Structures and generation mechanisms of paramagnetic centers and absorption bands responsible for Ge-doped SiO2 optical-fiber gratings

Makoto Fujimaki, Tomofumi Watanabe, Tetsuya Katoh, Toshiaki Kasahara, Nahoko Miyazaki, Yoshimichi Ohki, Hiroyuki Nishikawa

    Research output: Contribution to journalArticle

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    Abstract

    Paramagnetic centers and absorption bands induced by ultraviolet photons in Ge-doped SiO2 glass are investigated. Four kinds of samples with different Ge contents were exposed to ultraviolet photons from a KrF excimer laser (5.0 eV), a XeCl excimer lamp (4.0 eV), and a KrCl excimer lamp (5.6 eV). Irradiation with the KrF excimer laser induces two paramagnetic centers, named Ge(1) and Ge(2), in proportion with a decrease in the absorption at 5.1 eV and with an increase in absorption at 4.5 and 5.8 eV. The total density of the induced paramagnetic centers is linearly proportional to each induced change of the three absorption components and their proportionality constants are independent of the Ge content of the samples. The 4.0-eV photons from the XeCl excimer lamp induce only a Ge E′ center, while the 5.6-eV photons from the KrCl excimer lamp induce a Ge(1) besides a Ge E′ center. From these results, Ge(1) and Ge(2) are, respectively, assigned to the Ge electron center (GEC) and the positively charged Ge oxygen-deficient center (GODC)+, which donated an electron to the GEC. The oscillator strength of the GODC for the absorption at 5.1 eV was found to be 0.1. From this, it is considered that the GODC that acts as the electron donor is the Ge lone pair center (GLPC). Thermally stimulated luminescence (TSL) is also examined in Ge-doped SiO2 glass that was exposed to photons from the KrF excimer laser. The TSL spectrum is very similar to the photoluminescence spectrum that is known to be due to the GLPC's. It was found that the absorption, which was induced by the KrF excimer laser photons, decreases during the TSL measurement and that this decrement of the absorption is proportional to the TSL intensity. As mentioned above, the electrons that are to be trapped to generate the GEC's are released from the GLPC's during the photon irradiation. Then, in its reverse reaction, these electrons are thermally detrapped from the GEC's to regenerate the GLPC's, and the TSL is caused by an electronic de-excitation in such formed GLPC's. To conclude, the TSL phenomenon further validates the assumption that the GLPC is the electron donor to generate the GEC's.

    Original languageEnglish
    Pages (from-to)3920-3926
    Number of pages7
    JournalPhysical Review B - Condensed Matter and Materials Physics
    Volume57
    Issue number7
    Publication statusPublished - 1998 Feb 15

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    Optical fibers
    Absorption spectra
    Photons
    optical fibers
    Luminescence
    gratings
    absorption spectra
    Excimer lasers
    Electrons
    Electric lamps
    excimers
    luminescence
    photons
    excimer lasers
    luminaires
    Oxygen
    electrons
    Irradiation
    Glass
    oxygen

    ASJC Scopus subject areas

    • Condensed Matter Physics

    Cite this

    Structures and generation mechanisms of paramagnetic centers and absorption bands responsible for Ge-doped SiO2 optical-fiber gratings. / Fujimaki, Makoto; Watanabe, Tomofumi; Katoh, Tetsuya; Kasahara, Toshiaki; Miyazaki, Nahoko; Ohki, Yoshimichi; Nishikawa, Hiroyuki.

    In: Physical Review B - Condensed Matter and Materials Physics, Vol. 57, No. 7, 15.02.1998, p. 3920-3926.

