Dramatic acceleration of wave condensation mediated by disorder in multimode fibers

Abstract

Classical nonlinear waves exhibit a phenomenon of condensation that results from the natural irreversible process of thermalization, in analogy with the quantum Bose-Einstein condensation. Wave condensation originates in the divergence of the thermodynamic equilibrium Rayleigh-Jeans distribution, which is responsible for the macroscopic population of the fundamental mode of the system. However, achieving complete thermalization and condensation of incoherent waves through nonlinear optical propagation is known to require prohibitive large interaction lengths. Here, we derive a discrete kinetic equation describing the nonequilibrium evolution of the random wave in the presence of a structural disorder of the medium. Our theory reveals that a weak disorder accelerates the rate of thermalization and condensation by several order of magnitudes. Such a counterintuitive dramatic acceleration of condensation can provide a natural explanation for the recently discovered phenomenon of optical beam self-cleaning. Our experiments in multimode optical fibers report the observation of the transition from an incoherent thermal distribution to wave condensation, with a condensate fraction of up to 60% in the fundamental mode of the waveguide trapping potential.

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References in corpus (9)

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• Nonlinear propagation in multi-mode fibers in the strong coupling regime
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Cited by in corpus (6)

• Thermodynamic theory of highly multimoded nonlinear optical systems
• Wave condensation with weak disorder versus beam self-cleaning in multimode fibers
• Entropic thermodynamics of nonlinear photonic chain networks
• Modal dynamics in multimode optical fibers: An attractor of high-order modes
• Incoherent localized structures and hidden coherent solitons from the gravitational instability of the Schrödinger-Poisson equation
• Spatial beam self-cleaning in bi-tapered multimode fibers