Topological Waveguiding near an Exceptional Point: Defect-Immune, Slow-Light, and Loss-Immune Propagation

Area of Science:

• Topological Photonics
• Non-Hermitian Physics
• Waveguide Engineering

Background:

• Conventional waveguides exhibit wave reflection at discontinuities and signal decay in lossy media.
• Non-Hermitian physics and topological photonics offer new paradigms for controlling wave behavior.

Purpose of the Study:

• To theoretically investigate the realization of an exceptional point between coupled topological modes in a non-Hermitian nonreciprocal waveguide.
• To explore anomalous topological wave propagation with enhanced robustness.

Main Methods:

• Exact analysis using classical Green's function theory.
• Theoretical study of coupled topological modes in a waveguide with balanced loss and gain.
• Utilizing oppositely biased gyrotropic materials.

Main Results:

• Demonstrated the possibility of an exceptional point in the proposed non-Hermitian waveguide.
• Achieved anomalous topological wave propagation near the exceptional point.
• Observed low group velocity, immunity to backscattering, and loss immunity.

Conclusions:

• Exceptional points in non-Hermitian topological waveguides enable robust wave propagation.
• This approach offers a pathway to overcome limitations of conventional wave-guiding structures.
• Potential for practical applications in realizing resilient wave propagation systems.