Pseudospin induced chirality with Staggered Optical Graphene

TL;DR

This paper demonstrates how pseudospin in a photonic honeycomb lattice can couple with light's spin, inducing chirality and enabling the design of spin- or valley-selective photonic devices.

Contribution

It introduces the concept of spin-pseudospin coupling in photonic graphene analogues, revealing a new mechanism for optical chirality and device applications.

Findings

Strong spin-pseudospin coupling observed in the lattice.

Induction of optical chirality through spin-orbit conversion.

Potential for pseudospin-mediated spin or valley selective devices.

Abstract

Pseudospin plays a very important role in understanding various interesting physical phenomena associated with 2D materials such as graphene. It has been proposed that pseudospin is directly related to angular momentum, and it was recently experimentally demonstrated that orbit angular momentum is an intrinsic property of pseudospin in a photonic honeycomb lattice. However, in photonics, the interaction between spin and pseudospin for light has never been investigated. In this Letter, we propose that, in an optical analogue of staggered graphene, i.e. a photonic honeycomb lattice waveguide with in-plane inversion symmetry breaking, the pseudospin mode can strongly couple to the spin of an optical beam incident along certain directions. The spin-pseudospin coupling, caused by the spin-orbit conversion in the scattering process, induces a strong optical chiral effect for the transmitted optical beam. Spin-pseudospin coupling of light opens door to the design of pseudospin-mediated spin or valley selective photonic devices.