Multicolor luminescence in oxygen-deficient Tb3+;doped calcium aluminogermanate glasses

In this paper, we report on the multicolor luminescence in oxygen-deficient Tb3+-doped calcium aluminogermanate glasses. A simple method was proposed to control oxygen-deficient defects in glasses by adding metal Al instead of the corresponding oxide (Al2O3), resulting in efficient blue and red emissions from Tb3+-undoped glasses with 300 and 380 nm excitation wavelengths, respectively. Moreover, in Tb3+-doped oxygen-deficient glasses, bright three-color (sky-blue, green or yellow, and red) luminescence was observed with 300, 380, and 395 nm excitation wavelengths, respectively. These glasses are useful for the fabrication of white light-emitting diode (LED) lighting.

Three-photon-excited upconversion luminescence of niobium ions doped silicate glass by a femtosecond laser irradiation

We report on the bluish green upconversion luminescence of niobium ions doped silicate glass by a femtosecond laser irradiation. The dependence of the fluorescence intensity on the pump power density of laser indicates that the conversion of infrared irradiation to visible emission is dominated by three-photon excitation process. We suggest that the charge transfer from O-2-to Nb5+ can efficiently contribute to the bluish green emission. The results indicate that transition metal ions without d electrons play an important role in fields of optics when embedded into silicate glass matrix. (C) 2008 Optical Society of America.

Transparent Ni2+-doped silicate glass ceramics for broadband near-infrared emission

Transparent Ni2+-doped MgO-Al2O3-Ga2O3-SiO2-TiO2 glass ceramics were fabricated. The precipitated nanocrystal phase in the glass ceramics was identified by X-ray diffraction and transmission electron microscope. Broadband near-infrared emission centered at 1220 nm with full width at half maximum of about 240 nm and lifetime of about 250 mu s was observed with 980 nm excitation. The longer wavelength emission compared with Ni2+-doped MgAl2O4 crystal was attributed to the low crystal field occupied by Ni2+ in the glass ceramics. The present Ni2+-doped transparent glass ceramics may have potential applications in broadband optical amplifiers. (c) 2007 Elsevier B.V. All rights reserved.

Luminescence properties of bismuth-doped lime silicate glasses

Luminescences from bismuth-doped lime silicate glasses were investigated. Luminescences centered at about 400, 650, and 1300 nm were observed, excited at 280, 532 and 808 nm, respectively. These three luminescence bands arise from three different kinds of bismuth ions in the glasses. The visible luminescences centered at 400 and 650 nm arise from Bi3+, and Bi2+, respectively. The infrared luminescences cover the wavelength range from 1000 to 1600 nm when exited by an 808 nm laser diode. The full width at half maximum (FWHM) of the infrared luminescences is more than 205 urn. The intensity of the infrared luminescence decreases with the increment in CaO content. We suggest that the infrared luminescences might arise from Bi+. Such broadband luminescences indicate that the glasses may be potential candidate material for broadband fiber amplifiers and tunable lasers. (C) 2007 Elsevier B.V. All rights reserved.

Nd3+ doped silicate glass photonic crystal fibres

We report on the fabrication of two kinds of large core area Nd3+ doped silicate glass photonic crystal fibres, and demonstration of the fibre waveguiding properties. The measured minimum loss of one kind of fibres is 2.5 db/m at 660nm. The fibres sustain only a single mode at least over the wavelength range from 660nm to 980nm.

Preparation and optical properties of silicate glasses containing Pd nanoparticles

We report the space selective precipitation of Pd nanoparticles in Pd2+ -doped silicate glass by ultrashort laser pulses irradiation and further annealing. Absorption spectra, transmission electron microscopy, refractive index measurement and Z-scan technique demonstrated that metallic Pd nanoparticles were precipitated in the glass sample after irradiation by an 800-nm femtosecond laser and subsequent annealing at 600 degrees C. We discuss a refractive index change and nonlinear absorption that combines the precipitation of Pd nanoparticles. Crown Copyright (c) 2005 Published by Elsevier B.V. All rights reserved.

Raman spectroscopic investigation of pure and ytterbium-doped rare earth silicate crystals

Raman spectroscopy was used to study the molecular structure of a series of selected rare earth (RE) silicate crystals including Y2SiO5 (YSO), LU2SiO5 (LSO), (Lu0.5Y0.5)(2)SiO5 (LYSO) and their ytterbium-doped samples. Raman spectra show resolved bands below 500 cm(-1) region assigned to the modes of SiO4 and oxygen vibrations. Multiple bands indicate the nonequivalence of the RE-O bonds and the lifting of the degeneracy of the RE ion vibration. Low intensity bands below 500 cm(-1) are an indication of impurities. The (SiO4)(4-) tetrahedra are characterized by bands near 200 cm(-1) which show a separation of the components of nu(4) and nu(2), in the 500-700 cm(-1) region which are attributed to the distorting bending vibration and in the 880-1000 cm(-1) region which are attributed to the symmetric and antisymmetric stretching vibrational modes. The majority of the bands in the 300-610 cm(-1) region of Re2SiO5 were found to arise from vibrations involving both Si and RE ions, indicating that there is considerable mixing of Si displacements with Si-O bending modes and RE-0 stretching modes. The Raman spectra of RE silicate crystals were analyzed in terms of the molecular structure of the crystals, which enabled separation of the bands attributed to distinct vibrational units. Copyright (C) 2007 John Wiley & Sons, Ltd.

Spectral investigation of Yb-doped calcium pyroniobate crystal

Ytterbium-doped calcium pyroniobate single crystal has been grown for the first time. Spectral properties of Yb: Ca2Nb2O7 were investigated by emission and absorption spectra. Its cooperative luminescence and fluorescence lifetime were also studied. Yb ions in Ca2Nb2O7 showed very broad absorption and emission bandwidth and relatively large absorption and emission cross-sections. Along with other optical properties, this Yb-doped crystal would be a potential self-frequency doubling femtosecond laser gain material. (C) 2007 Published by Elsevier B.V.