Room-temperature strong coupling at the nanoscale achieved by inverse design

Abstract: Room-temperature strong coupling between plasmonic nanocavities and monolayer semiconductors is a prominent path towards efficient, integrated light-matter interactions. However, designing such systems is challenging due to the nontrivial dependence of the strong coupling on various properties of the cavity and emitter, as well as the subwavelength scale of the interaction. In this work, we develop a methodology for obtaining hybrid nanostructures consisting of plasmonic metasurfaces coupled to atomically thin WS2 layers, exhibiting extreme values of Rabi splitting, by inverse design of the near-field plasmonic response. Contrary to common measures such as the quality factor or the mode volume, our method relies on an overlap-integral-based metric. We experimentally measure large values of Rabi splitting for our nanoantenna designs, while providing theoretically optimal configurations for several additional types of nanostructures. Our results open a path to maximizing light-matter interactions in integrated platforms, for classical and quantum-optical applications.