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KPb 2 Cl 5 :Mn 2+ crystal with sizes of centimeters has been successfully grown by a modified Bridgman method. The electronic spectra of Mn 2+ in the title compound have been measured at different temperatures and compared, revealing that the red emission observed at 10 and 77 K in the spectral range from 500 to 800 nm, which vanishes at room temperature, is associated with the radiation from Pb 2+ ions with adjacent defects whereas the orange-red emission in the spectral range from 530 to 680 nm can be undoubtedly attributed to the spin forbidden transition 4 T 1g ( 4 G) → 6 A 1g ( 6 S) of Mn 2+ . The electronic excitation spectra are interpreted in a strong crystal field scheme with the use of the Tanabe–Sugano diagram. Good agreement with the experimental spectroscopic data is obtained with the use of crystal field splitting parameter 10 Dq = 7902 cm −1 , Racah parameters B = 618 cm −1 , and C = 3549 cm −1 .

Eu2+/Sm3+ co-doped silicate glass was prepared by high temperature melting under reducing atmosphere and the Eu2+/Sm3+ co-doped SrSiO3 transparent glass-ceramics were obtained after heat-treatment. X-ray diffraction (XRD) and Raman spectra confirmed the formation of SrSiO3 nano-crystals in the glass matrix. The photoluminescence excitation (PLE) spectra and photoluminescence (PL) spectra of the samples were measured. A broad emission band from 400 nm to 550 nm due to the 4f65d1 → 4f7 transitions of Eu2+ was observed, as well as several sharp emission peaks at 563 nm, 600 nm, 646 nm and 713 nm ascribed to the 4f → 4f transitions of Sm3+. The luminescence properties of the glass ceramics with different molar ratio of Eu2+/Sm3+ were studied and the corresponding chromaticity coordinates were calculated. The ultraviolet light-emitting diode (UV-LED) excitable glass-ceramics emitting white light were obtained by tuning the relative emission intensity of Eu2+ and Sm3+. The results indicate that the Eu2+/Sm3+ co-doped SrSiO3 transparent glass-ceramics can be used as a potential matrix material for White LED under UV-LED excitation.

The polarized absorption and emission spectra have been measured for the Tm3+ doped NaY(MoO4)2 crystal and spectral parameters have been estimated from the absorption data based on the Judd–Ofelt theory. The effective intensity parameters Ω t eff (t = 2, 4, 6) are 11.67 ×10−20, 2.21 × 10−20, 1.74 × 10−20 cm2, respectively. From the intensity parameters, the radiative transition probabilities, radiative lifetimes, branching ratios and the emission cross-section have been calculated. In comparison with other Tm3+ doped laser crystals, Tm3+:NaY(MoO4)2 crystal has potential as a promising laser crystal.

The single crystal of ZnWO 4 :Ho 3+ was grown by Czochralski technique. The XRD, absorption spectra, fluorescence spectrum are presented, and the Judd–Ofelt (J–O) intensity parameters Ω 2 , Ω 4 , Ω 6 are obtained to be 4.61 × 10 −20 cm 2 , 0.16 × 10 −20 cm 2 , 0.48 × 10 −20 cm 2 , respectively. Calculated radiative transition rate, branching ratios, and radiative lifetime for different transition levels of ZnWO 4 :Ho 3+ crystals are presented. The most intense line correlative with the transition 5 S 2 → 5 I 8 at 543 nm is potentially used for green solid state laser, and the fluorescence lifetime of this energy level is 14.1 μs.

NaLa(WO4)(2):Dy3+ crystals were grown successfully by the Czochraski technique. The Raman, infrared, electronic absorption and emission spectra were measured at room temperature. The Judd-Ofelt theory, extended to anisotropic system, has been applied to evaluate the intensity parameters Omega(t) (t=2, 4, 6), radiative transition rates A, radiative lifetimes tau(R), and fluorescent branching ratios. Although there are several transitions originating in the F-4(9/2) level, a major part of emission intensity is contained in the F-4(9/2) -> 6H(13/2) transition. The stimulated emission cross-sections for this transition were estimated by using the Fochtbauer-Ladenburg method. The luminescence decay curve was also measured at room temperature. The results indicate that NaLa(WO4)(2):Dy3+ may be considered as laser active materials operating near 0.57 mu m. (C) 2006 Elsevier B.V. All rights reserved.

Yb3+ doped SrWO4 crystal has been grown by the Czochralski method. Polarized absorption and emission spectra together with fluorescent decay curve were measured at room temperature. The stimulated emission cross sections of the potential laser transitions were determined using the reciprocity method and the Fuchtbauer-Ladenberg formula. The potential laser gain versus wavelength for the F-2(5/2) ->-> F-2(7/2) transition was also estimated and discussed. This material is a potential candidate for a 1.0 mu m laser media. (C) 2006 Elsevier B.V. All rights reserved.

Holmium doped sodium gadolinium tungstate crystals with sizes of about 020 mm x 40 mm were grown successfully by the Czochralski technique along the (001) orientation. Polarized absorption spectra, fluorescence spectra and fluorescence decay curve of Ho3+-doped NaGd(WO4)(2) have been recorded at room temperature. Based on the Judd-Ofelt theory, three intensity parameters were obtained. The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetimes as well as the branching ratios were calculated. The fluorescence lifetime tau(f) of the S-5(2) level was measured to be 5 mu s. (c) 2006 Elsevier B.V. All rights reserved.

The polarized absorption, emission spectra and the fluorescence decay curve of Er3+ ions in the anisotropic NaY(MoO4)2 crystal were investigated at room temperature, and spectral parameters have been calculated from the absorption data based on the Judd–Ofelt theory. The experimental oscillator strengths for the transitions from the ground state to excited states were compared with the theoretical oscillator strengths calculated from the Judd–Ofelt theory. The emission cross-section and gain cross-section for the π- and σ-spectrum were determined for the 4H13/2 → 4H15/2 transition of special interest for laser application.

The luminescence spectra of the 4 F 3/2 → 4 I 9/2 transition of Nd 3+ ions in a SrWO 4 crystal have been analyzed as a function of pressure at room temperature. Experiments have been performed in a diamond-anvil cell up to 13 GPa. At around 10 GPa some changes in the emission spectra have been observed which are attributed to a structural phase transition of the SrWO 4 matrix. These results are in good agreement with a previous paper, in which in a pure SrWO 4 matrix a scheelite to fergusonite phase transition is found around 10.5 GPa. Moreover, with increasing pressure, the decay curves from the 4 F 3/2 are nonexponential and faster indicating that the energy transfer processes between Nd 3+ ions are important.