Observation of unidirectional soliton-like edge states in nonlinear Floquet topological insulators

TL;DR

This paper reports the experimental observation of unidirectional soliton-like edge states in nonlinear photonic topological insulators, revealing how topological edge states behave under nonlinearity and interactions.

Contribution

It demonstrates for the first time the formation of soliton-like edge states in nonlinear photonic topological insulators due to Kerr nonlinearity.

Findings

Observation of unidirectional soliton-like edge states

Non-diffracting coherent wavepackets on the edge

Power radiation due to system gaplessness

Abstract

A salient feature of solid-state topological materials in two dimensions is the presence of conducting electronic edge states that are insensitive to scattering by disorder. Such unidirectional edge states have been explored in many experimental settings beyond solid-state electronic systems, including in photonic devices, mechanical and acoustic structures, and others. It is of great interest to understand how topological states behave in the presence of inter-particle interactions and nonlinearity. Here we experimentally demonstrate unidirectional soliton-like nonlinear states on the edge of photonic topological insulators consisting of laser-written waveguides. As a result of the optical Kerr nonlinearity of the ambient glass, the soliton-like wavepacket forms a non-diffracting coherent structure that slowly radiates power because of the intrinsic gaplessness of the system. The realization of soliton-like edge states paves the way to an understanding of topological phenomena in nonlinear systems and those with inter-particle interactions.