Patent ID: 8494013

Claim:
An optical fiber lasing medium comprising: a core portion formed from silica-based glass comprising a rare-earth dopant and deuterium, the core portion having an index of refraction n c , a numerical aperture NA c , and a concentration of defect color centers of less than 1×10 16 /cm 3 , wherein the deuterium is combined with the defect color centers to form reacted defect color centers and the reacted defect color centers do not absorb ultraviolet and visible wavelengths of light; and a first cladding portion formed from silica-based glass, the first cladding portion surrounding and directly contacting the core portion and having an index of refraction n 1 , wherein the index of refraction n 1 of the first cladding portion is less than the index of refraction n c of the core portion.