Near-field optical microscopy in the presence of an intermediate layer

The role of thin surface layers in scanning near-field optical microscopy is revealed. A theory is developed for description of the interaction between the probe of a near-field microscope and surface layers with widths much smaller than the wavelength of the incident radiation but much larger than the characteristic interatomic spacing. It is shown that, in the absence of resonance interaction between the microscope probe and the surface under study, the surface layers exert the main effect on the formation of the field in the near zone. At the same time, in the region of resonance interaction, the properties of the system are determined by the effect of both the surface layer and the semi-infinite underlying medium.