Capabilities and limitations of paraxial operator approach for modeling of nano-scale feature evaluation

The interaction of light with nano-scale features is usually associated with rigorous vector modeling or other computation intensive method. It turns out, however, that several interesting cases can be analyzed by a model based on scalar, paraxial operators. Good correspondence was found between this theoretical model and experimental investigation. In our work, the capabilities of scalar, paraxial operator approach are discussed for the cases of Dark beam and Gaussian beam scanning microscopes. Fundamental limitations of the approach are outlined as well. The sensitivity of the Dark beam scanning microscope was compared for the real experimental procedure and the idealized theoretical model which indicated a potential of 1nm sensitivity.