Pseudospin-Mediated Optical Spin–Spin Interaction in Nonlinear Photonic Graphene

Abstract

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Dynamic manipulation of the spin of photons is important for many applications ranging from optical sensing to optical information processing. In the past, the study on controlling the spin of light has focused on chiral materials, three-dimensional structures lacking any mirror symmetries. However, the complexity of fabrication of such structures has hindered their practical applications. In this work, the dynamic switching of optical chirality in two-dimensional honeycomb photonic crystal—the so-called photonic graphene is explored. In particular, optical spin–spin interaction mediated by the pseudospin states of the photonic graphene is proposed. A circularly polarized pumping beam can lift the degeneracy at the Dirac cones, leading to chiral responses for a probe beam incident along the direction of the Dirac points. Interestingly, the chirality is determined by the both the valley index and the spin of the pumping beam. The proposed nonlinear photonic graphene offers a new route to manipulate valley- and spin-dependent phenomena in 2D photonic systems.