Efficient light coupling between conventional silicon photonic waveguides and quantum valley-Hall topological...

Area of Science:

• Photonics
• Condensed Matter Physics
• Materials Science

Background:

• Efficient light coupling is essential for integrating quantum valley-Hall (QVH) topological interfaces into 2D optical chips.
• Current direct coupling methods suffer from low transmission efficiency (<50%) due to back-reflections and scattering.

Purpose of the Study:

• To numerically demonstrate efficient light coupling between QVH topological interfaces and silicon photonic waveguides.
• To enhance light transmission for practical on-chip 2D topological photonic devices.

Main Methods:

• Numerical simulation of light coupling between QVH interfaces and silicon waveguides.
• Introduction of photonic crystal line defects as a buffering layer.
• Analysis of transmission efficiency and mode profile conversion.

Main Results:

• Direct end-butt coupling yielded <50% transmission efficiency.
• Introducing photonic crystal line defects increased transmission efficiency to 95.8% (bridge QVH) and 94.3% (zigzag QVH).
• Buffering line defect modes facilitated mode profile conversion between interface and waveguide modes.

Conclusions:

• Photonic crystal line defects significantly enhance light coupling efficiency for QVH topological interfaces.
• The proposed method offers a practical and fabrication-friendly approach for on-chip 2D topological photonics.
• This design serves as a guide for future implementations of topological photonic devices.