    Research output: Contribution to journalArticle

    Fujimaki, Makoto ; Watanabe, Tomofumi ; Katoh, Tetsuya ; Kasahara, Toshiaki ; Miyazaki, Nahoko ; Ohki, Yoshimichi ; Nishikawa, Hiroyuki. / Structures and generation mechanisms of paramagnetic centers and absorption bands responsible for Ge-doped SiO2 optical-fiber gratings. In: Physical Review B - Condensed Matter and Materials Physics. 1998 ; Vol. 57, No. 7. pp. 3920-3926.
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    abstract = "Paramagnetic centers and absorption bands induced by ultraviolet photons in Ge-doped SiO2 glass are investigated. Four kinds of samples with different Ge contents were exposed to ultraviolet photons from a KrF excimer laser (5.0 eV), a XeCl excimer lamp (4.0 eV), and a KrCl excimer lamp (5.6 eV). Irradiation with the KrF excimer laser induces two paramagnetic centers, named Ge(1) and Ge(2), in proportion with a decrease in the absorption at 5.1 eV and with an increase in absorption at 4.5 and 5.8 eV. The total density of the induced paramagnetic centers is linearly proportional to each induced change of the three absorption components and their proportionality constants are independent of the Ge content of the samples. The 4.0-eV photons from the XeCl excimer lamp induce only a Ge E′ center, while the 5.6-eV photons from the KrCl excimer lamp induce a Ge(1) besides a Ge E′ center. From these results, Ge(1) and Ge(2) are, respectively, assigned to the Ge electron center (GEC) and the positively charged Ge oxygen-deficient center (GODC)+, which donated an electron to the GEC. The oscillator strength of the GODC for the absorption at 5.1 eV was found to be 0.1. From this, it is considered that the GODC that acts as the electron donor is the Ge lone pair center (GLPC). Thermally stimulated luminescence (TSL) is also examined in Ge-doped SiO2 glass that was exposed to photons from the KrF excimer laser. The TSL spectrum is very similar to the photoluminescence spectrum that is known to be due to the GLPC's. It was found that the absorption, which was induced by the KrF excimer laser photons, decreases during the TSL measurement and that this decrement of the absorption is proportional to the TSL intensity. As mentioned above, the electrons that are to be trapped to generate the GEC's are released from the GLPC's during the photon irradiation. Then, in its reverse reaction, these electrons are thermally detrapped from the GEC's to regenerate the GLPC's, and the TSL is caused by an electronic de-excitation in such formed GLPC's. To conclude, the TSL phenomenon further validates the assumption that the GLPC is the electron donor to generate the GEC's.",
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    AU - Katoh, Tetsuya

    AU - Kasahara, Toshiaki

    AU - Miyazaki, Nahoko

    AU - Ohki, Yoshimichi

    AU - Nishikawa, Hiroyuki

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    N2 - Paramagnetic centers and absorption bands induced by ultraviolet photons in Ge-doped SiO2 glass are investigated. Four kinds of samples with different Ge contents were exposed to ultraviolet photons from a KrF excimer laser (5.0 eV), a XeCl excimer lamp (4.0 eV), and a KrCl excimer lamp (5.6 eV). Irradiation with the KrF excimer laser induces two paramagnetic centers, named Ge(1) and Ge(2), in proportion with a decrease in the absorption at 5.1 eV and with an increase in absorption at 4.5 and 5.8 eV. The total density of the induced paramagnetic centers is linearly proportional to each induced change of the three absorption components and their proportionality constants are independent of the Ge content of the samples. The 4.0-eV photons from the XeCl excimer lamp induce only a Ge E′ center, while the 5.6-eV photons from the KrCl excimer lamp induce a Ge(1) besides a Ge E′ center. From these results, Ge(1) and Ge(2) are, respectively, assigned to the Ge electron center (GEC) and the positively charged Ge oxygen-deficient center (GODC)+, which donated an electron to the GEC. The oscillator strength of the GODC for the absorption at 5.1 eV was found to be 0.1. From this, it is considered that the GODC that acts as the electron donor is the Ge lone pair center (GLPC). Thermally stimulated luminescence (TSL) is also examined in Ge-doped SiO2 glass that was exposed to photons from the KrF excimer laser. The TSL spectrum is very similar to the photoluminescence spectrum that is known to be due to the GLPC's. It was found that the absorption, which was induced by the KrF excimer laser photons, decreases during the TSL measurement and that this decrement of the absorption is proportional to the TSL intensity. As mentioned above, the electrons that are to be trapped to generate the GEC's are released from the GLPC's during the photon irradiation. Then, in its reverse reaction, these electrons are thermally detrapped from the GEC's to regenerate the GLPC's, and the TSL is caused by an electronic de-excitation in such formed GLPC's. To conclude, the TSL phenomenon further validates the assumption that the GLPC is the electron donor to generate the GEC's.

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