Thermalization kinetics of light: From laser dynamics to equilibrium condensation of photons

TL;DR

This study investigates the real-time thermalization and condensation of photons in a dye microcavity, revealing the transition from laser behavior to Bose-Einstein condensation based on photon thermalization dynamics.

Contribution

It provides the first in-situ, time-resolved observation of photon thermalization and the crossover from lasing to Bose-Einstein condensation in a dye microcavity.

Findings

Photon thermalization leads to Bose-Einstein distribution and condensation.

Fast thermalization results in photon BEC, slow thermalization results in lasing.

Real-time monitoring captures the transition dynamics.

Abstract

We report a time-resolved study of the thermalization dynamics and the lasing to photon Bose-Einstein condensation crossover by in-\textit{situ} monitoring the photon kinetics in a dye microcavity. When the equilibration of the light to the dye temperature by absorption and re-emission is faster than photon loss in the cavity, the optical spectrum becomes Bose-Einstein distributed and photons accumulate at low-energy states, forming a Bose-Einstein condensate. The thermalization of the photon gas and its evolution from nonequilibrium initial distributions to condensation is monitored in real-time. In contrast, if photons leave the cavity before they thermalize, the system operates as a laser.