Buildup dynamics of a pulsating dissipative soliton in an all-normal-dispersion PM Yb-doped fiber laser with a NALM.

A pulsating soliton exists in various passively mode-locked fiber lasers. Versatile categories of pulsating solitons have been investigated in a steady regime. However, the formation dynamics of pulsating solitons have not been fully revealed. Herein, we experimentally captured both single pulsating soliton and two pulsating soliton formation processes in an all-normal-dispersion laser. With the help of the time-stretch dispersion Fourier transform technique, the real-time temporal and spectral evolutions of pulsating solitons, during the buildup process, were investigated. It is found that pulsation directly derives from the background noise. In addition, both types of pulsations experience several characteristic stages, including an unstable -switch, spectral shaping, broadening, oscillating, and narrowing, which might be induced by the transient non-balance between the gain and loss of the cavity. We anticipate that the work in this Letter can improve the understanding of pulsating behaviors and bring new insights into the dynamic phenomenon of nonlinear optical systems.