Spectra and long-lasting properties of Sm3+-doped yttrium oxysulfide phosphor

We reported, for the first time to the best of our knowledge, the Sm3+ -doped yttriurn oxysulfide phosphors has reddish orange long-lasting phosphorescence. The phosphor show prominent luminescence in reddish orange due to the electronic transitions of (4)G(5/2) --> H-6(J) (J = 5/2, 7/2, 9/2), the afterglow color of this type of phosphors is a mixture of the three above mentioned electronic transition emissions and have a little different when the concentration of the Sm3+ dopant changes. Synthesis procedure of the Sm3+-yttrium oxysulfide reddish orange phosphor through the flux fusion method with binary flux compositions was presented. The synthesized phosphors were analyzed using X-ray diffraction (XRD) to interpret the structural characterization. The XRD analysis result reveal that the Y2O2S:Sm3+ phosphor synthesized with a binary flux composition containing (S and Na2CO3 at a ratio of 1: 1 at 30 wt.% of total raw material) at 1050degreesC for 3 h was in single-phase. Luminescence properties of the Y2O2S:Sm3+ long-lasting phosphor was analyzed by measuring the excitation spectra, emission spectra and afterglow decay curve. The mechanism of the strong afterglow from Y2O2S:Sm3+ was also discussed in this paper.

Spectroscopic features of erbium-doped CaM2O6 (M = Nb, Ta) single crystal fibers grown by the laser-heated pedestal growth technique

Erbium-doped single crystal fibers, with low phonon energy and fairly high absorption and emission cross sections are interesting laser active media, for compact, near-infrared and/or upconversion lasers. In this work, high optical quality Er3+-doped CaNb2O6 and CaTa2O6 single crystal fibers were successfully grown by the versatile laser-heated pedestal growth technique, and characterized from the structural and spectroscopic points of view. The results indicate that these crystal fiber compositions, which had not been explored so far, offer potential applications, not only as laser active media, but also in other optical devices. (c) 2007 Elsevier B.V. All rights reserved.

The temperature coefficient of the optical path length as a function of the temperature in different optical glasses

An interferometric technique was used to determine the temperature coefficient of the optical path length (dS/dT) as a function of the temperature in several optical glasses. The temperature range was between 25degreesC and 180degreesC. The studied samples included undoped and doped oxide glasses, such as low silica calcium aluminosilicate, phosphates, borates and also chalcogenides. The oxide glasses had dS/dT between 10 X 10(-6) K-1 and 20x10(-6) K-1, while for the chalcogenides, these were around 70 x 10(-6)K(-1). The results showed that dS/dTs increased with the temperature in all samples. For samples doped with Nd the dS/dT values were found to be independent of concentration. on the other hand, for the phosphate glass doped with Cr, dS/dT increased about 5% when compared with the Nd doped one. In conclusion, the used interferometric method, which is a considerably simpler and a lower cost technique, and is a useful tool to measure dS/dT in semi-transparent glasses as a function of the composition and temperature. (C) 2004 Elsevier B.V. All rights reserved.

Production of defects in ZBLAN, ZBLAN : Tm3+ and ZBLAN : Cr3+ glasses by ultra-short pulses laser interaction

In this work we have studied pure and thulium- and chromium-doped ZBLAN glasses irradiated by ultra-short laser pulses. A Ti:sapphire CPA system was used, producing a 500 Hz train of pulses, centered at 830 nm, with 375 mu J of energy and 50 fs of duration (FWHM). The beam was focused by a 20 Him lens, producing a converging beam with a waist of 12 pin. The absorption spectra before and after laser irradiation were obtained showing production of color centers in pure, thulium-doped and chromium-doped ZBLAN glasses. A damage threshold of 9.56 TW/cm(2) was determined for ZBLAN. (C) 2007 Elsevier Ltd. All rights reserved.

