Thesis Defense In Chemistry, Presented by Ding Xu
Spatiotemporal imaging of exciton-polariton transport and nonlinear optics in van der Waals semiconductors under strong light-matter coupling
Presented By: Ding Xu
Abstract:
Strong light–matter coupling in van der Waals (vdW) semiconductors offers a powerful platform for controlling coherent light transport, nonlinear optical processes, and spin–photon interactions at room temperature. Exciton-polaritons, hybrid quasiparticles of photons and excitons, open new avenues for translating the exotic quantum phenomena in vdW materials into practical quantum devices, enabling long-range coherence with strong interactions. Using ultrafast stroboSCAT, we directly visualize polariton transport in hybrid halide perovskite microcavities and reveal velocity-renormalized coherent propagation due to phonon interactions. In rhombohedral-stacked MoS₂ cavities, we successfully image waveguided polariton transport beyond the numerical aperture limits and investigate efficient second-harmonic generation under phase matching. We further demonstrate a robust optical spin Hall effect in NbOI₂ cavities arising from strong spin–orbit coupling, and observe pronounced spin-split photon currents and beam steering under edge-scattered excitation. We anticipate that our spatiotemporal imaging method will provide a powerful framework for understanding the intricate transport of polaritons and for guiding the design of polaritonic quantum circuits, microchip-scale quantum light sources, and other optoelectronic devices based on strong light-matter coupling semiconductors.