Z₂ Topological Photonics for Robust Transport in the Visible Spectrum

Topological photonics aims to realize optical analogs of topological states of matter using photonic circuits. Since topological edge states are protected from defect scattering, quantum superpositions generated by strong light-matter interactions can be transferred without loss by photons in a topological photonic circuit. However, there are so far very few studies of light-matter interactions in topological photonics due to the mismatch between topological photonic circuit designs and promising materials for integrating with them. In this work, we propose and demonstrate a novel topological photonic structure together with an overetch procedure that can open a complete optical band gap in the visible spectral region using low index contrast materials. Devices following this design have been fabricated and evaluated via transmission and imaging experiments. These results demonstrate the existence of topological edge states with this design and the robustness of edge states against scattering. This topological photonics design is suitable for integrating with visible-wavelength materials with minimal fabrication challenges.