Preparation and properties of Tm-doped SiO<sub>2</sub>-ZrO<sub>2</sub> phase separated optical fibers for use in fiber lasers
Petr Vařák, Jan Mrázek, Wilfried Blanc, Jan Aubrecht, Michal Kamrádek, Ondřej Podrazký
Abstract
Zirconium oxide (ZrO 2 ) is a perspective co-dopant of rare-earth ions in silica fibers for use in fiber lasers. ZrO 2 nanoparticles increase the solubility of rare-earth ions and enhance their luminescence properties. In this paper, we report on the fabrication of Zr-Tm codoped silica fibers using the MCVD method combined with modified solution-doping technique. Several fibers with different dopant concentrations were prepared and their optical properties were studied. It was found that increasing Zr concentration leads to the creation of larger ZrO 2 nanoparticles which causes unwanted attenuation. Optimal Zr concentration was found to be 1 at. %. The fiber with optimal Zr concentration and Tm concentration of 260 ppm exhibited 1.8 µm fluorescence lifetime of 420 ± 10 µs. For the first time in literature, we have demonstrated laser operation in a Zr/Tm-codoped silica fiber. The threshold for laser operation was determined to be 233 mW and the slope efficiency of 72.7% was achieved. MCVD combined with modified solution doping proved to be a feasible method of preparation of Tm-doped SiO 2 -ZrO 2 optical fibers for use in fiber lasers.