDs) precipitated inside the oxide glass matrix were investigated. Photoluminescence (PL) from the PbS QDs showed peak wavelengths located at 1170–1680nm with widths of 150–550nm. Radii of QDs in glasses were 2.3–4.7nm depending upon the thermal treatment. Peak wavelengths of PL bands shifted as much as 70nm as the temperatures and excitation irradiances increased. Calculated effective local temperatures indicated that these shifts of PL spectra were associated with local heating induced by the temperatures and laser beam. [Copyright &y& Elsevier]

Abstract: The formation of structural units in Ge–Ga–S glass with CsBr addition and its effect on the optical band gap and several spectroscopic properties of Ho3+ were investigated. The optical band gap of the host glasses and the oscillator strengths of Ho3+ absorption decreased sharply when the ratio of CsBr/Ga became close to unity. These property changes were associated with the formation of structural units of [GaS3/2Br]− and they have a crucial effect on the changes of the local structure around Ho3+ ions. The local structure was not sensitive to the As or Br addition but was critically dependent on the concentration of CsBr. [Copyright &y& Elsevier]

Abstract: The Pr3+: 1D2 → 1G4 transition in silica-based oxide glasses, which emits a strong luminescence centered at about 1530nm with full-width at half-maximum wider than 200nm, may reserve potential practicality owing to its fairly long fluorescence lifetime of ∼270μs corresponding to theoretical quantum efficiency approaching unity and its emission wavelengths matching up to the optical communication window of silica transmission fiber. To minimize non-radiative energy transfers among the active ions, the host materials need doping concentration of Pr2O3 tantamount to not more than 0.01mol%. Impact of ground state absorption to (3F3, 3F4) level on the emission is discussed and then efficient excitation schemes are proposed. [Copyright &y& Elsevier]

Abstract: PbSe quantum dots (QDs) were synthesized in borosilicate glass and their optical properties were investigated. The typical quantum confinement effects were clearly observed from the absorption when the average radii of the QDs changed from 1.7 to 3.1nm. Photoluminescence from PbSe QDs was achieved in 1.1–2.2μm wavelength region that covers the entire fiber-optic telecommunication window. Borosilicate glasses containing controlled size of PbSe QDs provide potentials for the fiber-optic amplifiers. [Copyright &y& Elsevier]

The effects of host glass composition on the upconversion luminescence of Nd 3 + doped (1 − x )(Ge 0.25 Ga 0.10 S 0.65 )– x (CsBr) chalcohalide glasses were investigated. Bright upconversion luminescence was observed in the 535 nm, 602 nm and 665 nm bands, with weak blue emission. Luminescence intensity increased with CsBr content x , and jumped when x increased from 0.08 to 0.10. Lifetimes of 4 G 7/2 level and 4 F 3/2 intermediate levels of Nd 3 + ions had similar dependency on CsBr content. Raman analysis proved that a [GaS 3/2 Br] − group formed due to CsBr addition. The effective phonon energy decreased from 375 cm − 1 ([Ga–S] bond vibration) to 245 cm − 1 ([Ga–Br] bond vibration) when CsBr/Ga ratio was > 1, which resulted in sudden changes in upconversion intensities and lifetimes. The results indicated that the chalcohalide glasses are promising candidates for use in applications that require efficient upconversion luminescence. [ABSTRACT FROM AUTHOR]

Highlights: [•] Blue, green and red emissions were observed from Ho3+ singly doped chalcohalide glasses. [•] White light from Ho3+ singly doped chalcohalide glasses were generated. [•] Color coordinates of white light generated were independent on excitation power. [Copyright &y& Elsevier]

Abstract: We experimentally verified, within silicate glasses, the formation of Se2 − color centers that are responsible for a broad visible emission under optical excitation at UV wavelengths. In addition to Raman spectra, all the spectroscopic analyses on absorption, photoluminescence, and photoluminescence excitation unanimously confirm the formation of Se2 − color centers. However, the visible absorption due to Se2 − color centers disppeared upon increasing concentration of Na2O, which implies that their formation would depend on the compositions of silicate glasses. The role of Na2O in the formation mechanism in relation to glass structure is then discussed in terms of various analyses on X-ray diffraction patterns, X-ray photoelectron spectroscopy, and Raman spectroscopy. [Copyright &y& Elsevier]

Abstract: Chalcohalide glass with a composition of 65GeS2–25Ga2S3–10CsI (in mol%) doped with 0.6wt% Tm3+ ions was prepared by conventional melt–quench method. By heat treating the precursor glass at 20°C above its glass transition temperature T g for different durations, IR transparent glass ceramics were obtained. X-ray diffraction (XRD) and scanning electron microscope (SEM) showed that Ga2S3 crystallites were precipitated after heat treatment and their grain sizes were in nano-scale and increased with the elongation of heat treated time. Mid-IR luminescence properties of the glass and transparent glass ceramic samples were investigated. The emissions at 2.3 and 3.8μm corresponding to optical transitions of 3 H 4 → 3 H 5 and 3 H 5 → 3 F 4 of Tm3+ ions were significantly enhanced by the presence of Ga2S3 nanocrystals and reached a maximum after 8hours treatment. [Copyright &y& Elsevier]

Abstract: From Dy L3-edge extended X-ray absorption fine structure spectroscopic analysis of Dy-doped Ge–As–S glass, we verified that both the coordination number and Dy–S distance are decreased in this representative chalcogenide glass compared to those in the Dy2S3 crystalline counterpart. The strong covalent nature inherent in chemical bonds between the constituent atoms of Ge–As–S glass would be responsible for the enhanced covalency of the Dy–S bonds, which would then be sensitively related to the optical characteristics of the 4f↔4f transitions of Dy3+ as well as the low rare-earth solubility exhibited by the Ge–As–S glass. [Copyright &y& Elsevier]

Abstract: Absorption transition from the ground 6H15/2 state to the superimposed (6H9/2, 6F11/2) states, inverse transition of which leads the Dy3+: 1.3μm luminescence, in noncrystalline Ge–As–S alloys is dramatically modified upon a least compositional adjustment by Ga and CsBr. The change in oscillator strength of the Dy3+: 6H15/2↔6F11/2 transition in our modified glasses is more sensitive to the local coordination structure of rare-earths compared to other hypersensitive transitions that have been previously observed in solid-state dielectric hosts. Preferential highly symmetric coordination in nearest-neighbouring shell of dysprosium with bromine in [GaS3/2Br]− complexes, which are formed spontaneously during vitrification process of the host materials, is believed to be responsible for the behaviour. [Copyright &y& Elsevier]

Abstract: The effect of CsBr/Ga ratio on the blue upconverted emission from Nd3+/Pr3+ in Ge–Ga–S–CsBr chalcohalide glasses was investigated. When CsBr/Ga was smaller than unity, the energy transfer from Nd3+ to Pr3+ ions was dominant and blue emission centered at ∼495nm (Pr3+:3P0 → 3H4) was observed. On the contrary, the intensity of the upconversion luminescence from Nd3+ increased at the expense of the blue emission when CsBr/Ga ratio exceeded unity. The possible relationship between the composition-dependent blue emission and the local environment of rare earth ions was discussed. [ABSTRACT FROM AUTHOR]