APPLICATION OF MIE SCATTERING OF EVANESCENT WAVES TO SCANNING TUNNELING OPTICAL MICROSCOPY THEORY

In this paper we present a macroscopic theory for scanning tunnelling optical microscopy where the sample is a grating and the tip is modell ed by a dielectric sphere. The sphere is immersed in the near-field ab ove the grating and is excited by the diffracted orders which can be e vanescent. The detected signal is supposed to be the diffracted intens ity by the sphere which is calculated by using Mie theory. When studyi ng Mie scattering of one evanescent wave we show that the multipolar s eries is perturbed compared to scattering of a homogeneous wave. Even for a small sphere multipolar terms have to be taken into account. We have then proposed a formula for the intensity leading to calculations of intensity profile and surfaces and to discuss the influence of tip radius on resolution of the images.