Near-field optical effects inside a photosensitive sample coupled with a SNOM tip

In this paper, we report a series of two-dimensional computerized simulations to gain more insight in the mechanisms responsible for near-field optical nanolithography (NFONL). Several significant factors are considered successively, e.g., the kind of tip used to illuminate the photosensitive sample (purely dielectric or coated tips), and the polarization of the incident electromagnetic field. A comparative study of the near fields generated by bulk dielectric and metallized tips is important to determine their relative capability as efficient tools for nanoindentation. In the same manner, the role of the tip–sample spacing during the exposure of the sample has also to be assessed to get a better control of the resulting nanoindentation patterns. Finally, a simultaneous study of both s- and p-polarizations is mandatory if we want to interpret recent experimental data issued from standard three-dimensional devices. With the help of these simulations, we explain some typical effects encountered during nanoindentation experiments realized with a reflection SNOM architecture.