Broadband Localization of Light at the Termination of a Topological Photonic Waveguide

Photonic systems with non-trivial topology of their bulk bands offer exciting routes to controlling light and its interaction with matter at the nanoscale. Specifically, edge states in topological waveguides with a conserved valley degree of freedom are characterized by suppressed backscattering at lattice discontinuities such as sharp corners or defects. Therefore, the intentional termination of a topological waveguide leads to interesting scattering phenomena involving a delay in the valley-flip of the edge state. Theory has predicted a sharp localization of light at such a termination, with potential high impact to enhancing light-matter interactions and non-linearities [1], [2].