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

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 Er3+ ion transition I-4(13/2) -> I-4(15/2)) than corresponding glass fibers (the batch composition 48SiO(2)11Al(2)O(3)-7Na(2)CO(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 mu m) have been drawn with the mini-tower to the diameter between 50 mu m and 80 mu m, then annealed in the two-step regime (580 degrees C/1h-nucleation of nano-crystals; 760 degrees 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 PbF2 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 (similar to 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 I-4(13/2) are of the same order (similar to 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.