# Photonic crystal nanocavity based on a topological corner state

## TL;DR

This paper demonstrates a topological photonic crystal nanocavity based on a corner state, achieving high localization and quality factor, advancing nanoscale photonic device development.

## Contribution

It introduces a novel topological corner state nanocavity in photonic crystals, supported by hierarchical bulk-edge and edge-corner correspondences.

## Key findings

- Observed a localized corner mode with high Q factor over 2000
- Verified the nanocavity's potential for integrated photonic circuits
- Demonstrated hierarchical topological state support

## Abstract

Topological phonics has emerged as a novel approach to engineer the flow of light and provides unprecedented means for developing diverse photonic elements, including robust optical waveguides immune to structural imperfections. However, the development of nanoscale standing-wave cavities in topological photonics is rather slow, despite its importance when building densely-integrated photonic integrated circuits. In this Letter, we report a photonic crystal nanocavity based on a topological corner state, supported at a 90-degrees-angled rim of a two dimensional photonic crystal. A combination of the bulk-edge and edge-corner correspondences guarantees the presence of the higher-order topological state in a hierarchical manner. We experimentally observed a corner mode that is tightly localized in space while supporting a high Q factor over 2,000, verifying its promise as a nanocavity. These results cast new light on the way to introduce nanocavities in topological photonics platforms.

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Source: https://tomesphere.com/paper/1812.10171