The incorporation of a new approach, gain-guiding, into high power fiber laser engineering will allow much larger mode diameters in fibers, leading to greatly increased single-mode signal powers, and substantial gain discrimination in favor of single-mode operation. The impact of this development could be as significant as the introduction of double cladding was several years ago. It will effectively increase the effective core diameter of single-mode fiber lasers thereby lessen the pump-power restrictions of diode lasers, and provide a pathway to the development of fiber lasers, lessening the deleterious impact of nonlinear effects as well as the power restrictions on the diode pump laser. Gain-guiding will require the fabrication of special fibers, in which a radially varying doping density extends over a diameter as large as several hundred microns. In the first phase of this development, we will demonstrate the increased mode size that comes from including gain guiding in a small fiber laser of intermediate power. Special fibers with radially varying doping will be acquired through collaboration with a state-of-the-art fiber research facility. A firm foundation will thus be created for the development of Kilowatt-class fiber lasers using gain-guiding in the second phase of this project.
