  Topological photonics has attracted increasing attention in recent years due
to the unique opportunities it provides to manipulate light in a robust way
immune to disorder and defects. Up to now, diverse photonic platforms, rich
physical mechanisms and fruitful device applications have been proposed for
topological photonics, including one-way waveguide, topological lasing,
topological nanocavity, Dirac and Weyl points, Fermi arcs, nodal lines, etc. In
this review, we provide an introduction to the field of topological photonics
through the lens of topological invariants and bulk-boundary correspondence in
one, two, and three dimensions, which may not only offer a unified
understanding about the underlying robustness of diverse and distinct
topological phenomena of light, but could also inspire further developments by
introducing new topological invariants and unconventional bulk-boundary
correspondence to the research of topological photonics.
