  This colloquium analyzes the interaction of light with two-dimensional
periodic arrays of particles and holes. The enhanced optical transmission
observed in the latter and the presence of surface modes in patterned metal
surfaces are thoroughly discussed. A review of the most significant discoveries
in this area is presented first. A simple tutorial model is then formulated to
capture the essential physics involved in these phenomena, while allowing
analytical derivations that provide deeper insight. Comparison with more
elaborated calculations is offered as well. Finally, hole arrays in
plasmon-supporting metals are compared to perforated perfect conductors, thus
assessing the role of plasmons in these types of structures through analytical
considerations.
