  Photonic topological insulators are a promising photonic platform due to the
possibility of unidirectional edge states with insensitivity to bending,
fabrication imperfections or environmental fluctuation. Here we demonstrate
highly efficient unidirectional photonic edge mode propagation facilitated by
an optical analogue of the quantum valley Hall effect. With an all-dielectric
kagome lattice design, we demonstrate broadband suppressed reflection in the
presence of sharp corners and further show negligible vertical losses in a
semiconductor-based device at telecommunication wavelengths.
