Spatio-temporal thermalization and adiabatic cooling of guided light waves

TL;DR

This paper introduces a theoretical framework for three-dimensional spatio-temporal thermalization of guided light waves in multi-mode waveguides, revealing mechanisms for adiabatic cooling and beam condensation.

Contribution

It combines wave turbulence theory with numerical simulations to demonstrate accelerated thermalization and cooling in guided light, advancing understanding of spatial and temporal beam cleaning.

Findings

Thermalization is accelerated by strong transverse confinement.

The process enables adiabatic cooling of the light beam.

It suggests a mechanism for spatial beam condensation.

Abstract

We propose and theoretically characterize three-dimensional spatio-temporal thermalization of a continuous-wave classical light beam propagating along a multi-mode optical waveguide. By combining a non-equilibrium kinetic approach based on the wave turbulence theory and numerical simulations of the field equations, we anticipate that thermalizing scattering events are dramatically accelerated by the combination of strong transverse confinement with the continuous nature of the temporal degrees of freedom. In connection with the blackbody catastrophe, the thermalization of the classical field in the continuous temporal direction provides an intrinsic mechanism for adiabatic cooling and, then, spatial beam condensation. Our results open new avenues in the direction of a simultaneous spatial and temporal beam cleaning.