1,721,574 research outputs found
Novel photonic glasses for fiber-optic amplifiers
No full textDevelopment of novel glass hosts for the fiber-optic amplifiers was introduced with a special attention on the O-band amplifiers operating at 1.31 mum. Upon the addition of alkali halide (especially CsBr) into Ge-Ga-S glasses, the intensity of the 1.31 mum emission from Dy3+ (F-6(11/2.).H-6(9/2) --> H-6(15/2)) increased sharply at the expense of the 1.75 mum emission intensity (H-6(11/2) --> H-6(15/2)). The lifetimes of the 1.31 mum emission level also increased up to 1580 mus. The nearest neighbors of Eu3+ ions, or rare-earth ions in this glass, are composed of halogen ions that are part of well-structured complex such as tetrahedral [GaS3/2Br](-) subunit and/or Ga2Br6 Similar enhancement in the emission properties was also observed in Tm3+ and Ho3+-doped glasses with the addition of an appropriate amount of CsBr into sulfide glasses.X11sciescopu
1.3-mu m-emission properties and local structure of Dy3+ in chalcohalide glasses
No full textSpectroscopic properties and local structure of rare-earth ions in Ge-Ga-S glasses with the addition of alkali halides were investigated. The intensity of the 1.31-mum emission from Dy3+ (F-6(11/2) H-6(9/2) --> H-6(15/2)) increased sharply when the appropriate. amount of alkali halides was added, at the expense of the 1.75-mum emission intensity (H-6(11/2) -->H-6(15/2)). The lifetimes of the 1.31-mum emission level also increased as much as 35 times from 38 mus for Ge-Ga-S glass (0.1 at.% Dy3+) to 1320 mus for glass containing 10 mol% of CsBr. These enhancements occurred only when the ratio of MX(M = K,Cs and X = Br, I)/Ga was equal to or larger than unity. Phonon side band (PSB) showed that the several local phonon modes, with the frequencies around 100 cm(-1), were coupled to 4f electrons of Eu3+. The nearest neighbors of Eu3+ ions are composed of halogen ions that are part of well-structured complex such as EuCl3, tetrahedral [GaS3/2Cl](-) subunit and/or Ga2Cl6. A small amount of As was added to increase the resistivity against the recrystallization during re-heating. The best composition for practical usage was 0.7 [Ge0.25As0.10S0.65]-0.15 GaS3/2-0.15 CsBr. This glass also exhibited high resistance against the attack of liquid water and is therefore a potential material for efficient fiber-optic amplifiers.X1113sciescopu
Emission and local structure of rare-earth ions in chalcogenide glasses
No full textLocal 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 245 cm(-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 similar to 6 Br ions in the glass with 10 mol% of CsBr. (C) 2007 Elsevier B.V. All rights reserved.X1111sciescopu
Rare-earth doped chalcogenide glasses for fiber-optic amplifiers
No full textEmission properties associated with the fiber-optic 6 amplification in Ge-Ga-S-CsBr glasses were investigated. The intensity of the 1.31 mum emission from Dy3+ (F-6(11/2) . H-6(9/2) --> H-6(15/2)) increased sharply when the appropriate concentrations of alkali halides were added, at the expense of the 1.75 mum emission intensity (H-6(11/2) --> H-6(11/2)). The lifetimes of the 1.31 mum emission level also increased up to 1580 mus. A small amount of As was added to increase the resistivity against the recrystallization during re-heating. The optimum composition for practical usage was 0.7[Ge0.25As0.10S0.65]-0.15GaS(3/2)-0.15CsBr. Phonon side band showed that the several local phonon modes, with the frequencies around 100 cm(-1), were coupled to 4f electrons of Eu3+. The nearest neighbors of Eu3+ ions are composed of halogen ions that are part of well-structured complex such as tetrahedral [GaS3/2Br](-) subunit and/or Ga2Br6. (C) 2003 Elsevier B.V. All rights reserved.X1125sciescopu
Band Gap and Diameter Modulation of Quantum Dots in Glasses
No full textModulation of the band gap energy and diameter of quantum dots (QDs) formed in glasses is important to achieve the optimized performance for applications as infrared light sources, lasers, saturable absorbers, etc. Absorption and photoluminescence of PbS QDs were extended into mid-infrared wavelength range in glasses containing small amount of lead but oversaturated with sulfur. Dual-band photoluminescence of PbSe QDs was prepared in oxyfluoride glass-ceramics containing BaF2 nanocrystals. By introducing SnO in the glasses, alloyed Pb1-xSnxSe QDs with smaller band gap energies were formed in glasses, and mid-infrared photoluminescence of Pb1-xSnxSe QDs at similar to 2570 nm in wavelength was achieved.1121sciescopu
