Robust Transport of the Edge Modes along the Photonic Topological Interfaces of Different Configurations

TL;DR

This paper demonstrates how modifying the geometry of 2D photonic crystals can induce topological phase transitions, enabling robust, slow-light edge modes for advanced photonic applications.

Contribution

It introduces a scheme to achieve topological transitions in photonic crystals via geometric modifications without breaking TR symmetry.

Findings

Multiple topological phase transitions achieved by geometry modification.

Topological edge states exhibit slow light characteristics.

Edge modes are robust against defects and disorders.

Abstract

Two-dimensional photonic crystals made of six air holes on a core-shell dielectric material has been proposed to study the newly emerged photonic quantum spin Hall insulator. Specifically, radii modification of the air holes and core-shell without breaking time-reversal (TR) symmetry are supported by the C_6 point group symmetry upon a proposed scheme. It is shown that multiple topological transitions from an ordinary insulator with zero spin Chern number (Cs) to a topological insulator with a non-zero Cs can be achieved by modifying the geometry of the photonic structure. Studying the two counter-propagating helical edge modes which have the opposite group velocities are of individual importance for various optical purposes like scattering-free waveguides protected to various defects, disorders and strong light-matter interactions. We show that topological edge states demonstrate slow light characteristics. The findings emphasize the fact that exploring topological phase transition can be applied as a unique approach for realizing light transport, robust energy transportation and slow light in integrated photonic circuits and devices.