KW Class Fiber Lasers

The double-clad multicore fiber laser has proven to be the most efficient, optically-pumped laser. In Phase I, we have demonstated that phase-locking occurs spontaneously among a group of closely packed single mode fiber lasers configured isometrically ina common cladding. This result suggests that, by using our unique power combining technique developed at PC Photonics Corporation, high power output exceeding 1KW in a high-brightness beam is possible and could potentially reach the 10KW range. ThisPhase II proposal presents a detailed description of the 1KW class laser structure consisting of two isometric rings. The design considerations include the total number of single-mode Yb-doped cores, core index, core spacing, clad dimension, fiber length,pumping configuration, gain distribution, cavity finesse and spectral width of in-fiber Bragg gratings. Although the feasibility of this coherent power-combining concept has been demonstrated, there remain several critical technologies that need to bedeveloped for operating fiber lasers at high power level. Specifically, crucial issues are related to (1) the modal discrimination of various supermodes naturally existing in a phase-locked laser system,(2)power damage threshold of rare-earth doped glass,(3) optical pumping at KW levels without causing catastrophic failure, and (4) thermal fracture and non-linear effects. This Phase II proposal presents our technical approaches to resolve these critical issues, and provides a detailed description of ourwork plan, which contains 11 tasks designed specifically for achieving the objectives of this SBIR. The goal is to estaablish a reliable power-scaling model, which will allow us to generate 1KW high-brightness laser beam from phase-locked fiber laserswithout causing power damage to the cores. A prototype will then be built and functionally tested.