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750-W double-clad ytterbium tapered fiber laser with nearly theoretically limited efficiency

We report the theoretical and experimental study of the properties of an active tapered double clad fiber (T-DCF). Optimization of the most important parameters of T-DCF such as tapering ratio, longitudinal profile, core/clad ratio and absorption have been considered. Using optimized T-DCF design we have demonstrated a high-power (750W) and highly efficient (80%) ytterbium fiber laser.