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Neutron irradiation effects on the structural properties of KU1, KS-4V and I301 silica glasses
Youcef Ouerdane, A. Boukenter, A. Ibarra, Layla Martin-Samos, P. Martín, Nicolas Richard, Sylvain Girard, Luigi Giacomazzi, M. León, 2014, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...silica, defects, optical fibers, hardening...
Ključne besede: silica, defects, optical fibers, hardening
Objavljeno: 03.10.2018; Ogledov: 2674; Prenosov: 0
.pdf Polno besedilo (724,27 KB)

Radiation Effects on Optical Fibers and Fiber-Based Sensors
Nicolas Richard, Philippe Paillet, Youcef Ouerdane, A. Boukenter, Sylvain Girard, Layla Martin-Samos, Luigi Giacomazzi, Claude Marcandella, 2015, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Najdeno v: ključnih besedah
Ključne besede: Optical Fibers, radiation-induced point defects, dosimetry, ab-initio
Objavljeno: 24.10.2018; Ogledov: 2620; Prenosov: 0
.pdf Polno besedilo (632,99 KB)

Blaž Winkler, 2019, doktorska disertacija

Opis: 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.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Atomic models with their respective electronic and optical properties are explored together with some conversion... ...of the response and tolerance of optical fibers loaded with oxygen under irradiation. These include...
Ključne besede: Silica, DFT, GW-approximation, Bethe-Salpeter equation, NEB, defect, oxygen, oxygen excess centers, oxygen deficiency centers, optical absorption, optical fibers, radiation induced attenuation.
Objavljeno: 07.05.2019; Ogledov: 2792; Prenosov: 148
.pdf Polno besedilo (13,18 MB)

v-P2O5 micro-clustering in P-doped silica studied by a first-principles Raman investigation
Nicolas Richard, Matjaž Valant, Sylvain Girard, Youcef Ouerdane, A. Boukenter, Antonino Alessi, Layla Martin-Samos, Luigi Giacomazzi, Stefano de Gironcoli, 2019, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...silica, POHC, optical fibers, Raman, EPR...
Ključne besede: silica, POHC, optical fibers, Raman, EPR
Objavljeno: 10.05.2019; Ogledov: 2298; Prenosov: 0
.pdf Polno besedilo (1,94 MB)

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