Time-reversal-symmetry-protected topological photonic cavity via adiabatic interface engineering

Area of Science:

• Photonics
• Condensed Matter Physics
• Quantum Optics

Background:

• Topological optical microcavities offer robust optical field localization using protected boundary states.
• Existing designs often require external magnetic fields (gyromagnetic effects), limiting stability and on-chip integration.

Purpose of the Study:

• To present a new strategy for developing magnetic-field-free topological microcavities.
• To achieve robust optical field localization without breaking time-reversal symmetry or external fields.

Main Methods:

• Constructed a ring resonator at the adiabatic interface between a higher-order topological insulator (HOTI) lattice and a trivial insulator.
• Investigated the microcavity's performance regarding robustness against defects and whispering-gallery mode (WGM) splitting suppression.
• Demonstrated directional waveguide-microcavity-waveguide transmission using chiral excitation of topological interface states.

Main Results:

• The proposed microcavity design achieves topological protection comparable to gyromagnetic systems without external fields.
• Demonstrated robustness against defects and effective suppression of WGM splitting.
• Achieved directional transmission via chiral excitation of topological interface states.

Conclusions:

• This work introduces a novel, magnetic-field-free approach for robust topological microcavities.
• The design shows significant potential for quantum information processing and integrated photonic chips.