Gonul Eryurek

Spectroscopic investigation of zinc tellurite glasses doped with Yb3 + and Er3 + ions

This paper presents a detailed spectroscopic investigation of zinc tellurite glasses with the compositions (0.80-x-y) TeO2+(0.20) ZnO+xEr2O3+yYb2O3 (x=0, y=0; x=0.004, y=0; x=0, y=0.05 and x=0.004, y=0.05 per moles). The samples were synthesized by the conventional melt quenching method. The optical absorption and emission measurements were conducted at room temperature to determine the spectral properties of lanthanides doped zinc tellurite glasses and, to study the energy transfer processes between dopant lanthanide ions. The band gap energies for both direct and indirect possible transitions and the Urbach energies were measured from the absorption spectra. The absorption spectra of the samples were analyzed by using the Judd-Ofelt approach. The effect of the ytterbium ions on the emission properties of erbium ions was investigated and the energy transfer processes between dopant ions were studied by measuring the up-conversion emission properties of the materials. The color quality parameters of obtained visible up-conversion emission were also determined as well as possibility of using the Er(3+) glasses as erbium doped fiber amplifiers at 1.55μm in infrared emission region.

Blue cooperative upconversion and white light emission from Y 2 Si 2 O 7 :Yb 3+ nanopowders due to 975-nm infrared excitation

Abstract. We report the luminescence properties of undoped and 10% Yb3+-doped Y2Si2O7 nanopowders under the infrared excitation of 975-nm laser diode. A broadband white light (WL) emission is observed in the undoped powder, and its intensity becomes stronger with increasing excitation power. A blue emission centered at ∼475  nm is observed below the excitation power of ∼2  W in the Yb3+-doped sample. The blue emission intensity dependence on the excitation power suggests that this emission is a two-photon absorption process known as the cooperative luminescence of Yb3+ ions. When the excitation power is increased above 2 W, a broadband “white” emission extending from blue into the near infrared appears while the blue cooperative emission band of Yb3+ ions disappears. The excitation power dependence of the WL intensity at 758 nm is due to a multiphoton process that may be attributed to the thermal radiation mechanism. The International Commission on Illumination coordinates (x,y) for the WL emission in the Yb3+-doped Y2Si2O7 nanocrystalline sample is found to be (0.4503, 0.3999) and (0.5035, 0.4096) for 2.005- and 3.68-W excitation powers, respectively. These values lie in the yellowish region and correspond to the color temperature value of 5030 K, with a color rendering index of 85.

Luminescence properties of Nd3+/Yb3+ co-doped yttrium silicate nanophosphors excited by at laser diode of 975 nm

Trivalent rare earth ions doped materials can convert near infrared photons to different visible emissions and Yb3+ rare earth ions have only two levels of 2F7/2 and 2F5/2 in the near infrared region. Yb3+ ions are generally used as sensitizer to obtain high emissions from other rare earths by using ∼975 nm laser and the near infrared photon energy can be transferred from Yb3+ to other ions. The energy level 4F3/2 of Nd3+ is little higher than the 2F5/2 level of Yb3+, so Nd3+ emission may be sensitized by energy transfer from Yb3+ ion. In this work, we studied the luminescence properties of Nd3+/Yb3+ co-doped yttrium silicate (Y2O3:SiO2) nanopowder with a 975 nm diode laser excitation. The emission properties and spectral changes were analyzed at atmospheric pressure and vacuum. The decay and rise patterns were carried out under vacuum (0.01 mbar) and atmospheric pressures.

Structural, optical and photo thermal properties of Er3+:Y2O3 doped PMMA nanocomposite

Thermal decomposition technique was employed to synthesize of phosphors of yttria (Y2O3) doped with erbium (Er3+) ions. After the synthesized procedure, the nano-sized crystalline powders were annealed at 800oC for 24 h. Annealed powders were embedded in poly(methyl methacrylate) (PMMA) by free radical polymerization to fabricate nanocomposite polymer materials. The crystalline structure of the powder and doped PMMA nanocomposite samples were determined using X-ray diffraction technique. Scherrer’s equation and the FW1/5/4/5M method were used to determine average crystalline size and grain size distributions, respectively. The spectroscopic properties of the powders and doped PMMA nanocomposites were studied by measuring the upconversion emission spectra under near-infrared laser excitation at room temperature. The laser-induced photo thermal behaviors of Er3+:Y2O3 nano-powders and doped PMMA nanocomposite were investigated using the fluorescence intensity ratio (FIR) technique.Thermal decomposition technique was employed to synthesize of phosphors of yttria (Y2O3) doped with erbium (Er3+) ions. After the synthesized procedure, the nano-sized crystalline powders were annealed at 800oC for 24 h. Annealed powders were embedded in poly(methyl methacrylate) (PMMA) by free radical polymerization to fabricate nanocomposite polymer materials. The crystalline structure of the powder and doped PMMA nanocomposite samples were determined using X-ray diffraction technique. Scherrer’s equation and the FW1/5/4/5M method were used to determine average crystalline size and grain size distributions, respectively. The spectroscopic properties of the powders and doped PMMA nanocomposites were studied by measuring the upconversion emission spectra under near-infrared laser excitation at room temperature. The laser-induced photo thermal behaviors of Er3+:Y2O3 nano-powders and doped PMMA nanocomposite were investigated using the fluorescence intensity ratio (FIR) technique.

