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Radiation Effects on Silica-Based Preforms and Optical Fibers-II: Coupling Ab initio Simulations and Experiments

Abstract : Abstract—Experimental characterization through electron paramagnetic resonance (EPR) and confocal luminescence microscopy (CML) of a Ge-doped glass (preform and fiber) reveals the generation of several point defects by 10 keV X-ray radiation-induced attenuation: GeE', Ge(1), Ge(2), and Ge-ODC. The generation mechanisms of Ge-ODC and charged defects like GeE' centers are studied through ab initio simulation. Our calculations used a 108 atom supercell with a glass composition comparable to the Ge-doped core or to the pure-silica cladding of the canonical sample. The large size of our cell allows us to study the influence of the local environment surrounding the X-ODC defect (X = Si or Ge) on its structure parameters (e.g., Si-X bond length) and its energy of formation. We found a statistical correlation between these two characteristics for pure- and Ge-doped silica-based glasses suggesting that the Si-ODC and Ge-ODC will be preferentially generated at sites leading to the shortest Si-X distances. We also evaluated the possible influence of the local environments of the defect on their generation mechanisms. From the whole set of possible X-ODC in the amorphous cells, we calculated the charged structures that can be obtained through the removing of one electron of the cell. For pure-silica glass, about 80% of the oxygen vacancies lead to a dimer structure and 20% to puckered ones. For the doped glass, the percentage of the final dimer structures is reduced to 42% while the puckered charged percentage increases to 36%. We also note the appearance of 22% of divalent centers. Further simulation shows that the presence of the Ge inside the glass strongly affects the generation mechanisms of Si-related centers.
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Contributor : Youcef Ouerdane <>
Submitted on : Thursday, January 22, 2009 - 6:07:32 PM
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Sébastien Girard, N. Richard, Y. Ouerdane, G. Origlio, A. Boukenter, et al.. Radiation Effects on Silica-Based Preforms and Optical Fibers-II: Coupling Ab initio Simulations and Experiments. IEEE Transactions on Nuclear Science, Institute of Electrical and Electronics Engineers, 2008, 55 (6), pp.3508-3514. ⟨10.1109/TNS.2008.2007232⟩. ⟨ujm-00355495⟩



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