Upconversion of infrared-to-visible light in Pr3+-Yb3+ codoped fluoroindate glass

Bright fluorescence in the visible range has been observed in Pr3+-Yb3+ doped fluoroindate glass under infrared diode laser irradiation. The mechanism which contributes for the upconversion emission is identified and the energy transfer rate between Pr3+-Yb3+ is obtained for different concentrations. © 1998 Elsevier Science B.V. All rights reserved.

Tunable plasmon resonance modes on gold nanoparticles in Er 3 +-doped germanium-tellurite glass

Relative to the Er3 +:gold-nanoparticle (Er3 +:Au-NP) axis, the polarization of the gold nanoparticle can be longitudinal (electric dipole parallel to the Er3 +:Au-NP axis) or transverse (electric dipole perpendicular to the Er3 +:Au-NP axis). For longitudinal polarization, the plasmon resonance modes of gold nanoparticles embedded in Er3 +-doped germanium-tellurite glass are activated using laser lines at 808 and 488 nm in resonance with radiative transitions of Er3 + ions. The gold nanoparticles were grown within the host glass by thermal annealing over various lengths of time, achieving diameters lower than 1.6 nm. The resonance wavelengths, determined theoretically and experimentally, are 770 and 800 nm. The absorption wavelength of nanoparticles was determined by using the Frohlich condition. Gold nanoparticles provide tunable emission resulting in a large enhancement for the 2H11/2 → 4I13/2 (emission at 805 nm) and 4S 3/2 → 4I13/2 (emission at 840 nm) electronic transitions of Er3 + ions; this is associated with the quantum yield of the energy transfer process. The excitation pathways, up-conversion and luminescence spectra of Er3 + ions are described through simplified energy level diagrams. We observed that up-conversion is favored by the excited-state absorption due to the presence of the gold nanoparticles coupled with the Er3 + ions within the glass matrix. © 2013 Elsevier B.V.

Vidros a base de óxido de telúrio para dispositivos fotônicos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conversão descendente de energia envolvendo íons lantanídeos. Vidros emissores de luz na região de 1000 nm

Pós-graduação em Química - IQ

Focusing surface plasmons on Er3+ ions through gold planar plasmonic lenses

Gold plasmonic lenses consisting of a planar concentric rings-groove with different periods were milled with a focused gallium ion beam on a gold thin film deposited onto an Er3+-doped tellurite glass. The plasmonic lenses were vertically illuminated with an argon ion laser highly focused by means of a 50x objective lens. The focusing mechanism of the plasmonic lenses is explained using a coherent interference model of surface plasmon-polariton (SPP) generation on the circular grating due to the incident field. As a result, phase modulation can be accomplished by the groove gap, similar to a nanoslit array with different widths. This focusing allows a high confinement of SPPs that can excite the Er3+ ions of the glass. The Er3+ luminescence spectra were measured in the far-field (500-750 nm wavelength range), where we could verify the excitation yield via the plasmonic lens on the Er3+ ions. We analyze the influence of the geometrical parameters on the luminescence spectra. The variation of these parameters results in considerable changes of the luminescence spectra.

Highly Efficient IR to NIR Upconversion in Gd2O2S: Er3+ for Photovoltaic Applications

Upconversion (UC) is a promising option to enhance the efficiency of solar cells by conversion of sub-bandgap infrared photons to higher energy photons that can be utilized by the solar cell. The UC quantum yield is a key parameter for a successful application. Here the UC luminescence properties of Er3+-doped Gd2O2S are investigated by means of luminescence spectroscopy, quantum yield measurements, and excited state dynamics experiments. Excitation into the maximum of the 4I15/2 → 4I13/2 Er3+ absorption band around 1500 nm induces very efficient UC emission from different Er3+ excited states with energies above the silicon bandgap, in particular, the emission originating from the 4I11/2 state around 1000 nm. Concentration dependent studies reveal that the highest UC quantum yield is realized for a 10% Er3+-doping concentration. The UC luminescence is compared to the well-known Er3+-doped β-NaYF4 UC material for which the highest UC quantum yield has been reported for 25% Er3+. The UC internal quantum yields were measured in this work for Gd2O2S: 10%Er3+ and β-NaYF4: 25%Er3+ to be 12 ± 1% and 8.9 ± 0.7%, respectively, under monochromatic excitation around 1500 nm at a power of 700 W/m2. The UC quantum yield reported here for Gd2O2S: 10%Er3+ is the highest value achieved so far under monochromatic excitation into the 4I13/2 Er3+ level. Power dependence and lifetime measurements were performed to understand the mechanisms responsible for the efficient UC luminescence. We show that the main process yielding 4I11/2 UC emission is energy transfer UC.

