An optical fiber preform made of highly doped terbium oxide (Tb2O3) aluminosilicate glass. This high Verdet constant material is then drawn into optical fibers. (AFRL Image) Cross section of the manufactured isolator fiber. (AFRL Image) New Material Strengthens High-Power Fiber Lasers by Dr. Robert Nelson Materials and Manufacturing 2/8/2013 - WRIGHT-PATTERSON AIR FORCE BASE -- AdValue Photonics, Inc., under a contract with The Air Force Research Laboratory, designed and fabricated heavily terbium doped glass resulting in the manufacturing of magneto-optic fibers with core diameters from 4 micron to 10 micron. The terbium doped fibers allow for the production of an all-fiber high-energy laser (HEL) by providing the missing HEL component: the rugged, all-fiber optical isolator. The new magneto-optic fibers exhibit a large magnetooptic Verdet constant of -32rad/Tm and show low optical losses. This enables manufacturing of efficient, all-fiber optical isolators for high-energy fiber lasers, used in a wide range of new industry and military defense applications. Significant progress developing high-power fiber lasers has been made the last several years. Despite the successful deployment of these applications, a need for the all-fiber optical isolator, a critical all-fiber, high-energy laser system component remained. Optical isolators absorb harmful back-traveling reflections within optical systems, and high-power back-traveling reflections can harm components on the back end of a laser system. The power limit of current fiber-coupled isolators at approximately 20W is two orders of magnitude too low. Previous to the manufacturing of the new magneto-optic fibers, free-space isolators were used but considered an unsatisfactory solution. Free-space isolators require fiber termination, precise lens and component alignment, and a difficult recoupling of high-energy laser back into small single-mode optical fibers. It is unrealistic to use free-space isolators as a long-term solution for tactical high energy fiber lasers because a free-space isolator loses the primary advantages of ruggedness and high reliability with repeated use. A more robust isolator for all-fiber high energy laser systems was required, and the manufacture of magneto-optic fibers made its production possible. This new technology provides a more robust and cost-efficient solution than free-space isolators.