Nonlinear second-order photonic topological insulators

TL;DR

This paper experimentally demonstrates nonlinear higher-order topological corner states and solitons in a photonic system, opening new avenues for exploring topological matter in nonlinear regimes and potential device applications.

Contribution

First experimental observation of nonlinear topological corner states and solitons in a photonic higher-order topological insulator.

Findings

Observation of nonlinear topological corner states

Formation of solitons in topological structures

Potential for nonlinear topological device applications

Abstract

Higher-order topological insulators (HOTI) are a novel topological phase beyond the framework of the conventional bulk-boundary correspondence. In these peculiar systems, the topologically nontrivial boundary modes are characterized by a co-dimension of at least two. Despite several promising preliminary considerations regarding the impact of nonlinearity in such systems, the flourishing field of experimental HOTI research has thus far been confined to the linear evolution of topological states. As such, the observation of the interplay between nonlinearity and the dynamics of higher-order topological phases in conservative systems remains elusive. In our work, we experimentally demonstrate nonlinear higher-order topological corner states. Our photonic platform enables us to observe nonlinear topological corner states as well as the formation of solitons in such topological structures. Our work paves the way towards the exploration of topological properties of matter in the nonlinear regime, and may herald a new class of compact devices that harnesses the intriguing features of topology in an on-demand fashion.