Conditions for walk-off soliton generation in a multimode fiber

Mario Zitelli,Fabio Mangini,Stefan Wabnitz,Oleg Sidelnikov,Mario Ferraro

doi:10.1038/s42005-021-00687-0

Mario Zitelli, Fabio Mangini + Show 3 more

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https://doi.org/10.1038/s42005-021-00687-0

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Abstract

It has been recently demonstrated that multimode solitons are unstable objects which evolve, in the range of hundreds of nonlinearity lengths, into stable single-mode solitons carried by the fundamental mode. We show experimentally and by numerical simulations that femtosecond multimode solitons composed by non-degenerate modes have unique properties: when propagating in graded-index fibers, their pulsewidth and energy do not depend on the input pulsewidth, but only on input coupling conditions and linear dispersive properties of the fiber, hence on their wavelength. Because of these properties, spatiotemporal solitons composed by non-degenerate modes with pulsewidths longer than a few hundreds of femtoseconds cannot be generated in graded-index fibers.

Highlights

It has been recently demonstrated that multimode solitons are unstable objects which evolve, in the range of hundreds of nonlinearity lengths, into stable single-mode solitons carried by the fundamental mode
In a recent study[11], we observed that the beam content of femtosecond MM solitons propagating over relatively long spans of GRIN fiber is irreversibly attracted toward the fundamental mode of the multimode fibers (MMFs)
What we observed did not appear to obey the predictions of the variational theory for spatiotemporal solitons[13,14,15,16,17,18]: Figs. 1–3 provide the experimental evidence when using 120 m of GRIN fiber

Summary

Introduction

It has been recently demonstrated that multimode solitons are unstable objects which evolve, in the range of hundreds of nonlinearity lengths, into stable single-mode solitons carried by the fundamental mode. In a recent study[11], we observed that the beam content of femtosecond MM solitons propagating over relatively long spans of GRIN fiber is irreversibly attracted toward the fundamental mode of the MMF This is due to the combined action of intermodal four-wave mixing (IM-FWM) and stimulated Raman scattering (SRS). It is necessary to impose the additional condition that the walk-off distance is of the same order of the nonlinear and chromatic dispersion lengths The presence of this extra condition leads to a new class, to the best of our knowledge, of “walk-off” MM solitons composed of nondegenerate modes: they have a pulsewidth and energy, which are independent of the input pulse duration, and only depend on the fiber dispersive parameters, the soliton wavelength

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