As a novel design of large-mode-area fiber, the single trench fiber (STF) providing high higher-order-mode suppression with a large mode area for the fundamental mode shows potential for high-power and high-brightness applications. However, the output power of STFs has remained relatively low over the past decade. In this paper, we first conducted a design process for STFs and determined the optimal ratio of the fiber structural parameters. Following this ratio, we fabricated an ytterbium-doped STF and demonstrated an all-fiberized fiber amplifier. The system achieved an output power of 2.5 kW with an M2 factor of 1.396. To the best of our knowledge, the power of the STF in this study is approximately three times higher than the previous single-mode power record.
