5 kW power-level 1050 nm narrow-linewidth fiber amplifier enabled by biconical-tapered active fiber

• Pengfei Ma, Zhiyong Pan, Tianfu Yao, Huan Yang, Yisha Chen, Wei Liu, Xiaolin Wang, Zefeng Wang, Pu Zhou, and Jinbao Chen
• received 04/05/2024; accepted 04/25/2024; posted 04/26/2024; Doc. ID 525777
• Abstract: Effective wavelength expansion is vital in the applications of high-power narrow-linewidth fiber lasers. In this work, we demonstrate a 5-kW power-level narrow-linewidth fiber amplifier at 1050 nm utilizing a homemade biconical-tapered Yb-doped fiber (BT-YDF) as active fiber. Up to ~4.96 kW fiber laser is achieved with the 3 dB spectral linewidth of ~0.54 nm and the beam quality factor of Mx2=1.46, My2=1.6. The experimental comparisons reveal the advantages of BT-YDF in improving stimulated Raman scattering threshold and balancing transverse mode instability suppression of the fiber amplifier at 1050 nm. This work could provide a well reference to extend the operating wavelength of high-power YDFAs.