Extended Data Fig. 1: Comparison of staggered and flat-phased broad excitations.

(a-d): Staggered excitations of the primary waveguides of edge unit cells successfully populate the topological Chern mode near the edge of the Brillouin zone. (e-h) Absent the appropriate phase modulation, the injected wave packets instead represent a superposition of the bulk bands near the center of the Brillouin zone. As a result, the light diffracts freely across the entire lattice instead of being captured in the helical Chern channel.