Fig. 3: Room-temperature strong coupling in SPE-BIC systems.

a Experimental angle-resolved PL spectra (with excitation power \({P}_{{{{{{\rm{exc}}}}}}}\)~1.3²9 kW/cm²) (left) and the simulation (right) in a strong coupling regime, evidenced by the clear spectral splitting and vanishing emission at normal incidence on both polariton branches. b Antibunching dip g²(0) = 0.28 confirming the single-photon emission nature at the measured strong coupling spot. The experimental data (blue line) is fitted with a three-level model (red line). c PL spectra extracted at \(\theta=\) −3.06° (black squares) and the double-Lorentzian fitting (purple curve). The FWHM of the lower polariton branch (LBP) \({\gamma }_{{LBP}}=8.45\) meV and of the upper polariton branch (UBP) \({\gamma }_{{UBP}}=3.92\) meV are extracted from the fitting. d Energy (\(E\)) and e FWHM \(\gamma\) of the UBP (blue up-triangles) and the LBP (red circles) at different angles and the theoretical fitting using coupled oscillator model (solid black lines). The energies and FWHM of the uncoupled SPE and BIC modes are shown by dashed black lines.