Abstract

Photonic topological insulators with robust boundary states can enable great applications for optical communication and quantum emission, such as unidirectional waveguide and single-mode laser. However, because of the diffraction limit of light, the physical insight of topological resonance remains unexplored in detail, like the dark line that exists with the crystalline symmetry-protected topological edge state.

Here, we experimentally observe the dark line of the Z₂ photonic topological insulator in the visible range by photoluminescence and specify its location by cathodoluminescence characterization, and elucidate its mechanism with the p-d orbital electromagnetic field distribution which calculated by numerical simulation. Our investigation provides a deeper understanding of Z₂ topological edge states and may have great significance to the design of future on-chip topological devices.