Size Plasmon-Polariton Resonance and Its Contribution to the Giant Enhancement of the Raman Scattering

The dependence of the enhancement of the Raman scattering on the size of a dielectric column is measured in structures with the spatial modulation of the height and lateral sizes of the dielectric coated with a thick metal layer (10-80 nm). It is established that, in the case of a thick metal coating (silver, gold, and copper coatings are used) at dimensions of the dielectric column close to the laser pump wavelength, considerable enhancement of the Raman signal oscillating upon the variation of the geometrical dimensions of the structure is observed. It is shown that the observed resonance enhancement of the Raman signal is associated with the transformation of the electromagnetic radiation into localized plasmon-polariton modes, and the efficiency of such transformation is determined by the commensurability of the wavelength of the plasmon-polariton mode and the planar size of the metal film. For different metal coatings, the dependence of the enhancement of the Raman scattering on the laser wavelength is measured.