Structural Soliton Molecules in Spatiotemporal Mode-Locking Yb-Doped Fiber Laser

Structural soliton molecule (SM) operations were observed in a spatiotemporal mode-locking Yb-doped fiber laser based on nonlinear polarization rotation technique. When the pump power was fixed and the waveplates carefully adjusted, various structural SMs were formed, including
$(2+2)$
type SMs with equal and unequal intensity, and
$(2+2+2)$
type SM with alternate intensity. Furthermore, numerical simulations give insight into the fine structure of the structural SMs.