Erbium and ytterbium co-doped transparent oxyfluoride glass-ceramics optical fibers

摘要

According to the earlier author's papers, the erbium/ytterbium co-doped oxyfluoride glass-ceramics fibers should demonstrate better 1550 nm emission under 488/515/980 nm excitation (the erbium Er~(3+) ion transition ~4I_(13/2)→~4I_(15/2)) than corresponding glass fibers (the batch composition 48SiO_211Al_2O_3-7Na_2CO_3-10CaO-10PbO-12PbF_2-1.5/0.6YbF_3-0.5/0.2ErF_3). Glass fibers provided as a core of standard multimode waveguide (the diameter of 62 μm) have been drawn with the mini-tower to the diameter between 50 μm and 80 μm, then annealed in the two-step regime (580°C/1h - nucleation of nano-crystals; 760°C/15/30 min - nano-crystals growth). This kind of heat treatment ensures the transparent glass-ceramics fibers with the microstructure of homogeneously distributed nano-crystals (lead, erbium and ytterbium enriched cubic fluorite-like crystals and hexagonal PbF_2 crystals) embedded in a glassy host. Their transmission covers the range of 80-90% and seems to be sufficient with respect to their provided limited length (~2m). The luminescence intensity for glass-ceramics fibers at 1530 nm is higher than that of respective glass fibers and the lifetimes of the erbium ion excited state ~4I_(13/2) are of the same order (~5 ms). In that context the glass-ceramics fibers discussed above seem to be promising candidates for cores of fiber lasers at the 1550 nm band.