## Abstract

In this paper, the impact of the loss of high-order mode (HOM) on the performances of high-power fiber amplifiers (HPFA) has been numerically investigated by using the model considering transverse spatial-hole burning. The HPFA is modeled with various parameters such as pump wavelength, pumping direction, and fiber length. The fact that the output power of HOM will decrease with increasing loss of HOM is explained by the numerical analysis for the first time to the best of our knowledge. Moreover, the results show that the extracted efficiency of the amplifier will decrease dramatically with increasing HOM loss when the loss is low. The efficiency will increase smoothly and finally converge, as the growth of the HOM loss in the regime where the efficiency crosses the minimum. The evolution of the output power of HOM and the efficiency can be attributed to the interaction between the loss and the nonuniformly distributed local gain, which will be clearly illustrated by simulations. We believe the results will be beneficial to understanding the impact of the loss of HOM on the amplifier performances and providing guidelines on designing large-mode-area fiber and optimizing the HPFA aiming at effective single-mode output based on differential loss between the HOMs and the fundamental mode.

© 2016 Optical Society of America

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