Numerical modeling of holmium-doped fluoride fiber lasers

We combine all the known experimental demonstrations and spectroscopic parameters into a numerical model of the Ho3+ -doped fluoride glass fiber laser system. Core-pumped and cladding-pumped arrangements were simulated for all the population-bottlenecking mitigation schemes that have been tested, and good agreement between the model and the previously reported experimental results was achieved in most but not in all cases. In a similar way to Er3+ -doped fluoride glass fiber lasers, we found that the best match with measurements required scaled-down rate parameters for the energy transfer processes that operate in moderate to highly concentrated systems. The model isolated the dominant processes affecting the performance of each of the bottlenecking mitigation schemes and pump arrangements. It was established that pump excited-state absorption is the main factor affecting the performance of the core-pumped demonstrations of the laser, while energy transfer between rare earth ions is the main factor controlling the performance in cladding-pumped systems.

Structural characterisation of hypoxia-mimicking bioactive glasses

Nickel and cobalt are both known to stimulate the hypoxia-inducible factor-1 (HIF-1a), thus significantly improving blood vessel formation in tissue engineering applications. We have manufactured nickel and cobalt doped bioactive glasses to act as a controlled delivery mechanism of these ions. The resultant structural consequences have been investigated using the methods of isotopic and isomorphic substitution applied to neutron diffraction. The structural sites present will be intimately related to their release properties in physiological fluids such as plasma and saliva, and hence the bioactivity of the material. Detailed structural knowledge is therefore a prerequisite for optimising material design. Results show that nickel and cobalt adopt a mixed structural role within these bioactive glasses occupying both network-forming (tetrahedral) and network-modifying (5-fold) geometries. Two thirds of the Ni (or Co) occupies a five-fold geometry with the remaining third in a tetrahedral environment. A direct comparison of the primary structural correlations (e.g. Si-O, Ca-O, Na-O and O-Si-O) between the archetypal 45S5 Bioglass® and the Ni and Co glasses studied here reveal no significant differences. This indicates that the addition of Ni (or Co) will have no adverse effects on the existing structure, and thus on in vitro/in vivo dissolution rates and therefore bioactivity of these glasses.

