Gokhan Bilir

Characterization of emission properties of Er3+ ions in TeO2–CdF2–WO3 glasses

TeO(2)-CdF(2)-WO(3) glasses with various compositions and Er(3+) concentrations were prepared by conventional melting method. Their optical properties were studied by measuring the absorption, luminescence spectra and the decay patterns at room temperature. From the optical absorption spectra the Judd-Ofelt parameters (Ω(t)), transition probabilities, branching ratios of various transitions, and radiative lifetimes were calculated. The absorption and emission cross-section spectra of the (4)I(15/2) to (4)I(13/2) transition of erbium were determined. Emission quantum efficiencies and the average critical distance R(0) which provides a measure for the strength of cross relaxation were determined.

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.

Peculiar effects accompanying the production of white light by IR excited nanoparticles

We report some unexpected occurrences that have accompanied our recent discovery of white light emission from infrared light excited doped and nominally un-doped oxide nano-powders.

Enhanced luminescence from Y2O3:Nd3+ nano-powders embedded in a silica glass matrix

Nd3+ doped Y2O3 nano-powders were synthesized using the thermal decomposition method with an average particle size of 10 nm, estimated by XRD and TEM measurements. The nano-powders were inserted into the silica glass matrix during the fabrication of the glasses using the sol–gel method. The obtained samples were characterized both structurally and optically. The TEM images of the Y2O3:Nd3+ nano-powders in the silica glass matrix indicated that the nano-powders were dispersed homogeneously in the glass matrix. The emission spectra of the samples with those of freestanding nano-powders showed that the sharp emission peaks became wider and the Stark levels disappeared after introducing nano-powders into the silica. The decay times of the 4F3/2 level were found to enhance after introducing nano-powders into the silica matrix.

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.

Incandescent Lamp-Like White-Light Emission from Doped and Undoped Oxide Nanopowders

We report the production of a broad band emission (ranging from 400 to 900 nm) following the monochromatic infrared light (803.5 nm) continuous wave excitation of either nominally un-doped or Nd-doped up to 20 % yttrium oxide (Y2O3) nanopowders, Y3Al5O12 (YAG) and Cr3+ doped Gd3Ga5O12 (GGG) nano-crystallites. Our experimental results indicate that such emission feature is (i) a nano-scale phenomenon, (ii) demands a threshold pumping power, (iii) cannot be ascribed to an overlap of sharp emission bands in the un-doped case and, (iv) even if assisted by the dopant presence, is a host matrix-related process. In the case of the Y 2O3-based samples, we demonstrate the possibility to obtain “warm” white light with high efficiency and color rendering index approaching the theoretical limit with an alternative approach. Our experimental results make our white light emission very interesting at both fundamental and applicative levels and may open the way to an alternative route with respect to incandescent lamps.

Fluorescence-Based Studies of Nanoparticles

Fluorescence spectroscopy is particularly adept at uncovering the effects of spatial confinement on the spectral properties of transition metals and rare earth ions that are used as dopant in nano-particles. We have investigated a number of nanocrystal systems, such as YAG (Y2Al5O12) and Yttria (Y2O3) of different sizes doped with Chromium, Praseodymium and Neodymium ions. We have chosen to present the results we have obtained on a particular system, Y 2O3 doped with Neodymium ion at different concentrations and different nano-sizes that may be considered representative of all the systems we have investigated.

Luminescence Properties of NanoscaleY 2 O 3 :Nd 3+ Phosphors

The Y2O3:Nd3+nanophosphors were synthesized for different Nd3+concentrations by thermal decomposition method. Luminescence measurements were performed at room temperature. Dependence of the integrated luminescence intensities on the Nd3+concentration and structural properties were studied.