Generation of sub-50 fs, multi-microjoule laser pulses with divided pulse nonlinear amplification.

In this paper, we demonstrate a high-power Yb-doped fiber femtosecond laser system integrating divided-pulse amplification (DPA) with pre-chirped management amplification (PCMA). The PCM-DPA system generates 42 fs pulses with 5.1 μJ energy at 10.2 MHz repetition rate spanning from 980 to 1100 nm. Birefringent crystal-based temporal division resolves the limitation of the self-focusing threshold. The innovative interferometric recombination provides flexible and precise adjustment in the phase difference of pulse replicas, while ensuring stable and efficient output with recombination efficiency of 75%. To our knowledge, this work establishes the highest-energy sub-50 fs pulses directly produced from a nonlinear fiber amplifier. The PCM-DPA technique represents a major advancement in high-power, high-repetition-rate femtosecond laser sources, enabling new possibilities in strong-field and ultrafast applications demanding simultaneous high photon flux and ultrashort pulse duration.