Strong coupling of excitons in a two-dimensional atomic crystal with quasi-bound state in the continuum supported by a single nanoparticle

Bound states in the continuum (BICs) supported by high-index dielectric nanoparticles have garnered significant attention due to their ability to achieve subwavelength confinement with high-quality factors, offering great potential for both fundamental studies of light–matter interactions and the development of compact photonic devices. However, the strong coupling of BICs with quantum emitters in single-particle systems has not been reported. In this paper, we propose a dielectric nanodisk integrated with a monolayer of transition metal dichalcogenides. A supercavity mode known as Friedrich–Wintgen BIC is launched in the nanodisk to enable strong coupling of BIC with WS2 excitons. We demonstrate that the reduction in coupling strength as the quasi-BIC quality factor increases is due to a decrease in the number of excitons participating in the coupling. Additionally, the coupling strength can be manipulated by adjusting the shape and aspect ratio of the nanoresonators, enabling a transition from strong to weak coupling regimes. Near-field analysis shows that the manipulation of the BIC–exciton interaction arises from the overlap of the BIC mode's near-field with the excitons. Our findings offer a promising strategy for manipulating light–matter interactions and enhance the potential applications of BIC resonances in photonics.