Near-field optical microscope for true surface topography: Theoretical study

We demonstrate an application of the perturbation theory based on the optical extinction theorem for the calculation of the near-field generated over a sample on a flat surface illuminated by a plane wave under total internal reflection angle. It is closely related to the theoretical modelling of a collection-mode near-field optical microscope (c-mode NOM). As an example, we calculated the near-field intensity over a semi-sphere on the flat surface. The main features of the calculated near-field are also discussed qualitatively in connection with a simple quasi-electrostatic model. On the basis of our analytical and numerical results we propose a c-mode NOM configuration which is advantageous for obtaining true surface topography.