Fabrication of high-concentration rare-earth doped optical fibers using chelates

A process which uses rare-earth complexes of 2,2,6,6,-tetramethyl-3,5-heptanedione for uniform incorporation of rare earths in the cores of optical fibers is demonstrated. It is a vapor-phase transport process capable of producing fibers having a rare-earth content of at least 11 wt.% and easily lends itself to incorporation of multiple rare-earth dopants. The process gives high rare-earth concentration with low loss and is readily adaptable to multiple rare-earth doping. High-concentration fibers, 1.0 wt.% Nd₂ O₃, necessary for the double-clad fiber laser configuration with low loss, less than 10 dB/km, have been fabricated and shown to have efficiencies approaching quantum limits when pumping well above threshold