Regulation of strong coupling between multiple BICs and excitons in bulk WS2 metasurfaces

Bulk transition metal dichalcogenides have become staples in nanophotonics, condensed matter physics, and quantum optics due to their elevated refractive index and the reliable exciton response they maintain at room temperature. In our research, we harness block WS₂ to engineer an ultra-thin nanodisk metasurface capable of supporting both magnetic dipole Q-BIC (quasi-bound in the continuum) resonance and magnetic ring dipole Q-BIC resonance. Remarkably, these Q-BIC resonances are capable of self-hybridizing with excitons, facilitating intense light-matter interactions within the structure, independent of an external cavity. The self-hybridized exciton polaritons, a result of the strong coupling between Q-BIC and excitons, display characteristic anti-crossing behavior, with Rabi splittings reaching up to 161 meV and 165 meV, respectively. Building upon these findings, we utilize a Hamiltonian model that accounts for residual excitons, thereby substantiating the strong coupling phenomenon. Our discoveries hold significant promise for the manipulation of excitonic polaritons at room temperature, potentially leading to the development of large-scale, cost-effective integrated polaron devices that operate under room temperature.