  Three-dimensional (3D) artificial metacrystals host rich topological phases,
such as Weyl points, nodal rings and 3D photonic topological insulators. These
topological states enable a wide range of applications, including 3D robust
waveguide, one-way fiber and negative refraction of surface wave. However,
these carefully designed metacrystals are usually very complex, hindering their
extension to nanoscale photonic systems. Here, we theoretically proposed and
experimentally realized an ideal nodal ring in visible region using a simple 1D
photonic crystal. The pi Berry phase around the ring is manifested by a 2pi
reflection phase's winding and the resultant drumhead surface states. By
breaking the inversion symmetry, the nodal ring can be gapped and the pi-Berry
phase would diffuse into a toroidal shaped Berry flux, resulting in photonic
ridge states (the 3D extension of quantum valley Hall states). Our results
provide a simple and feasible platform for exploring 3D topological physics and
their potential applications in nanophotonics.
