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 $\rm Ta_2O_5$ periodic photonic structures and excitons in $\rm WSe_2$ monolayers. We demonstrate that giant radiative lifetime of BICs allow to engineer the exciton-polariton lifetime enhancing it three orders of magnitude compared to a bare exciton. We show that maximal lifetime of hybrid light-matter state can be achieved at any point of $\mathbf{k}$-space by shaping the geometry of the photonic structure. Our findings open new route for the realization of the moving exciton-polariton condensates with non-resonant pump and without the Bragg mirrors which is of paramount importance for polaritonic devices.