Investigations on dynamics of isomeric bound multi-pure-quartic solitons in mode-locked fiber laser

Pure-quartic solitons (PQSs) have recently attracted growing research interest due to their energy-width scaling characteristics, which expands the understanding of pure-high-order dispersion solitons in nonlinear systems. Additionally, bound solitons are the most representative manifestations of the particle-like nature of solitons and have inspired numerous light-matter analogies. While previous studies have predominantly focused on bound PQSs with equal time separation, reports on isomeric bound multi-PQSs featuring unequal time separation remain scare. Herein, we numerically investigate the dynamics of isomeric bound multi-PQSs associated with the periodic filter effect in mode-locked fiber laser. By modulating the intra-cavity phase delay to achieve distinct periodic filter properties, we obtained isomeric bound multi-PQSs with temporal creeping, spectral breathing, and time walk-off. Analyses of the time-domain, frequency-domain, and pulse energy characteristics reveal that the periodic variations of bound multi-PQSs are linked to intensity exchange and intra-cavity periodic filter effect. These findings imply that PQS fiber lasers may also serve as promising platforms for manipulating the properties of isomeric bound multi-solitons.