Topological dipole Floquet solitons

TL;DR

This paper introduces a new type of topological dipole solitons in Floquet topological insulators based on kagome waveguide arrays, highlighting their unique spectral properties and stability.

Contribution

It presents the theoretical prediction and numerical demonstration of topological dipole solitons bifurcating from edge states in a kagome array, a novel phenomenon in topological photonics.

Findings

Dipole solitons bifurcate from two edge states in different topological gaps.

Such solitons can propagate stably over hundreds of helix periods.

Edge states have nearly vanishing group velocities and same sign of dispersion.

Abstract

We theoretically introduce a new type of topological dipole solitons propagating in a Floquet topological insulator based on a kagome array of helical waveguides. Such solitons bifurcate from two edge states belonging to different topological gaps and have bright envelopes of different symmetries: fundamental for one component, and dipole for the other. The formation of dipole solitons is enabled by unique spectral features of the kagome array which allow the simultaneous coexistence of two topological edge states from different gaps at the same boundary. Notably, these states have equal and nearly vanishing group velocities as well as the same sign of the effective dispersion coefficients. We derive envelope equations describing components of dipole solitons and demonstrate in full continuous simulations that such states indeed can survive over hundreds of helix periods without any noticeable radiation into the bulk.