Optical interaction between a dielectric tip and a nanometric lattice: implications for near-field microscopy

Abstract

We make a theoretical analysis of the interaction of the field transmitted by a subwavelength tip and a two-dimensional subwavelength lattice. Such a model provides a new insight into the resolution achievable by near-field microscopy and confirms the experimental results obtained recently. In the present model the probe, characterized by its electric dipolar susceptibility, is assumed to be locally spherical, and the representation of the sample is based on a discrete description of the matter. This permits separation of the electric field detected by the probe after reflection into two different parts that describe both the continuum character and the corrugation of the surface. Numerical results performed on a two-dimensional lattice are similar to those obtained by atomic force microscopy and exhibit specific behavior such as a strong dependence on the polarization of the incident field.