Insulator-free topological photonic multi-lane highways

TL;DR - A topological waveguide architecture enables robust, multi-lane, unidirectional light transport without insulating layers. Its closely stacked design achieves 100% spatial efficiency, potentially enabling denser photonic routing.

• Uses four inequivalent photonic valley half-semimetals in a parallel, cyclic configuration.
• Eliminates the insulating separation typically used between topological waveguides.
• Supports robust one-way light propagation across multiple lanes.
• Closely stacked lanes retain 100% spatial efficiency.