Extreme wave excitation from localized phase-shift perturbations

TL;DR

This paper demonstrates that localized phase-shift perturbations alone can trigger rogue waves in nonlinear dispersive media, confirmed through wave tank experiments consistent with NLSE predictions.

Contribution

It introduces a novel focusing mechanism where phase-shifts, without amplitude modulation, generate extreme waves, expanding understanding of rogue wave formation.

Findings

Phase-shift localization can trigger rogue waves.

Wave tank experiments align with NLSE hydrodynamics.

Breather-type extreme waves can originate from regular wave trains.

Abstract

The modulation instability is a focusing mechanism responsible for the formation of strong wave localizations not only on the water surface, but also in a variety of nonlinear dispersive media. Such dynamics is initiated from the injection of side-bands, which translate into an amplitude modulation of the wave field. The nonlinear stage of unstable wave evolution can be described by exact solutions of the nonlinear Schr\"odinger equation (NLSE). In that case, the amplitude modulation of such coherent extreme wave structures is connected to a particular phase-shift seed in the carrier wave. In this letter, we show that phase-shifts localization applied to the background, excluding any amplitude modulation excitation, can indeed trigger extreme events. Such rogue waves can be for instance generated by considering the parametrization of fundamental breathers and thus, by seeding only the local phase-shift information to the regular carrier wave. Our wave tank experiments show an excellent agreement with the expected NLSE hydrodynamics and confirm that even though delayed in their evolution, breather-type extreme waves can be generated from a purely regular wave train. Such novel focusing mechanism awaits experimental confirmation in other nonlinear media, such optics, plasma, and Bose-Einstein condensates.