Broadband Ultrafast Tandem Core‐Pumped Yb‐Doped Fiber Amplifier

Efficient power scaling of broadband ultrafast pulses represents a persistent and challenging endeavor in ultrafast fiber laser research. Here, we experimentally and numerically demonstrate a high‐performance tandem core‐pumped Yb‐doped fiber amplifier for efficiently generating sub‐100‐fs pulses. Leveraging the high‐brightness, low‐quantum‐defect pumping scheme, we realize an average output power of 27.7 W at a repetition rate of 171 MHz, with a corresponding slope efficiency of up to 91.2%, and the amplified pulses are compressible to 75 fs. Numerical simulations reveal the crucial roles of nonlinear effects and dynamic gain during nonlinear pulse amplification. Furthermore, we explore the feasibility of directly combining the tandem core‐pumping scheme with gain‐managed nonlinear amplification. Numerical results demonstrate its remarkable potential for direct nonlinear spectral broadening and efficient power scaling of low‐energy narrowband seed pulses, enabling the generation of high‐power near‐transform‐limited ultrafast pulses. These findings provide a promising avenue for the development of high‐power, high‐repetition‐rate, high‐efficiency, and short‐duration ultrafast fiber laser systems.