Macroscopic self-consistent model for external-reflection near-field microscopy

The self-consistent macroscopic approach based on the Maxwell equations in two-dimensional geometry is developed to describe tip–surface interaction in external-reflection near-field microscopy. The problem is reduced to a single one-dimensional integral equation in terms of the Fourier components of the field at the plane of the sample surface. This equation is extended to take into account a pointlike scatterer placed on the sample surface. The power of light propagating toward the detector as the fiber mode is expressed by using the self-consistent field at the tip surface. Numerical results for trapezium-shaped tips are presented. We show that the sharper tip and the more confined fiber mode result in better resolution of the near-field microscope. Moreover, it is found that the tip–surface distance should not be too small so that better resolution is ensured.