Frequency tunable topological edge states of two-dimensional honeycomb lattice photonic crystals

TL;DR

This paper demonstrates frequency tunable topological edge states in 2D honeycomb photonic crystals, enabling unidirectional light transmission with adjustable frequency ranges through shape modifications of scatterers.

Contribution

It introduces a method to tune the frequency of topological edge states in 2D honeycomb photonic crystals by altering scatterer shapes, enhancing control over topological photonic devices.

Findings

Topological edge states are realized in 2D honeycomb photonic crystals.

Frequency of edge states can be significantly tuned by changing scatterer shapes.

Unidirectional transmission is robust against various defects and bends.

Abstract

In this paper, the photonic quantum spin Hall effect (PQSHE) is realized in dielectric two-dimensional (2D) honeycomb lattice photonic crystal (PC) by stretching and shrinking the honeycomb unit cell. Combining two honeycomb lattice PCs with a common photonic band gap (PBG) but different band topologies can generate a topologically protected edge state at the combined junction. The topological edge states and their unidirectional transmission as the scatterers with triangular, pentagonal, and heptagonal shapes are researched. Meanwhile, the unidirectional transmission in an inverted {\Omega}-shaped waveguide with large bending angle is realized, and verifies the characteristics of the topological protection by adding different kind of defects. Moreover, the frequency varies significantly when changing the scatterers shape, which shows that the PC with various scatterers shape can tune the frequency range of the topological edge state significantly. In other words, it can adjust the frequency of unidirectional transmission and increase the adjustability of the topological edge state.