Search

New construction of a silica-based multi-ring profile of Tm3+ doped fiber laser is presented. Optimisation of both multi-ring refractive index profile and active ions distribution towards high beam quality mode propagation is a new approach in developing active fiber constructions. Using a system of layers forming the core allows controlling the dopant profile and, consequently, the emission properties of fiber lasers (power density, beam profile shape etc.). The preform fabricated using MCVD technology is presented. The refractive index profile (Δn = 9·10−3), EPMA-EDS analysis (Tm2O3 and Al2O3 concentration 0.56 and 5.2 wt% respectively), and excited state (3F4) decay time are shown. The double-clad fiber laser based on the Fabry-Perot resonator construction (17/240 μm core/cladding) was used for single-mode laser beam generation at a wavelength of 1938.8 nm (exc. @ 790 nm) with an FWHM bandwidth of 0.17 nm (1.68 W output power, M2x = 1.10, M2y = 1.23). For the optimized gain fiber (25/330 μm core/cladding diameters) length, the laser provided an output power of >5 W with a slope efficiency of ∼26%, determined to the absorbed pump power.

Erbium (Er)-doped barium gallo-germanate (BGG) glasses modified by TiO2have been investigated for near-infrared luminescence applications. Luminescence at 1.5 μm associated to 4I13/2 → 4I15/2transition of Er3+ions has been examined in function of TiO2concentration. Several spectroscopic and near-infrared (NIR) laser parameters for Er3+such as stimulated emission cross-section, luminescence bandwidth and lifetime, quantum efficiency, gain bandwidth and figure of merit were determined based on experiments and theoretical calculations using the Judd-Ofelt framework. Our systematic investigations indicate that Er-doped glass with molar ratio GeO2:TiO2 = 1:2 shows excellent luminescence properties and could be successfully applied to near-infrared broadband optical amplifiers.

In the present work, the transparent oxyfluoride glass-ceramic samples containing GdF3:RE3+(RE = Tb, Eu) nanocrystals (nGCs) were fabricated via controlled heat-treatment of precursor xerogels prepared using a sol-gel method. The formation of GdF3nanocrystalline phase from gadolinium(III) trifluoroacetate was verified based on XRD measurements. The average crystal sizes calculated from Scherrer formula were estimated to ∼10 nm as well as ∼6 nm for Tb3+- and Eu3+-doped samples, respectively. The optical behavior of prepared sol-gel samples was evaluated based on photoluminescence excitation (PLE) and emission spectra (PL) as well as luminescence decay analysis. Obtained samples exhibit the 5D4 → 7FJ(J = 6–3, Tb3+) and the 5D0 → 7FJ(J = 0–4, Eu3+) emission bands recorded within the visible spectral area under excitation at near-UV (393 nm (Eu3+), 351, 369, 378 nm (Tb3+)) as well as middle-UV illumination (273 nm (Gd3+)). Additionally, based on recorded decay curves, the luminescence lifetimes (τm) for the 5D4(Tb3+) and the 5D0(Eu3+) excited states were also evaluated. In general, recorded luminescence spectra and double-exponential character of decay curves for nGCs indicate a successful migration of Tb3+and Eu3+dopant ions from amorphous silicate framework to low-phonon energy GdF3nanocrystal phase.

In this work, lead phosphate glasses doubly doped with Tb3+and Ln3+(Ln = Eu, Sm) ions were prepared. The excitation and emission spectra of lanthanides ions were recorded. The luminescent properties of lead phosphate glasses containing various concentrations of acceptor ions were analyzed. It is observed that luminescence bands corresponding to characteristic transitions of rare earth ions are present on emission spectra measured under direct excitation of Tb3+. From the emission spectra, the Commission Internationale de I'Eclairage (CIE) chromaticity coordinates (x, y) were calculated in relation to potential application studied systems for white LEDs. Luminescence lifetimes were also determined based on decay measurements and discussed in details. In general, the luminescence spectra and luminescence lifetimes depend on the relative concentrations of the optically active dopants.

