Spectral periodicity in soliton explosions on a broadband mode-locked Yb fiber laser using time-stretch spectroscopy.

Experimentally, we demonstrate, to the best of our knowledge, the first observation of periodic spectrum changing via soliton explosion in a passively mode-locked fiber laser by a nonlinear polarization evolution. Using time stretch to capture 7220 consecutive single-shot spectra over a 100 µs time window in real time, the soliton explosions appear in a transition between two different mode-locking states. Simultaneous measurements of spectrum and pulse energy at three different output points in the laser cavity show that the soliton explosion's dynamics are related to residual dispersion. This study improves the understanding of pulse formation and evolution in the unstable mode-locking regime of lasers.