Chromium-doped silica optical fibres : influence of the core composition on the Cr oxidation states and crystal fieldReport as inadecuate




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1 LPMC - Laboratoire de physique de la matière condensée

Abstract : We have made chromium-doped, silica-based preforms and optical fibres by Modified Chemical Vapour Deposition and have studied the influence of the chemical composition of the doped region on the Cr-oxidation states and the spectroscopic properties of the samples. Chromium, introduced initially as Cr3+, is partially or totally oxidized during the fabrication process, and is stabilized in the core of the preforms and fibres as Cr3+ in octahedral coordination, and-or as Cr4+ in distorded tetrahedral coordination Cs. Small concentrations ~1-2 mol% of codopants in silica, such as germanium or aluminium, suffice to promote a particular oxidation state. Particularly, 1 mol % of aluminium stabilizes all present chromium into Cr4+. The ligand field parameters, Dq, B and Dq-B, for Cr3+ and Cr4+ are derived. It is shown that the chromium ions in our samples are in low to intermediate ligand field and that Dq and Dq-B decrease when the aluminium content increases. The absorption cross sections of Cr3+ are similar to that reported in glasses and crystals, whereas Cr4+ has lower values than reference laser materials.





Author: Valérie Felice - Bernard Dussardier - Julian Jones - Gérard Monnom - Daniel Ostrowsky -

Source: https://hal.archives-ouvertes.fr/



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