Alternate anti-phase pulsation in a mode-locked Yb-doped fiber laser

Pulsations have been widely studied in mode-locked fiber lasers because their behavior is analogous to oscillations in other dissipative systems. Despite extensive research on various pulsations, a detailed investigation into pulsations originating from the periodic evolution of pulse polarization states remains absent. We report the experimental observation of an alternate anti-phase pulsation (AAP) in a mode-locked Yb-doped fiber laser. AAP exhibits periodic anti-phase intensity oscillations between adjacent pulses. Dispersive Fourier transform measurements reveal that the temporal AAP corresponds to synchronized, periodic spectral variations in the frequency domain. The pulsation period depends on the net cavity dispersion. Additionally, the amplitude of the AAP decreases as the laser transitions from single-pulse to multi-pulse bound states. The mechanism of the AAP is considered to arise from the periodic evolution of the polarization state between adjacent pulses. These findings provide crucial insights into the role of vector mechanisms in complex pulse behaviors and offer guidance for designing advanced laser systems.