Semiconductor excitations can hybridize with cavity photons to form exciton-polaritons (EPs) with remarkable properties, including light-like energy flow combined with matter-like interactions. To fully harness these properties, EPs must retain ballistic, coherent transport despite matter-mediated interactions with lattice phonons. Here we develop a nonlinear momentum-resolved optical approach that directly images EPs in real space on femtosecond scales in a range of polaritonic architectures. We focus our analysis on EP propagation in layered halide perovskite microcavities. We reveal that EP–phonon interactions lead to a large renormalization of EP velocities at high excitonic fractions at room temperature. Despite these strong EP–phonon interactions, ballistic transport is maintained for up to half-exciton EPs, in agreement with quantum simulations of dynamic disorder shielding through light-matter hybridization. Above 50% excitonic character, rapid decoherence leads to diffusive transport. Our work provides a general framework to precisely balance EP coherence, velocity, and nonlinear interactions.

半导体激发可以与腔光子杂交形成具有卓越特性的激子极化子（EP），包括类光能量流与类物质相互作用相结合。为了充分利用这些特性，尽管存在物质介导的与晶格声子的相互作用，EP 仍必须保持弹道、相干的传输。在这里，我们开发了一种非线性动量分辨光学方法，可以在一系列极化子结构中以飞秒尺度直接对真实空间中的 EP 进行成像。我们重点分析层状卤化物钙钛矿微腔中的 EP 传播。我们揭示了 EP-声子相互作用导致室温下高激子分数下 EP 速度的大幅重正化。尽管有这些强烈的 EP-声子相互作用，弹道输运仍可维持高达半激子 EP，与通过光-物质杂交进行动态无序屏蔽的量子模拟一致。激子特性超过 50% 时，快速退相干会导致扩散传输。我们的工作提供了一个精确平衡 EP 相干性、速度和非线性相互作用的通用框架。