Classical Rayleigh-Jeans Condensation of Light Waves: Observation and Thermodynamic Characterization

K. Baudin, A. Fusaro, K. Krupa, J. Garnier, S. Rica, G. Millot, and A. Picozzi
Phys. Rev. Lett. 125, 244101 – Published 8 December 2020
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Abstract

Theoretical studies on wave turbulence predict that a purely classical system of random waves can exhibit a process of condensation, which originates in the singularity of the Rayleigh-Jeans equilibrium distribution. We report the experimental observation of the transition to condensation of classical optical waves propagating in a multimode fiber, i.e., in a conservative Hamiltonian system without thermal heat bath. In contrast to conventional self-organization processes featured by the nonequilibrium formation of nonlinear coherent structures (solitons, vortices,…), here the self-organization originates in the equilibrium Rayleigh-Jeans statistics of classical waves. The experimental results show that the chemical potential reaches the lowest energy level at the transition to condensation, which leads to the macroscopic population of the fundamental mode of the optical fiber. The near-field and far-field measurements of the condensate fraction across the transition to condensation are in quantitative agreement with the Rayleigh-Jeans theory. The thermodynamics of classical wave condensation reveals that the heat capacity takes a constant value in the condensed state and tends to vanish above the transition in the normal state. Our experiments provide the first demonstration of a coherent phenomenon of self-organization that is exclusively driven by optical thermalization toward the Rayleigh-Jeans equilibrium.

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  • Received 4 April 2020
  • Revised 25 September 2020
  • Accepted 16 November 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.244101

© 2020 American Physical Society

Physics Subject Headings (PhySH)

Nonlinear Dynamics

Authors & Affiliations

K. Baudin1, A. Fusaro1,2, K. Krupa1,3, J. Garnier4, S. Rica5, G. Millot1,6, and A. Picozzi1

  • 1Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS, Université Bourgogne Franche-Comté, 21078 Dijon, France
  • 2CEA, DAM, DIF, F-91297 Arpajon Cedex, France
  • 3Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland
  • 4CMAP, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
  • 5Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Avda. Diagonal las Torres 2640, Peñalolén, 7910000, Santiago, Chile
  • 6Institut Universitaire de France (IUF), 1 rue Descartes, 75005 Paris, France

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Issue

Vol. 125, Iss. 24 — 11 December 2020

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