Breakdown of Temporal Coherence in Photon Condensates

TL;DR

This paper investigates why photon condensates exhibit decreasing coherence times above the critical pump power, contrasting with ideal Bose gases, and identifies intermode correlations as the key factor.

Contribution

It reveals that intermode correlations cause the decline in coherence time in photon condensates beyond the threshold, challenging previous expectations based on ideal Bose gases.

Findings

Coherence time decreases rapidly above threshold in photon condensates.

Intermode correlations are identified as the main cause of coherence breakdown.

Contrasts with ideal Bose gas behavior where coherence diverges at the threshold.

Abstract

The temporal coherence of an ideal Bose gas increases as the system approaches the Bose-Einstein condensation threshold from below, with coherence time diverging at the critical point. However, counter-examples have been observed for condensates of photons formed in an externally pumped, dye-filled microcavity, wherein the coherence time decreases rapidly for increasing particle number above threshold. This paper establishes intermode correlations as the central explanation for the experimentally observed dramatic decrease in the coherence time beyond critical pump power.