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Photo-noircissement dans les fibres optiques dopées au thulium pompées à 1,07 µm

Thèse Jean-François LUPI

à 14h en salle C. Brot

This thesis, conducted at the Laboratoire de Physique de la Matière Condensée (LPMC), is in the context of new lasers and optical fibre amplifiers operating in the visible. This wavelength range is currently booming for many applications. However, the development of such fibres are limited by the photo-darkening phenomenon. This phenomenon consists of the loss of transparency in the material during its use under optical pumping. This thesis is devoted to the study and the resolution of issues caused by photo-darkening in aluminium- and thulium-doped silica optical fibres when optically pumped at 1.07 µm. In this thesis, a new method of fibre manufacture that is specific to our needs has been developed and implemented at LPMC. A systematic study of the role of thulium concentration in the photo-darkening mechanism was conducted. The role of the co-doping with aluminum, cerium or lanthanum was also analyzed by systematic studies. The photo-darkening is attributed to the generation of color centers by pumping. Once created, these color centers can be bleached by the pump. A phenomenological model of the dynamics of photo-darkening allows a separate discussion between the generation and the bleaching phenomena. In this work, it is shown that the increasing of the concentration of thulium and/or the pump power has the effect of increasing the generation phenomenon. In opposite, increasing of the concentration of aluminum or cerium or lanthanum has the effect to intensify the bleaching mechanism. The identification and understanding of these mechanisms open the path to new lasers and optical fiber amplifiers in the visible range.