In the present work the influence of co-doping with ytterbium ions (for 0, 0.5, 1.5, 2.5 wt.% of Yb3+) on physical properties of 8/65/35 PLZT was studied. The ceramic powders were synthesized by the modified sol-gel method, and underwent consolidation by the pressure-less sintering techniques, in Ts=1200°C/6h. Our investigations give a detailed account of the relationships between concentrations of trivalent ytterbium ions in PLZT matrix, on their structure, microstructure, as well as luminescence properties. Near-infrared luminescence spectra at about 1020 nm were registered, which correspond to 2F5/2 - 2F7/2 transition of Yb3+. Based on decay measurements, the luminescence lifetimes for the 2F5/2 excited state of Yb3+ were determined. Luminescence decay analysis indicates that the 2F5/2 lifetime increase with increasing activator concentration (Yb3+) in PLZT ceramic matrix.

In present work, the optical and structural properties of silica sol-gel glasses and glass-ceramic materials singly- and doubly-doped with Eu3+and Gd3+ions were investigated. The optical properties of studied systems were determined based on absorption, excitation and emission spectra as well as luminescence decay analysis. Conducted studies clearly indicated a significant enhancement of visible emission originated from Eu3+ions as a result of changing the excitation mechanism, via Gd3+→Eu3+energy transfer. The luminescence intensity R-ratio was analyzed before and after heat-treatment process upon excitation at γex=393 nm and γex=273 nm. Moreover, the influence of excitation wavelength on luminescence decay time of the 5D0excited state was also analyzed. The Gd3+→Eu3+energy transfer efficiencies for precursor and annealed samples were calculated based on luminescence lifetime of the 6P7/2level of Gd3+ions. The X-ray diffraction measurements were conducted to verify the nature of obtained sol-gel materials. In result, the formation of orthorhombic GdF3nanocrystal phase dispersed in amorphous silica glass host was identified after annealing. Obtained results clearly indicated an incorporation of Eu3+activators into formed GdF3nanocrystals. Thus, conducted heat-treatment process led to considerable changes in surrounding environment around Eu3+ions. Actually, it was found that energy transfer phenomenon and heat-treatment process were responsible for significant improvement of Eu3+luminescence in studied sol-gel samples.

A series of novel, highly phosphorescent cyclometalated iridium(III) complexes of type [(X2C^N)2Ir(Q2bpy)]+PF6–(where X2C^N is 2-phenylpyridine or 2-(2,4-difluorophenyl)pyridine anion and Q2bpy are 4,4′-bifunctionalized 2,2′-bipyridines) is presented. The complexes were fully characterized by means of NMR spectroscopy, high-resolution mass spectrometry (HRMS), cyclic voltammetry, and UV–vis. For several compounds also the crystallographic structures were obtained. The cyclometalates exhibited efficient photoluminescence at 298 K both in solution and in the solid state with good intensity and color purity. The emission wavelength range covered almost the whole visible spectrum and was strongly correlated with the EWG/ERG character of the Q substituent in the ancillary ligand. For further insight into the electronic structure of the complexes, a comprehensive electrochemical support (CV) was introduced, and finally, it was confronted with theoretical background using a density functional theory approach together with time-dependent calculations of the excited states.

GdF_3 nanocrystals doped with Eu^3+ ions in oxyfluoride glass ceramics were prepared by a solgel method. The structural properties were examined by x-ray diffraction measurements. The effects of gadolinium codoping on europium emission in the prepared solgel glasses and glass ceramics have been studied. The emission bands originating from the D_05 state of Eu^3+ ions are enhanced under excitation of Gd^3+ ions by 273 nm line. The electric dipole D_05→F_27 transitions were dominant in the samples before heat treatment, whereas magnetic dipole D_05→F_17 transitions had a higher probability in the samples after annealing. The luminescence lifetime for the D_05 level of Eu^3+ ions in the samples after excitation at 273 nm is long lived in comparison to excitation at 393 nm and increased to 190%. Energy transfer from Gd^3+ to Eu^3+ was observed.

In the present work the influence of neodymium concentration (0-1at-%) and sintering conditions on 8/65/35 PLZT:Nd3+ ceramics were studied. All ceramic powders were synthesized by MOM technique from high purity raw materials (>99,9%), and subsequently sintered by free sintering and hot uniaxial pressing method. To analyze the powders and ceramics more the XRD, EDS SEM, and ferroelectric measurements were performed. Optical spectra were examined for all prepared samples, and their optical properties were analyzed using reflectance, excitation and luminescence measurements. The study gives a detailed account of the relationships between doping and preparing conditions on the basic physical and dielectric and optical properties of obtained ceramic materials.

