New Material Strengthens High-Power Fiber Lasers Published Feb. 8, 2013 By Dr. Robert Nelson Materials and Manufacturing 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.