M.G. Brik

White light emission from Sm3+/Tb3+ codoped oxyfluoride aluminosilicate glasses under UV light excitation

In this paper, we report on the absorption and photoluminescence properties of oxyfluoride aluminosilicate and boro-aluminosilicate glasses codoped with Sm3+ and Tb3+ ions. The differential thermal analysis profiles of these glasses have been obtained to confirm their thermal stability. From the measured absorption spectrum, Judd?Ofelt (J?O) intensity parameters (?2, ?4 and ?6) have been evaluated for the Sm3+ ion. When excited by ultraviolet light these glasses emit a combination of blue, green and orange?red wavelengths forming white light. The ratio of the intensities of orange?red to green emissions can be tuned by varying both the concentration of the Sm3+ ion and the composition of the glass matrix. The excitation and emission spectra have shown a self-quenching effect for the Sm3+ ions and an efficient energy transfer from Tb3+?:?5D4 ? Sm3+?:?4G5/2 was observed which was also confirmed by the decay lifetime measurements.

Photoluminescence of Eu3+-, Tb3+-, Dy3+- and Tm3+-doped transparent GeO2–TiO2–K2O glass ceramics

In this paper, we present the photoluminescence properties of Eu3+-, Tb3+-, Dy3+- and Tm3+-doped potassium–titanium–germanate glasses and glass ceramics. Following the x-ray diffraction measurement, the glass structure was established. Compared to Eu3+-, Tb3+-, Dy3+- and Tm3+-doped glasses, their respective glass ceramics show stronger emissions due to the presence of the K2TiGe3O9 crystalline phase. For Eu3+-doped glass and glass ceramics, five emission bands centered at 578 nm , 592 nm , 614 nm , 653 nm and 702 nm have been observed with 394 nm excitation wavelength. Of them, 614 nm has shown a bright reddish-orange emission. For Tb3+-doped glass and glass ceramic, four emission bands centered at 490 nm , 549 nm , 586 nm and 621 nm have been observed with an excitation at 378 nm wavelength. Of them, 549 nm has shown a bright green emission. With regard to Dy3+:glass and glass ceramic, a blue emission band centered at 485 nm and a bright fluorescent yellow emission at 576 nm have been observed, apart from (665 nm) emission transition with an excitation at 387 nm , 4F7/2) wavelength. Emission bands of (650 nm) and (700 nm) transitions for the Tm3+:glass and glass ceramic, with excitation at (468 nm), have been observed. The stimulated emission cross sections of all the emission bands of Eu3+, Tb3+, Dy3+ and Tm3+:glasses and glass ceramics have been computed based on their measured Δλ (FWHM) and lifetimes (τm).

Synthesis and optical properties of infrared-emitting YF3:Nd nanoparticles

Nd3+-doped YF3 (YF3:Nd) nanoparticles with a size of ∼20 nm were synthesized by solvothermal decomposition of yttrium and neodymium trifluoroacetate precursors in oleylamine. Using the 4f-energy matrix diagonalization procedure various interaction parameters: Slater–Condon (F2, F4, and F6), spin-orbit (ξ), two body interaction (α, β, and γ), Judd parameters (T2, T3, T4, T6, T7, and T8), spin-other-orbit parameters (M0, M2, and M4) and electrostatically correlated spin-orbit interaction parameters (P2, P4, and P6), and the crystal-field parameters (Bqk) were evaluated. The potential of YF3:Nd as a laser host for 1052 nm emission was evaluated by quantitative analysis of the absorption, emission spectra, and fluorescence decay characteristics. Judd–Ofelt parametrization was employed to compute the radiative spectral parameters such as radiative transition probabilities, fluorescence branching ratios, stimulated emission cross sections, and quantum efficiencies of the observed bands in the fluorescence spect...

Lanthanide Compounds with Fluorinated Aryloxide Ligands : Near-Infrared Emission from Nd, Tm, and Er

Ln(OC(6)F(5))(3) form stable, isolable compounds with 1,2-dimethoxyethane (DME). Monomeric (DME)(2)Ln(OC(6)F(5))(3) (Ln = Nd, Er, Tm) adopt seven coordinate structures with two chelating DME and three terminal phenoxide ligands. Both (py)(4)Er(OC(6)F(5))(3) and (THF)(3)Yb(OC(6)F(5))(3) were also prepared and structurally characterized, with the latter being a mer-octahedral compound with bond lengths that are geometry dependent. Emission experiments on crystalline powders of the Nd(III), Tm(III), and Er(III) DME derivatives show that these compounds are highly emissive near-infrared sources.

Electronic structure of Ce3+ multicenters in yttrium aluminum garnets

Low temperature, infrared, and visible-ultraviolet absorption spectra of yttrium aluminum garnet (YAG) bulk crystals and epitaxial layers doped with Ce are presented. In the region of intra-configurational 4f–4f transitions, the spectra of the bulk YAG crystals exhibit existence of at least two different Ce3+ related centers, a major one associated with Ce in regular positions substituting yttrium and also additional center, due to so called antisite positions in the garnet host, i.e., ions in the Al positions. Crystal field analysis based on exchange charge model exhibit excellent agreement with the experimental data for major Ce3+ center.

Spectroscopic and crystal field studies of YAlO(3) single crystals doped with Mn ions.

