Figure 2. Observation of strong exciton–photon coupling in a MoSe₂ single-QW heterostructure.

(a) A clear anticrossing in PL is observed between the discrete cavity mode energies and the neutral exciton energy at 4.2 K. The longitudinal resonance is labelled TEM₀₀. (b) The upper and lower polariton branches are fitted for the longitudinal mode with a vacuum Rabi splitting of 20 meV. (c) PL spectra of the longitudinal mode at various exciton–photon detunings from Δ=−16 meV (bottom) to Δ=+12 meV (top). (d) The PL spectrum on resonance shows the UPB and LPB well resolved. (e) The linewidth of the LPB and UPB as a function of detuning (black and red symbols, respectively). On resonance, the linewidth for LPB and UPB is around 4.8 and 8.5 meV, respectively. At a negative detuning of Δ=−25 meV, the LPB is broadened due to weak coupling with the charged exciton state.