Ricerc@Sapienza

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)]. In our experiments, we report for the first time the formation of a supercontinuum spiral emission (SSE), where the spectral components of the output beam are spatially separated in the far-field emitted at the fiber output.