Fig. 2

Strong coupling between TE-polarized WSe₂ exciton and PC modes measured by angle-resolved reflectance and PL at 10 K. The top/bottom row shows the along-bar/cross-bar directions, respectively. The left/right panels of a–c show the measured/simulated results, respectively. a Angle-resolved reflectance spectra of the bare PC, showing a sharp, dispersive PC mode. b Angle-resolved reflectance spectra of the WSe₂-PC integrated device, showing split, anti-crossing upper and lower polariton modes. c Angle-resolved PL data (left) compared with the simulated absorption spectra of the WSe₂-PC integrated device, showing the same anti-crossing polariton modes as in b. d The polariton energies E_LP,UP vs. wavevector k _x , k _y obtained from the spectra in c. The lines are fits to the LP and UP dispersion with the coupled harmonic oscillator model, giving a vacuum Rabi splitting of 18.4 and 16.1 meV for the along-bar (top) and cross-bar (bottom) directions, respectively. The corresponding Hopfield coefficients |C²| and |X²|, representing the photon and exciton fractions in the LP modes, respectively, are shown in the top sub-plots