Tunable topological edge state in mirrored photonic crystal interface

Area of Science:

• Photonics
• Condensed Matter Physics
• Topological Materials

Background:

• Photonic crystals offer unique light manipulation properties.
• Topological phases in photonic systems are crucial for robust wave propagation.
• Expanded honeycomb photonic crystals (EHPCs) exhibit nontrivial band topology.

Purpose of the Study:

• To develop a novel mirrored photonic crystal interface (MPCI).
• To investigate the behavior of interface states in topologically nontrivial photonic crystals.
• To explore the potential for tunable topological edge states.

Main Methods:

• Applying a mirror operator to EHPCs.
• Adjusting geometric parameters of EHPCs to induce topological phase transitions.
• Analyzing interface states and their spin-momentum locking characteristics.

Main Results:

• A stable pair of interface states with spin-momentum locking was observed.
• Interface states were shown to close and reopen upon geometric parameter adjustment, indicating topological phase transitions.
• MPCI effectively interfaces nontrivial (C6-symmetric) and trivial (C3-symmetric) topological phases.

Conclusions:

• The MPCI demonstrates tunable topological edge states within a single photonic crystal type.
• The observed phenomena highlight the potential for creating robust transport devices.
• Findings could advance the development of photonic integrated circuits.