Rapid simulations of hyperspectral near-field images of three-dimensional heterogeneous surfaces - part II

The modeling of the near-field interaction in the scattering-type scanning near-field optical microscope (s-SNOM) is rapidly advancing, although an accurate yet versatile modeling framework that can be easily adapted to various complex situations is still lacking. In this work, we propose a time-efficient numerical scheme in the quasi-electrostatic limit to capture the tip-sample interaction in the near field. This method considers an extended tip geometry, which is a significant advantage compared to the previously reported method based on the point-dipole approximation. Using this formalism, we investigate, among others, nontrivial questions such as uniaxial and biaxial anisotropy in the near-field interaction, the relationship between various experimental parameters (e.g. tip radius, tapping amplitude, etc.), and the tip-dependent spatial resolution. The demonstrated method further sheds light on the understanding of the contrast mechanism in s-SNOM imaging and spectroscopy, while also representing a valuable platform for future quantitative analysis of the experimental observations. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

The modeling of near-field interaction in scattering-type scanning near-field optical microscope (s-SNOM) is rapidly advancing, but a versatile and accurate modeling framework for various complex situations is still lacking. In this work, a time-efficient numerical scheme in the quasi-electrostatic limit is proposed to capture the tip-sample interaction in the near field. The method considers an extended tip geometry, providing an advantage compared to the previously reported methods. Through investigating anisotropy, experimental parameters, and spatial resolution, the method contributes to the understanding of the contrast mechanism in s-SNOM imaging and spectroscopy and provides a valuable platform for future quantitative analysis of experimental observations.