Micro-luminescence study of point defects generated by 10 keV X-ray irradiation in Yb-doped optical fibers.

Abstract : Interest in Ytterbium-doped silicate optical fibers is significant because of their use in high-power fiber lasers. However, these fibers suffer from the optical losses generated during their exposures to energetic irradiations. In the present work, we submitted several Yb-doped samples to different doses of 10 keV X-rays and the induced defects are checked through their optical activities by using a micro- luminescence based set-up. This powerful tool is equipped with a UV laser operating at 325nm. A low power of this probe signal is sufficient enough to record the luminescence spectra over a quiet large spectral domain. The tested optical fibers are analyzed along the diameter of their transverse section with a laser spot size of few micrometers. In these conditions we clearly distinguish the fiber core zone from the cladding one. So the irradiation induced optically active defects are localized and the effects of the co-doping elements, such as aluminium or/and phosphorus can be highlighted.