Calcium-borosilicate glass-ceramics wasteforms to immobilize rare-earth oxide wastes from pyro-processing
No full textGlass-ceramics containing calcium neodymium(cerium) oxide silicate [Ca2Nd8-xCex(SiO4)(6)O-2] crystals were fabricated for the immobilization of radioactive wastes that contain large portions of rare-earth ions. Controlled crystallization of alkali borosilicate glasses by heating at T >= 750 degrees C for 3 h formed hexagonal Caesilicate crystals. Maximum lanthanide oxide waste loading was >26.8 wt.%. Ce and Nd ions were highly partitioned inside Caesilicate crystals compared to the glass matrix; the rare-earth wastes are efficiently immobilized inside the crystalline phases. The concentrations of Ce and Nd ions released in a material characterization center-type 1 test were below the detection limit (0.1 ppb) of inductively coupled plasma mass spectroscopy. Normalized release values performed by a product consistency test were 2.64.10(-6) g m(-2) for Ce ion and 2.19.10(-6) g m(-2) for Nd ion. Results suggest that glass-ceramics containing calcium neodymium(cerium) silicate crystals are good candidate wasteforms for immobilization of lanthanide wastes generated by pyro-processing. (C) 2015 Elsevier B.V. All rights reserved.1165sciescopu
Mechanism of the room-temperature persistent spectral hole burning in borate glasses doped with Eu3+
No full textSpectroscopic properties and room-temperature persistent spectral hole burning mechanisms of Eu3+-doped borate glasses were investigated. The depth of the burnt hole increased with the amount of carbon powders (i.e., degree of reducing atmosphere). This was attributed to the formation of defects which can donate free electrons for the photoreduction of Eu3+-->Eu2+. Holes survived >10(4) s at 20 K and approximately 40% of hole areas were preserved after annealing at 280 K. The photoreduction of Eu3+ to Eu2+ is a primary mechanism of hole burning and this hypothesis was supported by spectral hole properties, relaxation properties as well as changes in the local structure of Eu3+ in glasses. (C) 2002 American Institute of Physics.open1133sciescopu
Midinfrared emission properties of Pr3+-doped chalcogenide glasses at cryogenic temperature
No full textLow-temperature midinfrared emission properties of Pr3+-doped Ge30Ga2As6S62 and Ge28Ga5As12Se55 glasses (at. %) were investigated. Emissions centered at 3400 and 4700 nm were clearly observed from sulfide and selenide glasses, respectively, when the specimens were cooled to 20 K. The measured lifetime of the (1)G(4) level in sulfide glass increased from 320 mus at room temperature to 400 mus at 20 K. The intensity and quantum efficiency of the emission from the Pr3+:(F-3(3), F-3(4)) level in selenide glass also increased as the temperature decreased to 120 K. The enhancement resulted from a decrease in nonradiative multiphonon relaxation at low temperatures. The temperature dependence of the multiphonon relaxation rates indicated that the asymmetrical stretching vibration of GeS4 tetrahedra (375 cm(-1)) is primarily responsible for the multiphonon relaxation process in sulfide glass. (C) 2003 American Institute of Physics.open11109sciescopu
Precipitation of PbS quantum dots in glasses by thermal diffusion of Ag+ ions from silver pastes
No full textPrecipitation of PbS quantum dots (QDs) in glasses was controlled by thermal diffusion of Ag+ ions from Ag paste at a temperature of 320 degrees C After subsequent heat treatment at 420-450 degrees C, PbS QDs formed in the near-surface regions where the silver paste was applied. After the glasses were heat-treated at 440 or 450 degrees C, PbS QDs were larger in Ag-affected surface regions than in Ag-free glasses. PbS QDs grew in Ag-affected regions when they were heat-treated at 420 or 430 degrees C. Ag+ ions penetrated similar to 25 mu m from the glass surface after thermal diffusion of Ag+ ions and subsequent heat treatment at 430 degrees C. Thermal diffusion of Ag+ ions from Ag paste is a viable method to control the precipitation and spatial distribution of PbS QDs in glasses. (C) 2014 Elsevier B.V. All rights reserved.X1165sciescopu
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