Long-Range Exciton Transport in Microcavity Exciton-Polariton Systems*

It has previously been assumed that the transport distance of excitons in microcavity exciton-polariton systems is limited by the bare exciton diffusion length (≤ 1 μm). In the case of non-resonant excitation, this implies that excitons created by the pump laser would be mostly confined to the pump location. While this is clearly generally true given the close similarities between the spatial pump and lower polariton potential profiles, we show that there is an important minority population of slightly polaritonic excitons that can move distances similar to those of the much more photonic polaritons (≈ 30 μm). This population, which resides in the bottleneck region of the lower polariton branch, is often not detected in a typical photoluminescence experiment due to limited numerical aperture. While small in number compared to the total population of excitons, they can substantially outnumber the polaritons below the bottleneck. This has significant implications for creating potential landscapes using a non-resonant pump, and for measurements of the interaction strength between polaritons.