Experimental probe of band structures of bilayer valley photonic crystals

TL;DR

This paper experimentally investigates the band structures of bilayer valley photonic crystals, revealing how layer stacking influences topological edge modes and offering insights into bilayer topological insulators.

Contribution

It provides the first experimental imaging of bilayer valley photonic crystal band structures with different stacking configurations and observes topological edge modes induced by topology.

Findings

Distinct bulk band structures for different stacking configurations

Observation of topological edge modes in bilayer systems

Layer degree of freedom acts as a pseudospin for light control

Abstract

Research on two-dimensional van der Waals materials has demonstrated that the layer degree of freedom can significantly alter the physical properties of materials due to the substantial modification of bulk bands. Inspired by this concept, layered photonic systems have been proposed and realized, revealing novel phenomena absent in their monolayer counterparts. In this work, we experimentally investigate the band structures of bilayer valley photonic crystals. Two typical structures with different stacking configurations are experimentally imaged via the near-field scanning technology, exhibiting distinct bulk band structures. Furthermore, different topological edge modes induced by distinct topology are observed, revealing that the layer degree of freedom can be regarded as a pseudospin and offer further capabilities for controlling the flow of light. Our work not only elucidates the evolution of band structures from monolayer to bilayer topological systems but also provides an experimental platform for the further exploration of bilayer topological insulators.