Insulator-free topological photonic multi-lane highways

Area of Science:

• Photonics
• Condensed Matter Physics
• Materials Science

Background:

• Topological protection in photonic structures offers robust unidirectional light propagation.
• Conventional designs face a trade-off between robustness and spatial footprint due to narrow guiding channels.

Purpose of the Study:

• To introduce an insulator-free topological waveguide architecture.
• To enable multi-lane unidirectional light guiding with high spatial utilization and topological protection.

Main Methods:

• Utilizing gyromagnetic honeycomb photonic crystals (PCs) with broken time-reversal and inversion symmetries.
• Achieving four photonic valley half-semimetals (PVHSMs) at critical transition boundaries.
• Arranging structures in a parallel, cyclic configuration for valley-selective guiding and topological barriers.

Main Results:

• Demonstrated an insulator-free design eliminating the robustness-footprint trade-off.
• Achieved multi-lane unidirectional light guiding with 100% spatial utilization.
• Observed densely packed, large-area one-way modes with alternating unidirectionality and robustness to sharp bends.

Conclusions:

• The proposed architecture enables ultracompact topological photonic circuits.
• This design strategy has potential for high-density integrated optics.
• The insulator-free approach overcomes limitations of conventional topological photonic waveguides.