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

Valérie Felice (1) , Bernard Dussardier (1) , Julian K. Jones (1) , Gérard Monnom (1) , Daniel B. Ostrowsky (1)

1 LPMC - Laboratoire de physique de la matière condensée

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.

Domaines: Optique [physics.optics]

Valérie Felice, Bernard Dussardier, Julian K. Jones, Gérard Monnom, Daniel B. Ostrowsky. Chromium-doped silica optical fibres : influence of the core composition on the Cr oxidation states and crystal field. Optical Materials, 2001, 16, pp.269-277. ⟨hal-00469711⟩