Observation of gapless corner modes in synthetic translation dimensions

TL;DR

This paper reports the experimental observation of tunable gapless corner modes in a topological photonic crystal slab under translational deformation, advancing understanding of topological phases in synthetic dimensions.

Contribution

It provides the first experimental demonstration of gapless corner modes in a photonic crystal with translational deformation, validated by near-field imaging and simulations.

Findings

Gapless corner modes are observed experimentally.

Corner modes are tunable via translational deformation.

Existence of modes is independent of corner configuration.

Abstract

The introduction of synthetic dimensions in topological photonic systems enriches the exploration of topological phase of light in higher-dimensional space beyond three-dimensional real-space. Recently, the gapless corner modes of topological photonic crystals under translational deformation have been proposed, but their experimental observation is still absent. Here, we observe the gapless corner modes in a photonic crystal slab under translational deformation. The corner mode exhibits a frequency dependence that can be tuned through the translation of the slab. Importantly, we find that the existence of gapless corner modes is independent of the specific corner configuration. The gapless corner modes are experimentally imaged via the near-field scanning measurement, and validated numerically by full-wave simulations. Our work contributes to the advancement of topological photonics and provides valuable insights into the exploration of gapless corner modes in synthetic dimensions.