Room-Temperature Exciton Polaritons in Monolayer WS₂ Enabled by Plasmonic Bound States in the Continuum

Exciton polaritons formed by the strong coupling between excitons and photons have been extensively studied in transition metal disulfides (TMDs) for their potential to inherit ultralong radiation lifetime and remarkable nonlinearity. Many studies have achieved strong coupling at room temperature. However, the systems in these studies generally lack orderly characteristics and precise controllability, and their tunability also remains rather limited. Here, we demonstrate a plasmonic grating with a bound state in the continuum (BIC) as a highly tunable platform for generating exciton polaritons in monolayer WS₂ at room temperature. We characterized the polariton modes and determined an energy splitting of 93 meV. This validates strong coupling in our system. Our research offers a new approach for exploring exciton polaritons in 2D semiconductors, opening doors for room-temperature optoelectronic and quantum computing applications.