Fig. 4: Vibrational strong coupling of SiC qBICs with PEG.

a, Experimental and simulated transmission spectra of bare SiC metasurfaces with scaling factors ranging from 0.4 to 1.5. b, Schematic of vibrational strong coupling. The BIC resonance is spectrally overlapped with the absorption band of PEG, resulting in a splitting of the BIC mode into upper and lower polaritonic states. c, Experimentally resolved and simulation-resolved anticrossing of SiC metasurfaces covered with 30-nm-thick PEG. The dotted lines denote the polariton dispersion calculated using the extracted parameters from TCMT fitting and a Rabi splitting of 11.5 cm⁻¹.