Raman systems include a radiation source, a radiation detector, and a Raman device or signal-enhancing structure. Raman devices include a tunable resonant cavity and a Raman signal-enhancing structure coupled to the cavity. The cavity includes a first reflective member, a second reflective member, and an electro-optic material disposed between the reflective members. The electro-optic material exhibits a refractive index that varies in response to an applied electrical field. Raman signal-enhancing structures include a substantially planar layer of Raman signal-enhancing material having a major surface, a support structure extending from the major surface, and a substantially planar member comprising a Raman signal-enhancing material disposed on an end of the support structure opposite the layer of Raman signal-enhancing material. The support structure separates at least a portion of the planar member from the layer of Raman signal-enhancing material by a selected distance of less than about fifty nanometers.