Fig. 4: Dispersive propagation losses in a slow-light glide-symmetric VH waveguide.
From: Observation of strong backscattering in valley-Hall photonic topological interface modes
a, Wavelength dependence of the measured propagation loss (solid black line) obtained from the fit coefficients (Fig. 3g), with the shaded area indicating the standard error. The propagation loss is fitted with the model in equation (3) (red line) and the trivial–topological transition shaded according to the found wavelength offset. The solid segments of the fit line indicate the intervals that were fitted. The calculated intrinsic loss above the light line is included for reference (solid green line). The location of the K valley in the topological mode is indicated by a vertical blue line. b, Dependence of the loss on the group index, ng, where the wavelength–group-index conversion is derived from the fit in a.
