First and second order coherence of exciton-polariton condensates

The microcavity exciton-polariton system offers the possibility to study condensed matter physics with optical techniques. In particular, condensation of microcavity exciton-polaritons in momentum space, as well as spontaneous buildup of spatial and temporal coherence, were recently demonstrated. We investigate the first and second order coherence of exciton-polariton condensates both in coordinate and in momentum space. We measured the spatial coherence length of up to 20 $\mu m$, while $g^{(2)}(t=0)$ was measured to be close to 2 for appropriate near- and far-field filtering. This experiment provides insights into the phase and intensity fluctuations induced by polariton interactions.