Various aspects of the present invention are directed to electric-field-enhancement structures and detection apparatuses that employ such electric-field-enhancement structures. In one aspect of the present invention, an electric-field-enhancement structure includes a substrate having a surface. The substrate is capable of supporting a planar mode having a planar-mode frequency. A plurality of nanofeatures is associated with the surface, and each of nanofeatures exhibits a localized-surface-plasmon mode having a localized-surface-plasmon frequency approximately equal to the planar-mode frequency.