Space-time excitation creates soliton trains in multimode fibers

In this work, we show that injecting a single space-time-coupled light pulse-beam into a multimode graded-index fiber generates a train of multimode solitons. Space-time couplings excite the spatial modes with distinct temporal profiles. Due to nonlinear interactions, with a properly chosen input power these profiles split into several unique multimode solitons. In the case of a spatially chirped input pulse, two solitons composed of modes $L{P}_{01}$ and $L{P}_{11}$ are formed. In the case of the injection of a space-time optical vortex, characterized by its topological charge $\mathrm{\ell }$, a train composed of $\mathrm{\mid }\mathrm{\ell }\mathrm{\mid }+1$ multimode solitons is generated. Their energy and modal composition are directly determined by the absolute value of the topological charge.