Modulational instabilities play a key role in a wide range of nonlinear optical phenomena, leading, e.g., to the formation of spatial and temporal solitons, rogue waves, and chaotic dynamics. Here, we experimentally demonstrate the existence of a modulational instability in condensates of cavity polaritons, quasi-particles arising from the strong coupling of cavity photons with quantum well excitons. For this purpose, we investigate the spatiotemporal coherence properties of polariton condensates in GaAs-based microcavities under continuous-wave pumping. The chaotic behavior of the instability results in a strongly reduced spatial and temporal coherence and a significantly inhomogeneous density. Additionally, we show how the instability can be tamed by introducing a periodic potential so that condensation occurs in negative mass states, leading to largely improved coherence and homogeneity. These results pave the way to the exploration of long-range order in dissipative quantum fluids of light within a controlled platform.

中文翻译：

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极化子凝聚的不稳定和稳定状态

调制不稳定性在广泛的非线性光学现象中起关键作用，例如，导致空间和时间孤子，无赖波和混沌动力学的形成。在这里，我们通过实验证明了腔极化子的凝聚态中存在调制不稳定性，这是由于腔光子与量子阱激子的强耦合而产生的准粒子。为此，我们研究了连续波泵浦下基于GaAs的微腔中极化子冷凝物的时空相干特性。不稳定性的混沌行为导致空间和时间的连贯性大大降低，密度显着不均匀。此外，我们展示了如何通过引入周期性电势来抑制不稳定性，以便在负质量状态下发生凝结，从而大大提高了连贯性和同质性。这些结果为在受控平台内的光的耗散量子流体中探索远距离有序铺平了道路。