Spatial cage solitons -- taming light bullets

TL;DR

This paper introduces a formalism for understanding spatial cage solitons in multimode fibers, revealing stable light bullets and expanding the potential for high-power pulse compression in fiber optics.

Contribution

It extends mode-locking theory to spatial modes, predicting stable spatio-temporal solitons and providing insights into their formation in multimode fibers.

Findings

Unveils coexistence of two soliton branches for anomalous dispersion.

Predicts stable spatio-temporal light bullets in multimode fibers.

Provides a framework for understanding high-power pulse compression.

Abstract

Multimode nonlinear optics offers to overcome a long-standing limitation of fiber optics, tightly phase locking several spatial modes and enabling the coherent transport of a wavepacket through a multimode fiber. A similar problem is encountered in the temporal compression of multi-mJ pulses to few-cycle duration in hollow gas-filled fibers. Scaling the fiber length to up to six meters, hollow fibers have recently reached 1 TW of peak power. Despite the remarkable utility of the hollow fiber compressor and its widespread application, however, no analytical model exists to enable insight into the scaling behavior of maximum compressibility and peak power. Here we extend a recently introduced formalism for describing mode-locking to the spatially analogue scenario of locking spatial fiber modes together. Our formalism unveils the coexistence of two soliton branches for anomalous modal dispersion and indicates the formation of stable spatio-temporal light bullets that would be unstable in free space, similar to the temporal cage solitons in mode-locking theory. Our model enables deeper understanding of the physical processes behind the formation of such light bullets and predict the existence of multimode solitons in a much wider range of fiber types than previously considered possible.