Laser operation and Bose-Einstein condensation: analogies and differences

TL;DR

This paper reviews the analogy between laser operation and Bose-Einstein condensation, highlighting differences due to non-equilibrium conditions, and proposes a criterion to distinguish equilibrium from non-equilibrium condensates using fluctuation-dissipation relations.

Contribution

It introduces a quantitative criterion to experimentally differentiate equilibrium and non-equilibrium Bose-Einstein condensates based on fluctuation-dissipation relations.

Findings

Experimental features of non-equilibrium photon and polariton condensates are illustrated.

A new criterion for assessing equilibrium vs. non-equilibrium condensates is proposed.

Model analyses demonstrate the criterion's effectiveness in different scenarios.

Abstract

After reviewing the interpretation of laser operation as a non-equilibrium Bose-Einstein condensation phase transition, we illustrate the novel features arising from the non-equilibrium nature of photon and polariton Bose-Einstein condensates recently observed in experiments. We then proposea quantitative criterion to experimentally assess the equilibrium vs. non-equilibrium nature of a specific condensation process, based on fluctuation-dissipation relations. The power of this criterion is illustrated on two models which shows very different behaviours.