Higher order coherence of exciton-polariton condensates

TL;DR

This study measures higher order coherence functions of exciton-polariton condensates, revealing non-ideal bunching behavior that differs from thermal or laser states, and aligns with a model involving polariton interactions.

Contribution

It provides the first detailed experimental measurement of third order coherence in exciton-polariton condensates and compares it with a theoretical model including interactions.

Findings

Observed deviation from unity in $g^{(2)}(0)$ and $g^{(3)}(0)$ indicating bunching.

Found $g^{(3)}(0) > g^{(2)}(0) > 1$, showing non-coherent, non-thermal behavior.

Experimental results agree with a model including polariton-polariton and polariton-phonon interactions.

Abstract

The second and third order coherence functions $g^{(n)}(0) (n=2 {\rm and} 3)$ of an exciton-polariton condensate is measured and compared to the theory. Contrary to an ideal photon laser, deviation from unity in the second and third order coherence functions is observed, thus showing a bunching effect, but not the characteristics of a standard thermal state with $g^{(n)}(0)=n!$. The increase of bunching with the order of the coherence function, $g^{(3)}(0) > g^{(2)}(0)>1$, indicates that the polariton condensate is different from coherent state, number state and thermal state. The experimental results are in agreement with the theoretical model where polariton-polariton and polariton-phonon interactions are responsible for the loss of temporal coherence.