Field enhancement analysis of an apertureless near field scanning optical micros

Plasmonic field enhancement in a fully coated dielectric near field scanning optical microscope (NSOM) probe under radial polarization illumination is analyzed using an axially symmetric three-dimensional (3D) finite element method (FEM) model. The enhancement factor strongly depends on the illumination spot size, taper angle of the probe, and the metal film thickness. The tolerance of the alignment angle is investigated. Probe designs with different metal coatings and their enhancement performa