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Structure of Er3+-doped SiO2-HfO2 Glass and Glass-Ceramic Planar Waveguides using EXAFS and XRD

Francesco Rocca
2008
2008
Istituto di fotonica e nanotecnologie - IFN
ESRF User Meeting 2008
No
Grenoble (Francia)
Abstract: Er3+-doped SiO2 glasses represent the basic material used in the fabrication of photonics devices such as optical amplifiers. Having binary or ternary glassy hosts can lead to systems with better spectroscopic properties, compared to the basic SiO2 glass. Introducing additional oxides is an attempt to enhance the limited solubility of the rare-earth ion. Another motivation is trying to alter the crystal field around these ions. Recently, this procedure has been extended to growing nanocrystalline phases of the co-dopant oxide, obtaining new materials where rare-earth ions are present in small nanocrystals dispersed in the host glass. Many co-dopant oxides such as Na2O, TiO2, and Al2O3 have been reported in literature, leading in most cases to improvement in the properties. Here we present results of introducing HfO2 into the Er3+-doped SiO2 glassy system. Both the glassy and glass-ceramic regimes were covered in this study. Planar waveguides with the nominal compositions 1 mol % Er3+-doped (1-x)SiO2-xHfO2 (x = 0:0; 0:9; 1:8; 5; 8; 10; 20; 30; 40; and 50 mol %) were prepared by the sol-gel route and dip-coated on amorphous SiO2 substrates. All the samples were thermally annealed at 900oC for duration depend-ing on HfO2 content, obtaining fully densified amorphous waveguides. Nanocrystals of HfO2 were successively grown by appropriate further thermal annealing. The structure of the glass and glass-ceramic waveguides was characterized by XRD and both Er and Hf L3-edges EXAFS measurements carried on ESRF Beamlines. In the glassy regime, our EXAFS results at Er L3-edge show the strong tendency of Er3+ ions to be present in HfO2-rich regions for HfO2 concentration ¸ 5 mol %, without altering its local structure between 10 and 50 mol % HfO2. These results were confirmed by both Photoluminescence (PL) and Raman results. At lower concentrations of HfO2, the local structure around Er3+ is modified with respect to the pure SiO2 host. In the glass-ceramic regime, even with 5 mol % HfO2, it was possible to grow HfO2 nanocrystals. Both Hf L3-edge EXAFS and XRD results evidence the substitution of Hf by Er ions in the nanocrystals. Er L3-edge EXAFS results clearly show an ordered environment around the rare-earth ion. This environment is sensitive to the size of HfO2 nanocrystals, which in turn is tunable by controlling the heat treatment. These findings were found coherent with the measured PL spectra. Very similar results were obtained on waveguides fabricated by the RF-sputtering technique.
3
none
D Afify, Nasser; Dalba, Giuseppe; Rocca, Francesco
273
info:eu-repo/semantics/conferenceObject
04 Contributo in convegno::04.01 Contributo in Atti di convegno
04.01 Contributo in Atti di convegno
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/76134
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