Abstract
We present a theory for achieving a photonic analogue of the quantum spin Hall state of electrons in
terms of a honeycomb dielectric photonic crystal where the orbital angular momentum behaves as an
emergent pseudospin degree of freedom. We show that deforming the honeycomb lattice in the way
respecting C6v lattice symmetry opens a frequency bandgap in the Dirac-like photonic dispersion
accompanied by a band inversion between the p orbital and d orbital, yielding the nontrivial photonic
topology. Experimentally we visualize the interface microwave transports between a topological
photonic crystal and a topologically trivial one both made of Al2O3, which are immune to backscattering
and robust to crystal imperfections and disorder. As only conventional dielectric materials and local
real-space manipulations are required, the present scheme can be extended to visible lights to inspire
many future applications in the field of photonics and beyond.
