1. v-P2O5 micro-clustering in P-doped silica studied by a first-principles Raman investigationLuigi Giacomazzi, Layla Martin-Samos, Antonino Alessi, A. Boukenter, Youcef Ouerdane, Sylvain Girard, Nicolas Richard, Matjaž Valant, Stefano de Gironcoli, 2019, original scientific article Keywords: silica, POHC, optical fibers, Raman, EPR Published in RUNG: 10.05.2019; Views: 4277; Downloads: 0 This document has many files! More... |
2. Overview of radiation induced point defects in silica-based optical fibersSylvain Girard, Antonino Alessi, Vincenzo De Michele, Youcef Ouerdane, A. Boukenter, Adriana Morana, Nicolas Richard, Philippe Paillet, Marco Cannas, Simonpietro Agnello, Imène Reghioua, Blaz Winkler, Layla Martin-Samos, Luigi Giacomazzi, Diego Di Francesca, Thierry Robin, 2019, review article Keywords: optical fibers, point defects, radiation-induced attenuation, GLPC, NBOHC, STH, ODC, P-doping, Ge-doping, Al-doping Published in RUNG: 09.05.2019; Views: 4173; Downloads: 0 This document has many files! More... |
3. OXYGEN-EXCESS RELATED DEFECTS IN SiO2-BASED MATERIALS: COUPLING THEORY AND EXPERIMENTSBlaž Winkler, 2019, doctoral dissertation Abstract: This work is primarily focused on application of standard first-principle computational approaches to model oxygen excess related point defects in amorphous silica. Atomic models with their respective electronic and optical properties are explored together with some conversion mechanisms between defect models.
The first chapter overviews extensive literature about the already known properties of oxygen related defects. Second chapter briefly introduces main methods that have been used in this research, in particular Density Functional Theory (DFT) as energy and force engine with short description of minimal energy path (MEP) algorithm used for modeling chemical/migration reactions, GW approximation for charged electronic excitations (band structure) and Bethe-Salpeter Equation (BSE) for neutral excitations (optical absorption and excitonic structure including electron hole interaction). The third chapter is devoted to the presentation of results. Thanks to the calculation of optical properties of peroxy bridge (POL), a correlation has been found between structural disorder, specifically dihedral angle dispersion, and low coupling with light, which has been identified as main reason why no clear absorption bands have been assigned to the POL. Structure and stability of some other defects, like interstitial ozone molecule (ozonyl) and dioxasilirane (silicon analogy of dioxirane), have been studied. These defects are usually not considered as most important species, however their calculated formation energies are lower compared to some known defects, which indicates they might be present in silica.
From a detailed study on possible reaction mechanisms, it has been found that ozonyl might be one of the most important intermediate steps for oxygen exchange reactions. Results also show that dioxasilirane can be spontaneously created during the interaction of oxygen with lone pair defects. By exploring different reactions between oxygen and pre-existing oxygen deficiency centers (ODCs), calculations predict two kinds of passivation behaviors: single-barrier reversible mechanisms with the formation of dioxasilirane-like groups, for which the network keeps the memory of the precursory lone pair defects, and single or multiple-barrier mechanisms, for which the network loses its memory, either because of the high reverse barrier or because of a reconstruction.
Final part of this research has been devoted to experimental characterization of the response and tolerance of optical fibers loaded with oxygen under irradiation. These include experiments on commercial fiber along with canonical samples (Optical fibers developed with the intention of studying correlations between different fabrication parameters, dopant/impurity concentration and doping concentrations). Studied fibers also include rare-earth doped fibers. Keywords: Silica, DFT, GW-approximation, Bethe-Salpeter equation, NEB, defect, oxygen, oxygen excess centers, oxygen deficiency centers, optical absorption, optical fibers, radiation induced attenuation. Published in RUNG: 07.05.2019; Views: 5611; Downloads: 209 Full text (13,18 MB) |
4. Radiation Effects on Optical Fibers and Fiber-Based SensorsSylvain Girard, A. Boukenter, Youcef Ouerdane, Nicolas Richard, Philippe Paillet, Layla Martin-Samos, Luigi Giacomazzi, Claude Marcandella, 2015, independent scientific component part or a chapter in a monograph Keywords: Optical Fibers, radiation-induced point defects, dosimetry, ab-initio Published in RUNG: 24.10.2018; Views: 4680; Downloads: 0 This document has many files! More... |
5. Neutron irradiation effects on the structural properties of KU1, KS-4V and I301 silica glassesM. León, Luigi Giacomazzi, Sylvain Girard, Nicolas Richard, P. Martín, Layla Martin-Samos, A. Ibarra, A. Boukenter, Youcef Ouerdane, 2014, original scientific article Keywords: silica, defects, optical fibers, hardening Published in RUNG: 03.10.2018; Views: 4776; Downloads: 0 This document has many files! More... |
6. Coupled theoretical and experimental studies for the radiation hardening of silica-based optical fibersNicolas Richard, Sylvain Girard, Luigi Giacomazzi, Layla Martin-Samos, Diego Di Francesca, C. Marcandella, Antonino Alessi, P. Paillet, S. Agnello, A. Boukenter, Youcef Ouerdane, M. Cannas, R. Boscaino, 2014, original scientific article Keywords: silica, defects, optical fibers, hardening Published in RUNG: 03.10.2018; Views: 4750; Downloads: 0 This document has many files! More... |
7. Gamma and x-ray irradiation effects on different Ge and Ge/F doped optical fibersAntonino Alessi, Sylvain Girard, Imene Reghioua, Mattia Fanetti, Diego Di Francesca, Simonpietro Agnello, Marco Cannas, Claude Marcandella, Layla Martin-Samos, N. Richard, Aziz Boukenter, Youcef Ouerdane, 2015, original scientific article Keywords: optical fibers, Germanium, doping, cathodoluminescence, irradiation effect Published in RUNG: 11.04.2016; Views: 6560; Downloads: 0 This document has many files! More... |