Generation and interaction force analysis of loosely bound state soliton in passively mode-locked fiber laser

In this paper, the loosely bound state pulses are obtained in a passively mode-locked Er-doped fiber laser (EDFL). The microfiber-based two-dimensional In2Se3 nanosheets with a low modulation depth of ∼0.48% is chosen as the saturable absorber (SA), which is beneficial to generate bound state soliton. When the pump power increases from 83 to 450 mW, the number of the bound state soliton varies from 16 to 337, which can be attributed to the balance between the attraction from the dispersive wave (DW) and the repulsion from the gain-absorption depletion and recovery (GADR). Moreover, a subsequent theoretical simulation is also carried out to further demonstrate the experimental phenomena. In addition, the internal dynamics of pulse generation is deeply studied, which is of great significance for further understanding the bound state pulses.