Observation and control of nonlinear electromagnetic topological edge states

TL;DR

This paper experimentally demonstrates nonlinear spectral tuning of electromagnetic topological edge states in coupled resonators, revealing how edge states can be controlled and transformed through nonlinear effects in a pump-probe setup.

Contribution

It presents the first experimental observation of nonlinear self-induced spectral tuning of topological edge states in photonic resonator arrays.

Findings

Spectral shifts mainly affect edge modes in weak nonlinearity.

Strong pumping causes edge state transformation and hybridization with bulk modes.

Predicted transition from topological to unstable regimes under parametric driving.

Abstract

Topological photonics has recently emerged as a route to realize robust optical circuitry, and nonlinear effects are expected to enable tunability of topological states with the light intensity. Here we realize experimentally nonlinear self-induced spectral tuning of the electromagnetic topological edge states in an array of coupled nonlinear resonators in a pump-probe experiment. In a weakly nonlinear regime, we observe that resonators frequencies exhibit spectral shifts, that are concentrated mainly at the edge mode affecting only weakly the bulk modes. For a strong pumping, we describe several scenarios of the transformation of the edge states and their hybridization with bulk modes, and also predict a parametrically driven transition from topological to unstable regimes.