Numerical study on the continuous-wave Yb-doped fiber amplifiers operating near 980 nm

In this paper, the properties of continuous-wave Yb-doped fiber amplifiers operating near 980 nm are investigated numerically. The effects of the seed light, active fiber configuration, pump power, pumping scheme and residual reflectivity of output port on performance of the 980-nm amplifier are revealed. It is found that besides the core-to-cladding ratio, both the seed power and pump power should large enough to realize the high output efficiency. It is also revealed that although the core-to-cladding ratio is important for the output power and efficiency, it only has a negligible effect on the optimum length of Yb-doped fiber. It is found that the optimum length is almost uniquely determined by the dopant concentration of Yb-doped fiber, and the plus of these two parameters are a constant almost unvaried with other parameters of Yb-doped fiber. With this result, a simple but effective method for estimating the optimum length of Yb-doped fiber is presented. Besides, it is also found that the residual reflectivity of output port should be no larger than 10−5 to optimize the output property of the 980-nm fiber amplifier. We believe that the pertinent results can provide significant guidance for deeply understanding and designing the 980-nm Yb-doped fiber amplifier.