Detailed analysis of the spectroscopic properties of the YAlO(3) crystals doped with manganese ions has been performed. The exchange charge model of the crystal field was used to calculate the crystal field parameters and energy levels of the Mn(4+) and Mn(5+) ions in YAlO(3). It was shown that both ions contribute to the formation of the absorption spectra. The calculated energy levels are in good agreement with the main observed absorption peaks. Comparison of the Racah parameters B for both ions in YAlO(3) with those for free ions shows a significant role played by the covalent effects, especially for Mn(5+).

Spectral and fluorescent kinetics features of Nd3+ ion in Nb2O5, Ta2O5 and La2O3 mixed lithium zirconium silicate glasses.

Li(2)O-ZrO(2)-SiO(2):Nd(3+) glasses mixed with Nb(2)O(5), Ta(2)O(5) and La(2)O(3) were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature. The Judd-Ofelt theory was successfully applied to characterize Nd(3+) spectra of all the three glasses. From this theory, various radiative properties like transition probability A, branching ratio β(r), the radiative lifetime τ(r), for (4)F(3/2) emission level in the spectra of these glasses has been evaluated. The radiative life time for (4)F(3/2) level of Nd(3+) ions has also been measured and quantum efficiencies were estimated. Among the three glasses studied, the La(2)O(3) mixed glass has exhibited the highest quantum efficiency. The reasons for such higher value have been discussed based on the relationship between the structural modifications taking place around the Nd(3+) ions.

Influence of Tm+3 concentration on the non-linear optical effects of the BiB3O6 : Tm3+ glass nanoparticle-doped polymer

It is shown that BiB3O6 : Tm3+ glass nanoparticles incorporated into polymethylmethacrylate (PMMA) and polycarbonate (PC) polymer matrices show good second-order susceptibilities under bicolour coherent laser treatment. It is found that only during incorporation into highly polarized PC matrices could one observe an enhancement of the second-order susceptibilities with increasing laser treated power densities. The main increase is observed for all samples at power densities equal to about 0.4 GW cm−2. After passing this value there is a saturation of the output susceptibilities and even an abrupt decrease. The most striking feature is the achievement of second-order susceptibilities equal to about 5 pm V−1 for samples containing 4% nanoparticle (NP) content in the PC matrix. A further increase in the NP concentration to 6% leads to a decrease in susceptibility to 15%. In the case of PMMA matrices these changes do not exceed the background. The same situation is present for the pure BIBO and low-doped Tm materials. The effect is maximal for a low concentration of Tm—about 0.75%. In the case of bulk glasses the intensity dependences of the second-harmonic generation unambiguously show that the achieved maximal values of second-order susceptibilities do not exceed 3 pm V−1 for 0.5% Tm concentration.

Low symmetry aspects in spectroscopic and magnetic susceptibility studies of Tb3+(4f8) in TbAlO3

The three sets of crystal field parameters (CFPs) obtained from spectroscopic and magnetic susceptibility studies of Tb3+(4i*) ions in TbA1O3 by Gruber et al. (J. Lumin. 128 (2008) 1271) were reanalyzed. These sets, fitted from experimental energy levels, are physically equivalent and correspond to specific choices of the axis system. Proper interpretation of experimental data for Tb3+ ions at monoclimc Cs symmetry sites in TbA1O3 crystal requires clarification of several intricate low symmetry aspects, namely, (a) three equivalent forms of monoclinic CF Hamiltonian, (b) relative orientation of the crystallographic axis system w.r.t. the symmetry-adapted axis system, (c) mono-clinic standardization of CFPs, (d) distinction between the actual and apparent low symmetry effects exhibited by CFPs, and (e) nominal nature of all fitted CFP sets. For this purpose, modeling of CFPs for Tb3+ in TbA1O3 was carried out using at the first stage only the Coulomb, i.e. point charge, contributions in the exchange charge model. The point charge model calculated CFPs disagree with the experimental CFPs, especially the rank k=6 CFPs. To explain this discrepancy and to verify the correctness of the theoretical CFP calculations additionally the superposition model was employed. The methods of analysis and modeling of CFP sets for monoclinic symmetry cases proposed here proved useful for the studied case as well as might be used for other ion-host systems exhibiting monoclinic or triclinic local site symmetry. Partial results for Tb3+ ions in TbA1O3 were presented here, whereas detailed results were given in a follow-up paper.

Structural, electronic, and optical features of CuAl(S(1-x)Se(x))2 solar cell materials

Detailed first-principles calculations of the structural, electronic, and optical properties of solid solutions of the promising solar cell material CuAl(S(1-x)Se(x))2 over the whole range of Se concentration from x = 0 to x = 1 were performed. It was established that the calculated lattice parameters, band gap, and anisotropic refractive indices vary linearly with the Se concentration. The obtained linear dependences allow for reliable estimations of all these quantities for any value of x, which determines the solid solution composition. The calculated results were compared with the experimental data available for x = 0, 0.5, and 1.0; very good agreement was demonstrated, which gives confidence in the properties calculated for other Se concentrations (x = 0.25, 0.75). The findings from the present paper can be used in a straightforward way for the successful production of CuAl(S(1-x)Se(x))2 mixed compounds with desired optoelectronic parameters, which are defined by the composition-tuned mobility of the charge carriers in the upper valence band and the conduction band. Extension of the presented approach to other materials is also possible.