FABRICATION AND CHARACTERIZATION OF YB3+ER3+ PHOSPHOSILICATE FIBERS FOR LASERS

Fabrication process of efficient Yb3+:Er3+ codoped phosphosilicate fib ers by modified chemical vapor deposition (MCVD) combined with the sol ution doping technique is studied in details. We show that the process can be adapted to incorporate low viscosity phosphate glass and some important issues in the fabrication process are discussed. These inclu de the sensitive presintering pass. We also report on the fabrication of a low loss all-glass double clad Yb3+:Er3+ codoped fiber, We explai n how we evaluate the fibers and discuss the effect of the ytterbium t o erbium concentration ratio on the laser characteristics. Finally we present results of some investigations into the mechanisms which can a ffect the efficiency of the lasers, and show that the detrimental up-c onversion from the metastable level of the erbium ions is dramatically reduced by the presence of the ytterbium ions.