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Nanocrystalline powders of Eu3+doped Gd3Ga3Al2O12(GGAG) were prepared using modified Pechini method. The nanocrystals with the size from tens to hundreds nanometres were obtained. For growth of single crystal GGAG:Eu the Czochralski method was utilized. The crystal structure, grains morphology and optical properties of GAGG doped with different concentration of Eu3+ and calcined at different temperatures were investigated and discussed. The impact of grain size and Eu3+concentration on the spectroscopic properties of Gd3Ga3Al2O12:Eu3+was checked and analyzed. The spectroscopic properties of the nanopowders were compared to the Gd3Ga3Al2O12:Eu3+single crystal. The influence of effective index of refraction was taken into account in the analysis of transition rates of metastable multiplet and it was found that grain size (surface area) of the nanocrystals has huge impact on the luminescence decay time

The Czochralski growth of Dy3+-doped (Lu1−xGdx)2SiO5solid solution single crystals with different mixtures of Lu2SiO5and Gd2SiO5oxides (x= 0, 0.2, 0.4, 0.6, 0.8, and 1) is reported. It was found that the (Lu1−xGdx)2SiO5crystals retain structural, physical, and optical properties of Lu2SiO5even for x= 0.8. Optical investigation of Dy:(Lu1−xGdx)2SiO5revealed that the structural disorder of the host brings about a strong inhomogeneous broadening of Dy3+spectral bands while influencing weakly rates of its radiative and nonradiative transitions. Dielectric characteristics of solid solution crystals are presented and discussed. Finally, (Lu1−xGdx)2SiO5solid solution crystals seem to be an attractive alternative to a Lu2SiO5host for the design of novel phosphors, radiation converters, and lasers owing to a significantly lower melting temperature and hence easier and less expensive manufacturing.

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.

Vacuum ultraviolet, visible, and infrared luminescence of Nd 3+incorporated into hexafluorocryolite-type K 3YF 6lattice were investigated. Emission from the 4f 25d 1at 8 K is observed after the excitation of 4f 25d 1by synchrotron radiation. At higher temperatures only the transitions within the 4f shell are observed with the significant participation of 2G(2) 9/2emission to the lower 4f levels. The difference between near-infrared emission spectra excited at 800 and 186 nm implies that emission band excited at 186 nm consists of overlapping transitions originating from the 4F 3/2and higher energy levels. The room temperature 4F 3/2emission lifetime and the influence of different concentration of Nd 3+ions on rate of the self-quenching luminescence lifetime have been studied in details. The 4F 3/2emission lifetime measured at 2.6 × 10 19/cm 3Nd 3+concentration in K 3YF 6equals 5.3 ms and is the highest value ever reported for Nd 3+-doped crystals.

Two compounds of Eu^II with benzo-18-crown-6, triaqua(benzo-18-crown-6)europium(II) diperchlorate (1) and triaqua(benzo-18-crown-6)europium(II) perchlorate hydrate benzo-18-crown-6 solvate (2), were synthesized by electrochemical reduction. The coordination environment of the metal cation in both cases contains six O atoms of the crown ligand and three water molecules. The first complex display strong blue luminescence with a maximum at 425 nm. The excitation spectra do not show any significant energy transfer from the benzo rings to europium. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

We observed two ultrabroadband near-infrared (NIR) luminescence bands around 1.2 and 1.5?μm in as-grown bismuth-doped CsI halide crystals, without additional aftertreatment. Dependence of the NIR emission properties on the excitation wavelength and measurement temperature was studied. Two kinds of NIR active centers of subvalent bismuth and color centers were demonstrated to coexist in Bi:CsI crystal. The eye-safe 1.5?μm emission band with an FWHM of 140?nm and lifetime of 213?μs at room temperature makes Bi:CsI crystal promising in the applications of the ultrafast laser and ultrabroadband amplifier.

Optical spectra and luminescence decay curves were measured for thulium-doped YVO_4, GdVO_4, and LuVO_4 single crystals as a function of temperature in the 300–670K temperature region. In spite of structural similarity, the three systems studied display significantly different transition intensities and nonradiative relaxation rates. It was found, in particular, that the peak value of the pump band absorption intensity diminishes by about 30% for Tm:YVO_4 and Tm:GdVO_4, and the effective emission cross section for the laser transition of Tm^3+ diminishes by a factor of 2 roughly when temperature increases from 300 to 500K. An unusually small quantum efficiency of the upper laser level in Tm:LuVO_4 has been derived from the analysis of luminescence decay curves.

High optical quality Nd-doped Sc_2SiO_5 crystal with size of diameter 27 mm×60 mm was obtained by Czochralski method. An x-ray diffraction pattern of Nd:SSO crystal confirmed that the as-grown crystal was isostructual with the SSO crystal. Absorption and emission spectra were recorded at 10 K. The Judd-Ofelt theory was applied to obtain standard parameters Ωt(t=2,4,6) and the fitting result of experimental absorption line strengths, which provided the F3/24 radiative lifetime (τ_rad) of 219 μs and the luminescence branching ratio β of 0.57 for the ^4F_3/2-^4I_9/2 laser transition. The stimulated emission cross section of 1.04×10^−19 cm^2 at 1074 nm was calculated using the Füchtbauer-Ladenburg equation. The ^4F_3/2 luminescence lifetimes with 215 μs at 10 K and 198 μs at 300 K were determined from luminescence decay curves, indicating high quantum efficiency in the Nd:SSO crystal. All these results showed that Nd:SSO would be a promising gain media in solid-state lasers.

Optical spectra and luminescence decay curves were measured for erbium-doped YVO_4 and GdVO_4 single crystals as a function of temperature in the 300 K-670 K temperature region. In spite of structural similarity the two systems studied display significantly different transition intensities and nonradiative relaxation rates. It was found in particular that the intensity of parasitic upconverted emission excited at 978 nm depends weakly on temperature for YVO_4:Er^3+, whereas it decreases monotonously with increasing temperature for GdVO_4:Er^3+ and becomes negligibly small at 670 K. It was concluded that GdVO_4:Er^3+ may be a promising laser active material operating at high thermal loading conditions encountered in high-power diode-pumped IR lasers.

We report on photoluminescence studies of Tb^3+ in a polycrystalline cryolite type K_3YF_6 host. The location of the Tb^3+ in the center of inversion forbids the electric-dipole transitions of terbium ions in this material. As a consequence almost the entire luminescence intensity is related to the ^5D4-^7F5 magnetic-dipole transition, and it is contained in the extremely narrow spectral bandwidth amounting to 1.7 nm at 8K and to 18 nm at room temperature. The phosphor under study can be efficiently excited making use of intense f-d transitions of Tb^3+ in the UV-vacuum-UV region and may be of interest for applications requiring high spectral purity of the emission.

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