Topological photonic crystal fibers based on second-order corner modes

TL;DR

This paper introduces a novel topological photonic crystal fiber design based on second-order corner modes, revealing unique propagation properties and potential for multi-frequency transmission, expanding the scope of fiber optics applications.

Contribution

It presents a new fiber concept utilizing second-order topological corner modes from the SSH model, with tunable mode frequencies and multi-channel capabilities.

Findings

Existence of a topological bandgap at large $k_z$

Presence of two sets of corner fiber modes within the bandgap

Potential for multi-frequency and multi-channel transmission

Abstract

Photonic crystal fibers represent one of the most active research fields in modern fiber optics. The recent advancements of topological photonics have inspired new fiber concepts and designs. Here, we demonstrate a new type of topological photonic crystal fibers based on second order photonic corner modes from the Su-Schrieffer-Heeger model. Different from previous works where the in-plane properties at $k_z=0$ have been mainly studied, we find that in the fiber configuration of $k_z>0$, a topological bandgap only exists when the propagation constant $k_z$ along the fiber axis is larger than a certain threshold and the emergent topological bandgap at large $k_z$ hosts two sets of corner fiber modes. We further investigate the propagation diagrams, propose a convenient way to tune the frequencies of the corner fiber modes within the topological bandgap and envisage multi-frequency and multi-channel transmission capabilities of this new type of fibers. Our work will not only have practical importance, but could also open a new area for fiber exploration where many existing higher-order topological photonic modes could bring exciting new opportunities for fiber designs and applications.