Energy and wave-action flows underlying Rayleigh-Jeans thermalization of optical waves propagating in a multimode fiber

Year: 2021

Authors: Baudin K.; Fusaro A.; Garnier J.; Berti N.; Krupa K.; Carusotto I; Rica S.; Millot G.; Picozzi A.

Autors Affiliation: Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS, University Bourgogne Franche- Comte, Dijon, France; CEA, DAM, DIF, Arpajon, F-91297, France; CMAP, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau Cedex, 91128, France; Institute of Physical Chemistry Polish Academy of Sciences, Warsaw, 01-224, Poland; INO-CNR BEC Center and Dipartimento di Fisica, Universit di Trento, Povo (TN), I-38123, Italy; Universidad Adolfo Ibbntilde;ez – Pentilde;alolyn, Santiago, 7910000, Chile; Institut Universitaire de France (IUF), 1 rue Descartes, Paris, 75005, France

Abstract: The wave turbulence theory predicts that a conservative system of nonlinear waves can exhibit a process of condensation, which originates in the singularity of the Rayleigh-Jeans equilibrium distribution of classical waves. Considering light propagation in a multimode fiber, we show that light condensation is driven by an energy flow toward the higher-order modes, and a bi-directional redistribution of the wave-action (or power) to the fundamental mode and to higher-order modes. The analysis of the near-field intensity distribution provides experimental evidence of this mechanism. The kinetic equation also shows that the wave-action and energy flows can be inverted through a thermalization toward a negative temperature equilibrium state, in which the high-order modes are more populated than low-order modes. In addition, a Bogoliubov stability analysis reveals that the condensate state is stable. Copyright (C) 2021 EPLA

Journal/Review: EPL

Volume: 134 (1)      Pages from: 14001-1  to: 14001-7

DOI: 10.1209/0295-5075/134/14001