Linear coupling-related pulse splitting in fiber lasers

We demonstrate a unique pulse-splitting mechanism dominated by the linear coupling between two vector modes in a mode-locked fiber laser using polarization-maintaining fiber. As the linear coupling strength increases, the pulse experiences larger perturbations and manifests as stronger spectral sidebands. Correspondingly, the temporal pedestals possessing a higher intensity become untrapped and eventually evolve into a stable pulse. Such linear coupling-related pulse splitting is ubiquitous both in normal- and anomalous-dispersion regimes, fundamentally differing from that induced by the excessive nonlinear phase shift. Experimental observations fully sustain numerical results and provide a flexible approach to managing the number and energy of vector solitons.