$\pi$-solitons on a ring of waveguides

TL;DR

This paper investigates the existence, stability, and properties of novel $ ext{pi}$-solitons in a ring of oscillating waveguides with topological features, revealing new in-phase and out-of-phase modes influenced by ring size and spacing.

Contribution

It introduces the concept of $ ext{pi}$-solitons in a Floquet topological ring waveguide system and analyzes their stability and dependence on geometric parameters.

Findings

Emergence of anomalous topological $ ext{pi}$-modes at the ring ends

Formation of in-phase and out-of-phase $ ext{pi}$-modes

Stability of solitons depends on ring size and spacing

Abstract

We study the existence and stability of $\pi$-solitons on a ring of periodically oscillating waveguides. The array is arranged into Su-Schrieffer-Heeger structure placed on a ring, with additional spacing between two ends of the array. Due to longitudinal oscillations of waveguides, this Floquet structure spends half of the longitudinal period in topological phase, while on the other half it is nontopological. Nevertheless, waveguide oscillations lead to the emergence of anomalous topological $\pi$-modes at both ends of the structure that strongly couple in our ring geometry, leading to the formation of previously unexplored in-phase and out-of-phase $\pi$-modes. We study topological solitons bifurcating from such linear $\pi$-modes and demonstrate how their properties and stability depend on the size of the ring and on spacing between two ends of the array.