Photon number-resolved measurement of an exciton-polariton condensate

TL;DR

This study measures the photon-number distribution of an exciton-polariton condensate, revealing the transition from thermal to coherent states and providing insights into coherence formation and phase transition mechanisms.

Contribution

It introduces photon-number resolved measurements of polariton condensates, enabling direct analysis of state evolution and higher-order correlations during the phase transition.

Findings

Photon-number distribution shifts from geometric to quasi-Poissonian with increased excitation power.

Higher-order photon correlations provide insights into coherence and phase transition.

Thermal and coherent fractions are directly extracted from measured distributions.

Abstract

We measure the full photon-number distribution emitted from a Bose condensate of microcavity exciton-polaritons confined in a micropillar cavity. The statistics are acquired by means of a photonnumber resolving transition edge sensor. We directly observe that the photon-number distribution evolves with the non-resonant optical excitation power from geometric to quasi-Poissonian statistics, which is canonical for a transition from a thermal to a coherent state. Moreover, the photon-number distribution allows evaluating the higher-order photon correlations, shedding further light on the coherence formation and phase transition of the polariton condensate. The experimental data is analyzed in terms of thermal coherent states which allows one to directly extract the thermal and coherent fraction from the measured distributions. These results pave the way for a full understanding of the contribution of interactions in light-matter condensates in the coherence buildup at threshold.