The role of glass modifiers in the solubility of Tm3+ ions in As2S3 glasses

Au cours des années une variété des compositions de verre chalcogénure a été étudiée en tant qu’une matrice hôte pour les ions Terres Rares (TR). Pourtant, l’obtention d’une matrice de verre avec une haute solubilité des ions TR et la fabrication d’une fibre chalcogénure dopée au TR avec une bonne qualité optique reste toujours un grand défi. La présente thèse de doctorat se concentre sur l’étude de nouveaux systèmes vitreux comme des matrices hôtes pour le dopage des ions TR, ce qui a permis d’obtenir des fibres optiques dopées au TR qui sont transparents dans l’IR proche et moyenne. Les systèmes vitreux étudiés ont été basés sur le verre de sulfure d’arsenic (As2S3) co-dopé aux ions de Tm3+ et aux différents modificateurs du verre. Premièrement, l’addition de Gallium (Ga), comme un co-dopant, a été examinée et son influence sur les propriétés d’émission des ions de Tm a été explorée. Avec l’incorporation de Ga, la matrice d’As2S3 dopée au Tm a montré trois bandes d’émission à 1.2 μm (1H5→3H6), 1.4 μm (3H4→3F4) et 1.8 μm (3F4→3H6), sous l’excitation des longueurs d’onde de 698 nm et 800 nm. Les concentrations de Tm et de Ga ont été optimisées afin d’obtenir le meilleur rendement possible de photoluminescence. À partir de la composition optimale, la fibre Ga-As-S dopée au Tm3+ a été étirée et ses propriétés de luminescence ont été étudiées. Un mécanisme de formation structurale a été proposé pour ce système vitreux par la caractérisation structurale des verres Ga-As-S dopés au Tm3+, en utilisant la spectroscopie Raman et l’analyse de spectrométrie d’absorption des rayons X (EXAFS) à seuil K d’As, seuil K de Ga et seuil L3 de Tm et il a été corrélé avec les caractéristiques de luminescence de Tm. Dans la deuxième partie, la modification des verres As2S3 dopés au Tm3+, avec l’incorporation d’halogénures (Iode (I2)), a été étudiée en tant qu’une méthode pour l’adaptation des paramètres du procédé de purification afin d’obtenir une matrice de verre de haute pureté par distillation chimique. Les trois bandes d’émission susmentionnées ont été aussi bien observées pour ce système sous l’excitation à 800 nm. Les propriétés optiques, thermiques et structurelles de ces systèmes vitreux ont été caractérisées expérimentalement en fonction de la concentration d’I2 et de Tm dans le verre, où l’attention a été concentrée sur deux aspects principaux: l’influence de la concentration d’I2 sur l’intensité d’émission de Tm et les mécanismes responsables pour l’augmentation de la solubilité des ions de Tm dans la matrice d’As2S3 avec l’addition I2.

Investigations into the structural and down-shifting and up-conversion luminescence properties of Ba2Na1-3xErxNb5O15 (0 <= x <= 0.06) nanocrystalline phosphor synthesized via sol-gel route

The present work deals with the structural and efficient down-shifting (DS) and up-conversion (UC) luminescence properties of erbium ion (Er3+) doped nanocrystalline barium sodium niobate (Ba2Na1-3xErxNb5O15, where x = 0, 0.02, 0.04 and 0.06) powders synthesized via novel citrate-based sol-gel route. The monophasic nature of the title compound was confirmed via x-ray powder diffraction followed by FT-IR studies. High-resolution transmission electron microscopy (HRTEM) facilitated the establishment of the nanocrystalline phase and the morphology of the crystallites. The Kubelka-Munk function, based on diffused reflectance studies and carried out on nano-sized crystallites, was employed to obtain the optical band-gap. The synthesized nanophosphor showed efficient DS/PL-photoluminescence and UC luminescence properties, which have not yet been reported so far in this material. The material emits intense DS green emission on excitation with 378 nm radiation. Interestingly, the material gives intense UC emission in the visible region dominated by green emission and relatively weak red emission on 976 nm excitation (NIR laser excitation). Such a dual-mode emitting nanophosphor could be very useful in display devices and for many other applications.

固着磨料加工工艺对磷酸盐钕玻璃亚表面缺陷的影响

散粒磨料研磨与固着磨料研磨是光学研磨加工过程中的两种主要手段,但两者材料去除的机制不同。目前针对高功率固体激光装置中的主要工作物质——磷酸盐激光钕玻璃的亚表面缺陷(SSD)研究相对较少,因此在实验的基础上,通过系统地研究固着磨料对磷酸盐激光钕玻璃的研磨工艺过程,分析了多种因素,如磨料粒径、载荷大小、机床转速,以及结合剂材料与冷却液等对钕玻璃亚表面缺陷形成的影响,并与散粒磨料研磨工艺所产生的亚表面缺陷进行了比较,对关键工艺参数进行定量,为高质量钕玻璃制造工艺的选型以及进一步优化亚表面缺陷提供了重要的参考数据。