High-Power, Diode Pumped, Eye-Safe Fiber Lasers/Amplifiers

Low-cost, high-power diode pumped fiber lasers emitting at eye-safe wavelengths have a very large market in both commercial and military arenas. High-power double-cladded fiber lasers which emit at 1.06 microns are now available. To develop high-power, eye-safe fiber lasers such as Er-doped fiber lasers involving a three-level interaction, the key problem, which must be addressed, is the relatively low pumping efficiency of these rare-earth ions residing in a very small core region as compared with the four-level Nd-doped or quasi-four-level Yb-doped laser systems. In Phase I, a detailed investigation of three new double-cladded fiber structures which are designed and configured to enhance the pumping efficiency is proposed. In addition, we propose the use of Yb:Er codoping to form the core. Configurations to be explored include (1) a corrugated inner cladding, (2) enlarged doping profile, and (3) a multicore fiber bundle. The Phase I effort will be focused on the development of scalable models, which can provide quantitative results on the performance of these lasers and their limitations. By using these models involving new double-cladded Yb:Er-codoped fibers, an optimum design of a low-cost, diode-pumped, high-power fiber laser oscillating at an eye-safe wavelength will be established. Based on this optimum design, a prototype will be built, demonstrated and evaluated in Phase II.