Figure 6.

Propagation velocities for plexcitons along Y-axis (a) and X-axis (c) for three different plasmonic crystals calculated from the angular dispersions compared to the values extracted from the coupled-oscillator model. The photon fractions correlate with the increase of velocity reaching the speed of light in a medium c/n with n = 1.5. Corresponding propagation lengths for plexcitons along Y-axis (b) and X-axis (d) calculated from their velocities and lifetimes compared to the spatial coherence lengths extracted from the reciprocal-space linewidth. Calculated polar plots of normalized group velocities (f) and effective masses (h) of plexcitons along phase velocity directions indicated in part e. (g) Group velocity polar plots for plexcitons of different wavelengths.