We report an experimental study of the spontaneous spatial and temporal coherence of polariton condensates generated in the optical parametric oscillator configuration, below and at the parametric threshold, and as a function of condensate area. Above the threshold we obtain very long coherence times (up to 3 ns) and a spatial coherence extending over the entire condensate (40 \mu m). The very long coherence time and its dependence on condensate area and pump power reflect the suppression of polariton-polariton interactions by an effect equivalent to motional narrowing.
@article{arxiv.1111.4894,
title = {Build up of off-diagonal long-range order in microcavity exciton-polaritons across the parametric threshold},
author = {R. Spano and J. Cuadra and C. Lingg and D. Sanvitto and M. D. Martin and P. R. Eastham and M. van der Poel and J. M. Hvam and L. Vina},
journal= {arXiv preprint arXiv:1111.4894},
year = {2011}
}