English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Open

Presents the pdf analysis as premium feature

PDF Analysis

Insights

Presents the summarisation as premium feature

Summarisation

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Classical nonlinear waves exhibit, as a general rule, an irreversible processof thermalization toward the Rayleigh-Jeans equilibrium distribution. On theother hand, several recent experiments revealed a remarkable effect of spatialorganization of an optical beam that propagates through a graded-indexmultimode optical fiber (MMF), a phenomenon termed beam self-cleaning. Our aimhere is to evidence the qualitative impact of disorder (weak random modecoupling) on the process of Rayleigh-Jeans thermalization by considering twodifferent experimental configurations. In a first experiment, we launch specklebeams in a relatively long MMF. Our results report a clear and definiteexperimental demonstration of Rayleigh-Jeans thermalization through lightpropagation in MMFs, over a broad range of kinetic energy (i.e., degree ofspatial coherence) of the injected speckle beam. In particular, the property ofenergy equipartition among the modes is clearly observed in the condensedregime. The experimental results also evidence the double turbulence cascadeprocess: while the power flows toward the fundamental mode (inverse cascade),the energy flows toward the higher-order modes (direct cascade). In a 2ndexperiment, a coherent laser beam is launched into a relatively short MMFlength. It reveals an effect of beam cleaning driven by an incipient process ofRayleigh-Jeans thermalization. As discussed through numerical simulations, thefast process of Rayleigh-Jeans thermalization observed in the 1st experimentcan be attributed due to a random phase dynamics among the modes, which isfavoured by the injection of a speckle beam and the increased impact ofdisorder in the long fiber system.

Rayleigh-Jeans thermalization vs beam cleaning in multimode optical fibers