Rare earth co-doping for increased the efficiency of resonantly pumped Er-fiber lasers

Rare earth co-doping of erbium with optically inactive ytterbium or lanthanum ions was investigated in silica fibers for resonant pumping of amplifiers and lasers. The co-dopants are optically inactive when pumped at 1475 nm and therefore their main role is to reduce erbium clustering in solution-doped fibers. We have demonstrated increased efficiencies compared to fibers where no co-dopants are used. With this technique, a single mode Er-La fiber with an Er ion concentration of 0.98x1025 ions/m3, exhibited a slope efficiency of 79.6% in a core-pumped master oscillator-power amplifier (MOPA) with a signal wavelength of 1560 nm.