Dynamics and correlations of a Bose-Einstein condensate of photons

TL;DR

This paper reviews recent experimental progress in understanding the dynamics and correlations of a photon Bose-Einstein condensate confined in a microcavity, highlighting the first realization of grand-canonical ensemble conditions.

Contribution

It reports the first experimental observation of Bose-Einstein condensation of photons under grand-canonical conditions facilitated by dye molecules.

Findings

Photon condensate exhibits characteristic number and phase correlations.

Repeated absorption-emission processes enable thermal coupling to a heat bath.

First experimental access to grand-canonical statistical ensemble in photon BEC.

Abstract

The Tutorial reports recent experimental advances in studies of the dynamics as well as the number and phase correlations of a Bose-Einstein condensed photon gas confined in a high-finesse dye-filled microcavity. Repeated absorption-emission-processes of photons on dye molecules here establish a thermal coupling of the photonic quantum gas to both a heat bath and a particle reservoir comprised of dye molecules. In this way, for the first time Bose-Einstein condensation under grand-canonical statistical ensemble conditions becomes experimentally accessible.