Strong coupling between excitons in transition metal dichalcogenides and optical bound states in the continuum

Being motivated by recent achievements in the rapidly developing fields of optical bound states in the continuum (BICs) and excitons in monolayers of transition metal dichalcogenides, we analyze strong coupling between BICs in Ta₂O₅ periodic photonic structures and excitons in WSe₂ monolayers. We demonstrate that the giant radiative lifetime of a BIC allows us to engineer the exciton-polariton lifetime, enhancing it by two orders of magnitude compared to a bare exciton. We show that the maximal lifetime of a hybrid light-matter state can be achieved at any point of k space by shaping the geometry of the photonic structure. Our findings open a different route for the realization of moving exciton-polariton condensates with a nonresonant pump and without Bragg mirrors, which is of paramount importance for polaritonic devices.