Effect of polarization direction on the electric field distribution at the near-field of a tip-on-aperture near-field scanning optical microscope probe

A tip-on-aperture (TOA) probe is a novel near-field scanning optical microscope (NSOM) probe, which combines the features of aperture and apertureless probes. It has a small metallic tip at the end of an aperture NSOM's probe. The tip is illuminated through an aperture at the near field of the probe and electromagnetic interaction between the structured sharp tip at the end of the probe and the surface is used for measurements and materials processing. In this study, the electric field distributions at the near-field of a TOA probe were calculated numerically to analyze the effects of polarization direction on the characteristics of measurement and processing. A TOA probe is asymmetric for the axis, since it has a probe at metal coated layer on the aperture. The geometrical relationship between this asymmetric shape and polarization direction is the reason for the change of the electromagnetic energy distributions. Numerical analysis shows that a TOA probe can make the best use of the tip for high resolutions when the tip is located on the parallel axis with the polarization direction.