Manuel Vermillac

Steady photodarkening of thulium alumino-silicate fibers pumped at 1.07 μm: quantitative effect of lanthanum, cerium, and thulium.

By pumping thulium-doped silica-based fibers at 1.07 μm, rapid generation of absorbing centers leads to photoinduced attenuation (PIA). This detrimental effect prevents exploiting laser emissions in the visible and near infrared. We report on the characterization of the PIA versus the fiber core composition, particularly the concentration of thulium (Tm), lanthanum (La), and cerium (Ce) ions. We show that UV emission induced by Tm-Tm energy transfers is the source of photodarkening and that lanthanum and cerium are efficient hardeners against PIA.

Thulium-doped nanoparticles and their properties in silica-based optical fibers

Lasers and amplifiers based on thulium-doped silica fibers require improved spectroscopic properties. In this context, one of the most promising approaches is based on the embedding of thulium ions in nanoparticles of tailored composition and structure. This paper presents various methods used to produce thulium-doped nanoparticles inside silica-based optical fibers. Effects of solution doping method during the elaboration of Modified Chemical Vapor Deposition preform and doping solution composition are studied. A comparison is made between the use of solutions containing LaF3:Tm3+ or YAG:Tm3+ nanoparticles and aluminum-lanthanum-thulium chlorides. Results show that for similar lanthanum content, lanthanum-thulium chlorides doping allows for similar enhancement of 3H4 level of Tm3+ than LaF3:Tm3+ doping. Also, effects of aluminum on 3H4 lifetime enhancement and inhibition of nanoparticle’s formation is discussed.

Molecular dynamics study of rare-earth doped Mg-silicate nanoparticles in vitreous silica: from the preform to the fiber

Formation of rare-earth doped nanoparticles into silica matrix has been modelized by Molecular Dynamics simulations. Preforms with molar composition 0.10MgO–0.90SiO2 and 0.01EuO3/2–0.10MgO–0.89SiO2 have been investigated to have an insight on the structure and chemical composition of the nanoparticles, as well as the rare-earth ions local environment and their clustering. We have finally applied a uniaxal elongation of the rare-earth doped preform in order to mimic the drawing step that changes a preform into a fiber. We present herein first results on the modification of the nanoparticles size distribution.

Photo- and Radio-Darkening in Rare-Earth-Doped Silica-Based Optical Fibers

We study rare-earth-doped optical fibers under laser pumping and/or ionizing radiation conditions, and characterize the photo-and/or radio-darkening phenomena happening through processes depending on fiber composition and experimental conditions.