We show the first experimental demonstration of room-temperature
exciton–polariton (EP) condensation from a bound state in the
continuum (BIC). This demonstration is achieved by strongly coupling
stable excitons in an organic perylene dye with the extremely long-lived
BIC in a dielectric metasurface of silicon nanoparticles. The long
lifetime of the BIC, mainly due to the suppression of radiation leakage,
allows for EP thermalization to the ground state before decaying.
This property results in a condensation threshold of less than 5 μJ
cm–2, 1 order of magnitude lower than the lasing
threshold reported in similar systems in the weak coupling limit.