Solid State Synthesis, Structural and Up-Conversion Properties of Yb3+∕Er3+ and Yb3+∕Tm3+∕Er3+ Doped La2Ti2O7 Phosphors

In this work, Yb3+∕Er3+ co-doped and Yb3+∕Tm3+∕Er3+ tri-doped La2Ti2O7 phosphors were synthesized by solid-state reaction method. The phases of the powders were identified using the X-Ray Diffraction (XRD) technique. The purity of the La2Ti2O7 phosphors were tested by energy dispersive spectroscopy (EDS). The photoluminescence properties of La2Ti2O7 phosphors were investigated in the range of 400–850 nm wavelength under 975 nm laser excitation at room temperature. Presence of Tm3+ ion in the tri-doped powder effects the UC-emission processes observed in the powders co-doped with Yb3+∕Er3+.

Investigation of the Luminescence Spectral Profiles and the Efficiencies of Yb 3+ , Nd 3+ , Tm 3+ Doped Y 2 O 3 -SiO 2 Nano-phosphors

Among various developed UC luminescence materials, rare earth doped yttrium silicates (YSO) exhibit high chemical durability and thermal stability which are suitable for many applications such as lighting, lasers, optical sensors and biological applications. The reduction to nano size of such materials aims to investigate the issue of how the optical properties affected, and thus to further extend the use of these materials in photonic industry. The studies about the effect of nanoscale to the lattice- electron interaction is not yet enough to understand the mechanisms. For this reason, the influence of the various synthesis techniques to the size and the effect of the size of those nano-materials on the optical and thermal properties are basic research areas for various photonic device design and their developments.

Investigation of the White Light Emission from Er/Nd/Yb Rare Earth Oxides at Vacuum and Atmospheric Pressure

We present the production of white light emission with the monochromatic infrared light excitation of erbium oxide (Er2O3), ytterbium oxide (Yb2O3), and neodymium oxide (Nd2O3) nano-crystalline powders at atmospheric (1 Atm) and vacuum (0.03 mbar) pressures. We synthesized the rare-earth oxide nano-crystalline powders by thermal decomposition technique. The crystal structure and morphological properties were determined by X-Ray Diffraction (XRD) and high-resolution transmission electron microscope (HRTEM). The optical region emission spectra of rare earth oxide powders measured in the 400–900 nm wavelength region at 1 atm and 0.03 mbar pressure. Luminescence spectra upon 808 nm, and/or 975 nm diode laser excitation were carried out at room temperature. The white light (WL) emission properties, color quality parameters were investigated at atmospheric and vacuum pressures. Synthesis Procedure We synthesized the rare-earth oxide nano-crystalline powders by thermal decomposition technique. For synthesis, rare-earth nitrate salts were used as precursors. Alginic acid sodium salt was used for gelation [1]. Details on the preparation method were described in some previous works [2, 3]. Results and Discussion Structural and Morphological Properties X-ray diffraction (XRD) patterns were collected by Bruker AXS D8 diffractometer. According to JCPDS (Joint Committee for Powder Diffraction Data), the peak positions observed in the XRD pattern of Yb2O3, Nd2O3, and Er2O3 powders corresponded well with Card# 01-074-1981, Card# 01-070-2152, Card# 01-074-1983, respectively. The peak positions of Nd2O3 powder correspond well with Nd2O2(CO3) crystalline phase is originated from the combination of alginic acid and nitrate salt of neodymium during the synthesis process [3, 4]. The morphological properties were investigated by a Jeol 2100F model high resolution transmission electron microscope (HRTEM). The particle sizes are in good agreement with the results obtained from XRD measurements. Spectroscopic Measurements The optical region emission spectra upon 808 nm, and/or 975 nm diode laser excitation were carried out at room temperature. For vacuum pressure, the samples were mounted in a closed chamber pumped by a vacuum pump. Both at vacuum and atmospheric pressures, bright white light was observed under 808 nm laser excitation for Nd2O3, Er2O3 nano powder, and under 975 nm laser excitation for Yb2O3, Er2O3. We also observed some additional overlapping anti-Stokes type emissions at vacuum pressure. The white emission behavior of Nd2O3 at two different pressures are given as an example in Fig. 1.

Morphology And Luminescence Characteristics of Yttriumdisilicate Doped with Yb3+, Er3+(Ho3+) and Tm3+

1 Marmara University, Department of Mechanical Engineering, Goztepe Campus, 34722, Istanbul, Turkey cboyraz@marmara.edu.tr 2 Marmara University, Department of Physics, Goztepe Campus, 34722, Istanbul, Turkey merdem@marmara.edu.tr 4 Marmara University, Department of Chemistry, Goztepe Campus, 34722, Istanbul, Turkey mekmekci@marmara.edu.tr 4 Marmara University, Department of Physics, Goztepe Campus, 34722, Istanbul, Turkey ctav@marmara.edu.tr 5 Marmara University, Department of Physics Engineering, Maslak Campus, 34469, Istanbul, Turkey gozenl@itu.edu.tr