Dy‐doped borate glasses with PbO and PbX2(X = F, Cl) were examined using Raman and luminescence spectroscopy. The Raman spectra show the structural changes of a glass network with B2O3/PbO ratios and presence of PbX2(X = F or Cl). The photoluminescence spectra measured in the visible range present two bands located at 480 and 573 nm, which correspond to 4F9/2–6H15/2(blue) and 4F9/2–6H13/2(yellow) transitions of Dy3+. Luminescence decays from the 4F9/2state and yellow/blue luminescence intensity ratios (Y/B) were analyzed as a function of glass composition (B2O3/PbO) and PbX2(X = F, Cl) content. The branching ratios of yellow/blue luminescence increase, whereas the 4F9/2lifetime of Dy3+ions decreases with increasing PbO concentration. An introduction of PbX2to the borate glass results in the increasing of 4F9/2lifetime and decreasing of the yellow‐to‐blue luminescence intensity ratio. These phenomena are related to reduction of covalency between Dy3+and O2−/X−ions.

Heavy metal oxide and oxyhalide glasses containing Er3+ions have been investigated. Near-infrared luminescence at about 1550 nm and up-conversion spectra of Er3+ions were registered under excitation by 980 nm diode laser line. Several luminescence bands are observed, which correspond to the 4I13/2- 4I15/2(1550 nm), 2H11/2,4S3/2- 4I15/2(550 nm), 4F9/2- 4I15/2(670 nm) and 4I9/2- 4I15/2(800 nm) transitions of Er3+, respectively. The optical transitions of Er3+ions have been examined as a function of glass host and PbX2(X = F, Cl, Br) content.

Lead phosphate glasses containing rare earth ions were prepared in a glow box in order to minimize concentration of hydroxyl groups. Rare earths as an optically active ions were limited to Eu3+, Dy3+, Tb3+and Er3+. Luminescence of rare earth ions in lead phosphate glasses was registered in visible spectral region. Luminescence bands correspond to 5D0- 7FJ(J = 0 ÷ 4) transitions of Eu3+ions, 4F9/2- 6HJ/2(J = 11, 13, 15) transitions of Dy3+ions, 5D3- 7FJ'(J' = 1 ÷ 6) and 5D4- 7FJ(J = 3 ÷ 6) transitions of Tb3+ions, and 4S3/2- 4I15/2transitions of Er3+ ions, respectively. Luminescence decays from excited states of rare earth ions have been analyzed in details.

Selected oxyfluoride glasses containing Eu3+and Dy3+were heat treated in order to obtain transparent glass-ceramics. Visible emission spectra corresponding to 5D0- 7FJ(J = 0, 1, 2, 3, 4) transitions of Eu3+and 4F9/2- 6HJ/2(J = 11, 13, 15) transitions of Dy3+in glass samples before and after heat treatment were registered. The luminescence intensity ratios R (Eu3+) and Y/B (Dy3+) have been analyzed in details. Their values are reduced due to part incorporation of rare earth ions into cubic -PbF2crystalline phase.

Selected heavy metal glasses containing Yb3+and Er3+ions have been investigated. Near-infrared luminescence spectra at 1.53 m and up-conversion spectra of Er3+were registered under excitation of Yb3+by 975 nm diode laser line. The luminescence bands correspond to 4I13/2- 4I15/2(NIR), 4S3/2- 4I15/2(green) and 4F9/2- 4I15/2(red) transitions of Er3+, respectively. The optical transitions of rare earth ions have been examined as a function of glass host.

Selected oxyfluoroborate glasses have been investigated before and after heat treatment. Transparent glass-ceramics (TGC) were obtained during controlled crystallization (devitrification). X-ray diffraction studies confirmed that material was partially crystallized. Diffraction lines due to orthorhombic PbF2 phase were identified for heat-treated samples at various temperatures and times. Results were compared to that ones obtained for as-melted glass.

