Various aspects of the prsent invention are directed to electric-field-enhancement structures (100) and detection apparatuses (600, 700, 800) that employ such electric-field-enhancement structures. In one aspect of the present invention, an electric-field-enhancement structure (100) includes a substrate (102) having a surface (104). The substrate (102) is capable of supporting a planar mode (114) having a planar-mode frequency. A plurality of nanofeatures (106) is associated with the surface (104), and each of nanofeatures (106) exhibits a localized-surface-plasmon mode (116) having a localized-surface-plasmon frequency approximately equal to the planar-mode frequency.