Classical Rayleigh-Jeans condensation of light waves: Observation and thermodynamic characterization
Résumé
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.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...