  Zak phase labels the topological property of one-dimensional Bloch Bands.
Here we propose a scheme and experimentally measure the Zak phase in a photonic
system. The Zak phase of a bulk band of is related to the topological
properties of the two band gaps sandwiching this band, which in turn can be
inferred from the existence or absence of an interface state. Using reflection
spectrum measurement, we determined the existence of interface states in the
gaps, and then obtained the Zak phases. The knowledge of Zak phases can also
help us predict the existence of interface states between a metasurface and a
photonic crystal. By manipulating the property of the metasurface, we can
further tune the excitation frequency and the polarization of the interface
state.
