Diffraction of deep-water solitons

TL;DR

This study experimentally demonstrates that deep-water gravity-wave solitons can maintain their nonlinear characteristics while undergoing diffraction in the transverse dimension, revealing a coexistence of soliton stability and wave diffraction.

Contribution

The paper provides the first experimental evidence that deep-water solitons can preserve their nonlinear nature during diffraction, combining soliton dynamics with classical wave diffraction laws.

Findings

Solitons retain their nonlinear properties during diffraction.

Transverse wave profiles follow linear Fresnel diffraction laws.

Solitonic content remains stable along propagation.

Abstract

Solitons are localized nonlinear wave packets that propagate without spreading because nonlinearity balances dispersion. Their robustness is well understood in effectively one-dimensional systems, but introducing additional spatial dimensions is generally expected to destabilize them or destroy their coherent character. Here we experimentally investigate how deep-water gravity-wave solitons behave when a controlled transverse degree of freedom is introduced through diffraction. Using a large-scale water-wave facility, we generate solitonic wave packets whose transverse structure is imposed across a segmented wavemaker through either a sharp slit or a smooth Gaussian apodization. The resulting two-dimensional wave fields are measured with high spatial resolution. Diffraction reshapes the transverse profile of the wave packet while its longitudinal dynamics retain the characteristic features of a soliton. Nonlinear spectral analysis confirms that the solitonic content is preserved along the direction of propagation, whereas the transverse evolution follows the linear Fresnel laws of diffraction. These observations reveal an unexpected coexistence of nonlinear soliton dynamics and classical wave diffraction.