Pure-quartic noise-like pulse generation and its dynamics in an ultrafast fiber laser.

We report on the dynamical generation of pure-quartic noise-like pulses (NLPs) in an ultrafast fiber laser with a net anomalous fourth-order dispersion (FOD). The pure-quartic NLPs can be characterized by the appearance of spectral sidebands on the smooth broad spectra, which are different from conventional NLPs in a net second-order dispersion regime. Moreover, the spectral widths of pure-quartic NLPs are closely related to the intra-cavity net FOD value. This unique observation of the pure-quartic NLPs and their dynamics is further justified by theoretical simulation results, indicating that the existence of the spectral sidebands mainly arises from the large net FOD value within the laser cavity. These findings will further deepen the understanding of the nonlinear soliton dynamics in ultrafast fiber lasers and provide new avenues for exploring the high-order-dispersion pulse behaviors and their applications.