  The interaction of light with the localized/delocalized system, i.e., a metal
surface with rectangular cavities of finite depth, has been studied. Reflection
spectrum has been measured in the optical frequencies and resonant minima have
been observed. We have developed an analytical model, which agrees well with
the experiment. The localized waveguide resonance and delocalized surface
resonance have been identified and discussed. The results may be useful for
manipulating the coupling between light and matters.
