Chiral topological whispering gallery modes formed by gyromagnetic photonic crystals

TL;DR

This paper demonstrates a novel topological photonic cavity supporting chiral whispering gallery modes in gyromagnetic photonic crystals, which are robust against defects and disorder, promising for resilient optical device design.

Contribution

It introduces a topological cavity supporting chiral whispering gallery modes formed by gyromagnetic photonic crystals, highlighting their robustness and potential for optical applications.

Findings

Existence of discrete edge states in the topological band gap.

Modes are immune to defects and disorder.

Supports purely traveling, unidirectional modes.

Abstract

We explore a hexagonal cavity that supports chiral topological whispering gallery (CTWG) modes, formed by a gyromagnetic photonic crystal. This mode is a special type of topologically protected optical mode that can propagate in photonic crystals with chiral direction. Finite element method simulations show that discrete edge states exist in the topological band gap due to the coupling of chiral edge states and WG modes. Since the cavity only supports edge state modes with group velocity in only one direction, it can purely generate traveling modes and be immune to interference modes. In addition, we introduced defects and disorder to test the robustness of the cavity, demonstrating that the CTWG modes can be effectively maintained under all types of perturbations. Our topological cavity platform offers useful prototype of robust topological photonic devices. The existence of this mode can have important implications for the design and application of optical devices.