Nonlinear imaging of nanoscale topological corner states

TL;DR

This paper demonstrates the creation and observation of nanoscale topological corner states in metasurfaces, showing enhanced light localization and nonlinear effects, which could advance miniaturized photonic devices.

Contribution

It reports the first realization of nanoscale topological corner states in metasurfaces with direct imaging of localized light and nonlinear enhancement.

Findings

Observation of nanoscale topological corner states

Enhanced light-matter interactions via nonlinear imaging

Potential for miniaturized photonic device integration

Abstract

Topological states of light represent counterintuitive optical modes localized at boundaries of finite-size optical structures that originate from the properties of the bulk. Being defined by bulk properties, such boundary states are insensitive to certain types of perturbations, thus naturally enhancing robustness of photonic circuitries. Conventionally, the N-dimensional bulk modes correspond to (N-1)-dimensional boundary states. The higher-order bulk-boundary correspondence relates N-dimensional bulk to boundary states with dimensionality reduced by more than 1. A special interest lies in miniaturization of such higher-order topological states to the nanoscale. Here, we realize nanoscale topological corner states in metasurfaces with C6-symmetric honeycomb lattices. We directly observe nanoscale topology-empowered edge and corner localizations of light and enhancement of light-matter interactions via a nonlinear imaging technique. Control of light at the nanoscale empowered by topology may facilitate miniaturization and on-chip integration of classical and quantum photonic devices.