Valley-contrasting orbital angular momentum in photonic valley crystals

TL;DR

This paper demonstrates valley-contrasting orbital angular momentum in dielectric photonic crystals, enabling selective excitation and robust, broadband valley-dependent edge states for potential applications in topological photonics.

Contribution

It introduces valley-contrasting orbital angular momentum in photonic valley crystals and shows how to achieve valley-selective excitation and robust edge states without complex boundary optimization.

Findings

Selective excitation of valley chiral states using orbital angular momentum sources.

Broadband robust transmission along zigzag boundaries.

Suppression of inter-valley scattering in photonic valley crystals.

Abstract

Valley, as a degree of freedom, has been exploited to realize valley-selective Hall transport and circular dichroism in two-dimensional layered materials. On the other hand, orbital angular momentum of light with helical phase distribution has attracted great attention for its unprecedented opportunity to optical communicagtions, atom trapping, and even nontrivial topology engineering. Here, we reveal valley-contrasting orbital angular momentum in all-dielectric photonic valley crystals. Selective excitation of valley chiral bulk states is realized by sources carrying orbital angular momentum with proper chirality. Valley dependent edge states, predictable by nonzero valley Chern number, enable to suppress the inter-valley scattering along zigzag boundary, leading to broadband robust transmission in Z-shape bend without corner morphological optimization. Our work may open up a new door towards the discovery of novel quantum states and the manipulation of spin-orbit interaction of light in nanophotonics.