Revealing the Dynamics of Multiple Solitons and Soliton Pulsations in a Quartic‐Dispersion Fiber Laser

Abstract In the realm of ultrafast fiber lasers, emerging pure‐quartic solitons (PQSs) have attracted considerable attention owing to their unique energy‐width scaling advantage, fundamentally different from conventional second‐order dispersion solitons, and can offer unprecedented energy scaling‐up capabilities. In this paper, the complex PQS dynamics involving various soliton states, including multiple pure‐quartic solitons (MPQSs) and pulsating PQSs are observed and investigated in a passively mode‐locked fiber laser with net quartic dispersions. These underlying PQS dynamical phenomena are attributed to the interplay between the dominated fourth‐order dispersion and nonlinear effects. In the MPQS regime, several PQSs coexist in a single bunch, where the pulse separations between each other fall in the range of several hundreds of picoseconds. These PQS bunches can be termed as loosely‐bounded PQS solitons. In addition, the pulsating PQSs, manifesting periodic intensity oscillations accompanied with a variable pulse energy, are also observed. Their formation and evolution are susceptible to the pump power level, which is verified by the numerical simulations. These results can provide in‐depth insights into the intricate nonlinear dynamics of high‐order‐dispersion solitons within dissipative optical systems and the performance improvement of ultrafast fiber lasers in practical applications.