An apparatus for coupling two-dimensional materials to cavity photons.

We develop a cryogenic, multimode confocal cavity-QED platform for CW hybrid light–matter states. Near confocality yields many near-degenerate transverse modes whose "supermodes" concentrate intensity at a 2D sample, boosting cooperativity while keeping wide optical access. The cavity is integrated into a cryostat; the sample is heat-sunk through a vibration-filtering link, and the lock error/feedback serves as an in-situ vibration sensor. Initial experiments probe cavity–exciton coupling in monolayer MoSe2 and WSe2 via longitudinal spectroscopy, tuning the cavity across the exciton and recording the cavity-coupled spectrum to seek vacuum Rabi splitting.