Metallic films perforated with nanoholes can support both propagating surface plasmons as well as LSPR-type resonances in the voids. (A) An isolated hole (100 nm in diameter) milled with FIB in a silver film. Image courtesy of Nathan Lindquist. (B) A random hole array in a metal film produced by colloidal lithography. (C) Schematic of periodic hole arrays in a metal film with a solid support. (D) A periodic array of nanoholes (200 nm diameter; 600 nm periodicity) milled with FIB in a gold film. Image courtesy of Hyungsoon Im.