Experimental observation of spontaneous emission of space-time wavepacket in a multimode optical fiber

TL;DR

This paper combines theory and experiments to observe and analyze the spontaneous formation of a localized space-time wavepacket and its associated broadband intermodal dispersive wave emission in a multimode optical fiber.

Contribution

It provides the first complete analysis linking the formation of a 2D+1 space-time wavepacket to broadband intermodal dispersive waves in multimode fibers.

Findings

Experimental confirmation of phase-matched radiations in multimode fibers

Theoretical predictions match experimental and numerical results

Identification of a localized 2D+1 space-time wavepacket during nonlinear propagation

Abstract

We provide a complete analysis, from theory to experiment, of the spontaneous emergence of a discretized conical wave of X-type (i.e., a localized 2D+1 space-time wavepacket) when an intense ultrashort pulse nonlinearly propagates in a multimode fiber. In particular, we reveal that this spatiotemporal phenomenon corresponds to broadband intermodal dispersive wave emission from an unsteady localized wave structure formed during nonlinear propagation. Theoretical phase-matching predictions are experimentally and numerically confirmed in a commercially-available step-index multimode fiber. Our results provide a general understanding of phase-matched radiations emitted by nonlinear waves in multidimensional dispersive optical system.