Observation of diverse structural bound-state patterns in a passively mode-locked fiber laser

We report on the observation of diverse structural bound-state patterns in a fiber laser mode-locked by nonlinear polarization rotation. By boosting the pump power, the bound states with fixed soliton separation are observed, where the soliton number inside the bound states increases from two solitons to fourteen solitons. Apart from the aforementioned bound states with regular triangular autocorrelation envelopes, the bound states with compound soliton structure are also obtained, typically including the (2+2)-type, (2+2+2)-type, (2+1)-type, and (3+1)-type bound states. Additionally, numerical simulations are also implemented to confirm fine structure of the bound states.