We present theoretical and experimental studies of the reflected field in the vicinity of sub λ structures. Rigorous numerical calculations and measurements were performed to get high-precision information of certain object parameters which go beyond the limits of classical microscopy. We show that the polarization of the illumination plays a key role for the field distribution, which is reflected from the examined objects. Furthermore, we present a simplified model, which is able to qualitatively predict the behavior of the phase singularities correctly.
We present numerical calculations on the field distribution in the focus of an optical system with high numerical aperture. It is shown that a radially polarized doughnut mode fits the symmetry of the optical system and focuses down to spot sizes significantly smaller as compared to the case of linear polarization. An experimental setup to generate a radially polarized beam is presented along with a setup which is based on the knife edge method and tomographic reconstruction to measure the 3D intensity distribution in the focal region.