Ricerc@Sapienza

In recent years, nonlinear pulse propagation in multimode fibers (MMFs) is has experienced a dramatic resurgence of interest, because of their potential for opti- cal communications and high-power lasers. However, from the fundamental view- point several aspects still remain to be fully understood. Here we experimentally and theoretically studied the dynamics of high-energy (up to reaching the fiber damage threshold) spatiotemporal solitons in MMFs with a graded-index (GRIN) core profile.

In this work, we reveal that when using femtosecond pump pulses, one has access to a different regime, where the peak power inside the MM fiber may reach and even surpass the critical power Pcr for catastrophic self-focusing (this is about 10 MW in fused- silica). When these peak power levels are reached, the propagating light beam undergoes a so-called filamentation phenomenon, leading to the so-called conical emission (CE)].