Photodarkening resistant optical fibers and fiber lasers incorporating the same

A fiber laser system comprising:

• a pump laser;
• an optical fiber lasing medium optically coupled to the pump laser, the 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 nc, a numerical aperture NAc, and a concentration of defect color centers of less than 1×1016/cm3, 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 n1, wherein the index of refraction n1 of the first cladding portion is less than the index of refraction nc of the core portion;
• and
• a containment chamber positioned around and spaced apart from at least a portion of the first cladding portion, wherein the optical fiber lasing medium is sealed in the containment chamber and the containment chamber is filled with a gaseous atmosphere comprising deuterium.

A method for manufacturing optical fiber lasing media, the method comprising:

• forming a core preform portion of an optical fiber preform such that the core preform portion comprises an active rare earth dopant;
• forming a first cladding preform portion of the optical fiber preform such that the first cladding preform portion is positioned around and in direct contact with the core preform portion;
• consolidating the optical fiber preform such that an optical fiber drawn from the optical fiber preform has a concentration of defect color centers of less than 1×1016/cm3;
• drawing the optical fiber preform into an optical fiber;
• and
• positioning the optical fiber in a soaking chamber having a gaseous atmosphere comprising helium and deuterium gas, wherein the deuterium gas reacts with the defect color centers to form reacted defect color centers that do not absorb ultraviolet and visible wavelengths of light.