Navegando por Palavras-chave "color centers"

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    Confocal and atomic force microscopies of color centers produced by ultrashort laser irradiation in LiF crystals
    (Amer Inst Physics, 2008-01-01) Courrol, Lilia Coronato [UNIFESP]; Martinez, Oscar; Samad, Ricardo Elgul; Gomes, Laercio; Ranieri, Izilda Marcia; Baldochi, Sonia Licia; Freitas, Anderson Zanardi de; Vieira Junior, Nilson Dias; Wetter, N. U.; Frejlich, J.; Universidade Federal de São Paulo (UNIFESP)
    We report properties of the spatial and spectral distribution of color centers produced in LiF single crystals by ultrashort high intensity laser pulses (60 fs, 10 GW) using confocal spectral microscopy and atomic force microscopy. We could identify a large amount of F centers that gave rise to aggregates such as F-2, F-4, F-2(+) and F-3(+) distributed in cracked shape brownish areas. We have taken a 3D image using confocal microscopy of the sample (luminescent image) and no difference is observed in the different planes. The atomic force microscopy image clearly shows the presence of defects on the modified surface. The formation of micrometer or sub-micrometer voids, filaments and void strings was observed and related to filamentation process.
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    Study of color centers produced in thulium doped YLF crystals irradiated by electron beam and femtosecond laser pulses
    (Elsevier B.V., 2007-02-15) Courrol, Lilia C.; Ranieri, Izilda M.; Baldochi, Sonia Licia; Samad, Ricardo E.; Freitas, Anderson Z. de; Gomes, Laercio; Vieira, Nilson D.; Universidade Federal de São Paulo (UNIFESP); IPEN
    In this work, we report the influence of the presence of photochromic and color centers in the photobleaching of thulium ions blue emission in YLF (YLiF4) crystals doped with 1 mol% Tm (3+). the samples were irradiated at room temperature both with electron beam and high intensity ultrashort pulses from a Ti:Sapphire CPA laser system. in both irradiations the production of photochromic and color centers was observed via the absorption bands in the UV and visible ranges. Pure LiF and pure and oxygen doped YLF crystals were used to identify the color centers produced and their optical properties. From a phenomenological model it was possible to study the interaction between color centers and thulium ions, and their effect in photobleaching and photodarkening behaviors. Finally, the blue up laser level population was computed using a rate equation analysis. (c) 2006 Elsevier B.V. All rights reserved.