Lead lanthanum zirconate titanate (known as PLZT) ceramic powders have been prepared by the modified sol – gel method, and underwent consolidation by the hot uniaxial pressing method. Application of such technique of preparation permitted to receive fine-grained transparent PLZT x/65/35 ceramics, with x = 8 -10 La at.%. The present publication gives a detailed account of the relationships between technology and physical properties of obtained materials. To analyze all ceramics SEM, EDS and mercury porosimetry were performed, and dielectric properties were studied too. Quite wide light transparency from the visible to nearinfrared range for PLZT ceramics was detected using optical absorption and infrared spectroscopy.

In the present work the influence of neodymium concentration (0-1at-%) and sintering conditions on 8/65/35 PLZT:Nd3+ ceramics were studied. All ceramic powders were synthesized by MOM technique from high purity raw materials (>99,9%), and subsequently sintered by free sintering and hot uniaxial pressing method. To analyze the powders and ceramics more the XRD, EDS SEM, and ferroelectric measurements were performed. Optical spectra were examined for all prepared samples, and their optical properties were analyzed using reflectance, excitation and luminescence measurements. The study gives a detailed account of the relationships between doping and preparing conditions on the basic physical and dielectric and optical properties of obtained ceramic materials.

In the present work the influence of co-doping with ytterbium ions (for 0, 0.5, 1.5, 2.5 wt.% of Yb3+) on physical properties of 8/65/35 PLZT was studied. The ceramic powders were synthesized by the modified sol-gel method, and underwent consolidation by the pressure-less sintering techniques, in Ts=1200°C/6h. Our investigations give a detailed account of the relationships between concentrations of trivalent ytterbium ions in PLZT matrix, on their structure, microstructure, as well as luminescence properties. Near-infrared luminescence spectra at about 1020 nm were registered, which correspond to 2F5/2 - 2F7/2 transition of Yb3+. Based on decay measurements, the luminescence lifetimes for the 2F5/2 excited state of Yb3+ were determined. Luminescence decay analysis indicates that the 2F5/2 lifetime increase with increasing activator concentration (Yb3+) in PLZT ceramic matrix.

Lead lanthanum zirconate titanate (known as PLZT) ceramic powders have been prepared by the modified sol – gel method, and underwent consolidation by the hot uniaxial pressing method. Application of such technique of preparation permitted to receive fine-grained transparent PLZT x/65/35 ceramics, with x = 8 -10 La at.%. The present publication gives a detailed account of the relationships between technology and physical properties of obtained materials. To analyze all ceramics SEM, EDS and mercury porosimetry were performed, and dielectric properties were studied too. Quite wide light transparency from the visible to nearinfrared range for PLZT ceramics was detected using optical absorption and infrared spectroscopy.

The mechanism of the initiation step of -lactones polymerization with potassium anions of alkalide is verified, as had been suggested by Szwarc Szwarc, M. Ionic Polymerization Fundamentals; Carl Hanser Verlag:  Munich, 1996; p 69. Contrary to previous papers, the carbon−carbon bond scission is not observed. It is shown that indeed this kind of bond rupture does not occur, at least in -butyrolactone. In fact, the acyl−oxygen bond is mainly cleaved in this lactone by potassium anions. The reaction proceeds by lactone dianion as an intermediate succeeding formation of the radical anion. The latter decomposes by the alkyl−oxygen bond cleavage in a side reaction. Finally, potassium crotonate and potassium 3-hydroxybutyrate are mainly formed, and potassium butyrate is a side product. They become the real initiators of the polymerization. The same results are observed with alkalide K-, K(15-crown-5)2, and K-,K(18-crown-6).

The objective of this review is to outline the photochemical, electrochemical, and enzymatic methods that are currently used for ether-bond cleavage. Key results have been extracted from publications covering the past 15 years of research activity in this field. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Lead phosphate glasses containing Eu^3+ and Dy^3+ have been studied. Local structure was verified using Fourier transform (FT)-IR spectroscopy. Emission bands of Eu^3+ and Dy^3+ ions in lead phosphate glasses are observed in the visible spectral range, which correspond to D_05?F_J7 (J=0,1,2,4) and F_9/24?H_J/26 (J=15,13,11) transitions, respectively. Shorter luminescence decays from excited states of Eu^3+ and Dy^3+ are due to the presence of PbO in phosphate glass.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.