19. Photoswitchable Rabi Splitting in Hybrid Plasmon–Waveguide Modes

Rabi splitting that arises from strong plasmon-molecule coupling has attracted tremendous interests. However, it has remained elusive to integrate Rabi splitting into the hybrid plasmon-waveguide modes (HPWMs), which have advantages of both subwavelength light confinement of surface plasmons and long-range propagation of guided modes in dielectric waveguides. Herein, we explore a new type of HPWMs based on hybrid systems of Al nanodisk arrays covered by PMMA thin films that are doped with photochromic molecules and demonstrate the photoswitchable Rabi splitting with a maximum splitting energy of 572 meV in the HPWMs by controlling the photoisomerization of the molecules. Through our experimental measurements combined with finite-difference time-domain (FDTD) simulations, we reveal that the photoswitchable Rabi splitting arises from the switchable coupling between the HPWMs and molecular excitons. By harnessing the photoswitchable Rabi splitting, we develop all-optical light modulators and rewritable waveguides. The demonstration of Rabi splitting in the HPWMs will further advance scientific research and device applications of hybrid plasmon-molecule systems.