  The recent research of topological photonics has not only proposed and
realized novel topological phenomena such as one-way broadband propagation and
robust transport of light, but also designed and fabricated photonic devices
with high-performance indexes which are immune to fabrication errors such as
defects or disorders. Photonic crystals, which are periodic optical structures
with the advantages of good light field confinement and multiple adjusting
degrees of freedom, provide a powerful platform to control the flow of light.
With the topology defined in the reciprocal space, photonic crystals have been
widely used to reveal different topological phases of light and demonstrate
topological photonic functionalities. In this review, we present the physics of
topological photonic crystals with different dimensions, models and topological
phases. The design methods of topological photonic crystals are introduced.
Furthermore, we review the applications of topological photonic crystals in
passive and active photonics. These researches pave the way of applying
topological photonic crystals in practical photonic devices.
