Metastructures for the giant enhancement of Raman scattering in the near infrared spectral range

The properties of periodic dielectric structures coated with a thick metal layer, which allow enhancing an inelastic light scattering signal by more than eight orders of magnitude at a laser pump wavelength of 1064 nm, have been studied. It has been shown that the giant resonance enhancement of the Raman signal in the near infrared range is ensured by additionally enhanced plasma resonance and by geometrical resonance between the sizes of the dielectric structure and the wavelength of laser radiation. The dependence of the enhancement factor of the Raman scattering on the height of columns in periodic dielectric structures, as well as the dependence of the enhancement factor on the thickness of the metallic coating, has been studied. New resonance modes have been revealed, for which the height of dielectric columns is 1/4, 1/2, and 3/4 of the wavelength of laser radiation. It has been shown that record high enhancement factors of the Raman scattering can be reached in the near infrared range, which is also due to a high $Q$ factor of plasma waves in metals at these frequencies.