Pulsating pure-quartic solitons with spectral asymmetry in an ultrafast fiber laser

In this work, we report the first experimental generation and observation of pure-quartic soliton (PQS) pulsations with spectral asymmetry in an ultrafast fiber laser. In addition to the asymmetric spectral sidebands, a unique feature of these observed pulsating PQSs lies in that the pulsation periods are fairly stable for varying net fourth-order dispersion (FOD) values and pump powers. Moreover, the pulsating PQSs exhibit a maximum average output power of ~22.16 mW, corresponding to a pulse energy of ~2.34 nJ. Finally, numerical simulations have been performed, which are in good agreement with the experimental results. These findings not only reveal a new dynamic regime of PQSs but also provide critical insights into the underlying mechanisms governing their formation and stability, further laying a foundational framework for the future development of high-energy PQS fiber lasers and contributing to a broader understanding of soliton dynamics driven by higher-order dispersion effects.