Dissipative soliton generation in Yb-fiber laser with an invisible intracavity bandpass filter

We report on dissipative soliton (DS) generation in an Yb-doped (YDF) fiber laser passively mode locked with the nonlinear polarization rotation (NPR) technique. We found that even without the insertion of a physical bandpass filter in the cavity, not only could DSs be automatically formed in the laser but also the formed DSs have a spectral bandwidth that is far narrower than the Yb-fiber gain bandwidth. Numerical simulations well reproduced the experimental observations. Our results suggest that a physical intracavity bandpass filter is not a crucial component for the generation of DSs in all-normal-dispersion YDF lasers mode locked with the NPR technique.