Spatial resolution beyond the Rayleigh limit

The spatial resolution problem connected to light scattering from mesoscopic objects and nanostructures is studied theoretically using various electromagnetic propagator formalisms. It is shown that the spatial domain occupied by the transverse part of the microscopic current density induced by the incident field in the scatterer is the source domain of the radiative part of the scattered field. In radiative near-field scattering processes the relative positions of two mesoscopic (or microscopic) objects placed in each other's transverse current density domains cannot be resolved. In electric-dipole scattering these domains overlap once the non-radiative dipole-dipole interaction becomes of importance. Although microscopic electrodynamics basically is needed in a quantitative analysis, it appears that a macroscopic vectorial theory which includes both polarization and magnetization in the scatterer qualitatively can capture important aspects of the spatial resolution problem. It is predicted that spatial (super) resolution on the atomic length scale might be possible in near-field scattering processes where only the spin dynamics of the scatterer is involved. This prediction is illustrated by studies of the Dirac spin current density and long-wavelength scattering from nonrelativistic spin-1/2 dynamics.