Valley-protected backscattering suppression in silicon photonic graphene

TL;DR

This paper investigates valley-dependent topological effects in silicon photonic graphene, demonstrating backscattering suppression at waveguide bends through valley-protected edge states and analyzing the underlying physics with a Dirac Hamiltonian.

Contribution

It introduces the concept of valley degree of freedom in silicon photonic graphene and demonstrates valley-protected backscattering suppression in all-dielectric structures.

Findings

Valley-dependent edge states are observed around Z-shape bends.

Backscattering is suppressed due to valley protection.

Topological transition is characterized by a photonic Dirac Hamiltonian.

Abstract

In this paper, we study valley degree of freedom in all dielectric silicon photonic graphene. Photonic band gap opening physics under inversion symmetry breaking is revisited by the viewpoint of nonzero valley Chern number. Bulk valley modes with opposite orbital angular momentum are unveiled by inspecting time-varying electric fields. Topological transition is well illustrated through photonic Dirac Hamiltonian. Valley dependent edge states and the associated valley-protected backscattering suppression around Z-shape bend waveguide have been demonstrated.