Generalized Mie theory for full-wave numerical calculations of scattering near-field optical microscopy with arbitrary geometries

TL;DR

This paper introduces a comprehensive electrodynamic method based on generalized Mie theory for calculating near-field optical scattering in arbitrary geometries, surpassing previous quasi-electrostatic approximations.

Contribution

It presents a fully electrodynamic approach for near-field contrast calculation applicable to complex, arbitrary configurations of scatterers, expanding beyond axisymmetric models.

Findings

Successfully models coupling of hyperbolic phonon polaritons in hexagonal boron nitride

Demonstrates enhanced scattering in core-shell systems

Accurately reproduces spatial near-field maps

Abstract

Scattering-type scanning near-field optical microscopy is becoming a premier method for the nanoscale optical investigation of materials well beyond the diffraction limit. A number of popular numerical methods exist to predict the near-field contrast for axisymmetric configurations of scatterers on a surface in the quasi-electrostatic approximation. Here, a fully electrodynamic approach is given for the calculation of near-field contrast of several scatterers in arbitrary configuration, based on the generalized Mie scattering method. Examples for the potential of this new approach are given by showing the coupling of hyperbolic phonon polaritons in hexagonal boron nitride layers and showing enhanced scattering in core-shell systems. In general, this method enables the numerical calculation of the near-field contrast in a variety of strongly resonant scatterers and is able to accurately recreate spatial near-field maps.