Spectroscopic study of resonant dielectric structures in near-field

Gratings can be considered as resonant structures in near-field. The enhancement of the intensity recorded by Scanning Near-Field Optical Microscopes (SNOM) is due to interferences in relation with the ratio of the wavelength to the product of the optical index by the period of the grating. We discuss the effect of this ratio (in the range 0.9, 1.1) on the intensity patterns. The influence of the polarization on near-field data is analyzed in both theoretical computations and experimental result.