Buildup dynamics in an all-polarization-maintaining Yb-doped fiber laser mode-locked by nonlinear polarization evolution

Soliton buildup dynamics in ultrafast fiber lasers are one of the most significant topics in both the fundamental and industrial fields. In this work, by using the dispersive Fourier transformation technique, the real-time spectral evolution of soliton buildup dynamics were investigated in the all-polarization-maintaining Yb-doped fiber laser, which is mode-locked by nonlinear polarization evolution technique through the cross splicing method. It was experimentally confirmed that the same stable soliton state could be achieved through different soliton starting processes because of the initial random noises. In one case, the maximum pulse energy during the soliton starting process could reach ∼15 times the stable pulse energy, which results in the spectral chaotic state and temporal shift. We also provide another soliton buildup case with the same cavity parameters, which illustrates more moderate evolution. It involves smaller energy variation and no complex transition state. These results would deepen our understanding of soliton buildup dynamics and be beneficial for the applications of ultrafast fiber lasers.