Atomically imprinted graphene plasmonic cavities*

The ability to design spatial patterns of high carrier density in two-dimensional materials with nanoscale cavity and circuitry features underlies future progress in nonlinear nanophotonics and strong light-matter interactions. Here, we present a general strategy to atomically imprint low-loss graphene plasmonic structures using oxidation-activated charge transfer (OCT). We covered charge-neutral graphene with a monolayer of WSe₂, which is subsequently oxidized into a high work-function monolayer WO_x to activate charge transfer. Our nano-infrared imaging reveals low-loss plasmon polaritons at the WO_x/graphene interface. We insert WSe₂ spacers to precisely control the OCT-induced carrier density and to achieve near-intrinsic quality factor of plasmons. Finally, we highlight canonical examples of plasmonic cavities imprinted via programmable OCT, exhibiting laterally abrupt doping profiles with single-digit nanoscale precision. In particular, we demonstrated technologically appealing but elusive plasmonic whispering-gallery resonators based on graphene using OCT-induced free-standing photonic platforms. Our results open avenues for novel quantum photonic architectures incorporating two-dimensional materials.