Image formation properties and inverse imaging problem in aperture based scanning near field optical microscopy

TL;DR

This paper develops a methodology to solve the inverse imaging problem in aperture-based SNOM, enabling the retrieval of vectorial electric and magnetic field components from polarization- and phase-resolved measurements, and explains how probe design influences field sensitivity.

Contribution

The paper introduces a novel approach to reconstruct vectorial light fields in aperture SNOM and explains how probe parameters affect electric and magnetic field detection.

Findings

Method to retrieve vectorial field components from measurements

Analysis of probe geometry and material effects on imaging

Design guidelines for probes sensitive to specific field components

Abstract

Aperture based scanning near field optical microscopes are important instruments to study light at the nanoscale and to understand the optical functionality of photonic nanostructures. In general, a detected image is affected by both, the transverse electric and magnetic field components of light. The discrimination of the individual field components is challenging, as these four field components are contained within two signals in the case of a polarization-resolved measurement. Here, we develop a methodology to solve the inverse imaging problem and to retrieve the vectorial field components from polarization- and phase-resolved measurements. Our methodology relies on the discussion of the image formation process in aperture based scanning near field optical microscopes. On this basis, we are also able to explain how the relative contributions of the electric and magnetic field components within detected images depend on the probe geometry, its material composition, and the illumination wavelength. This allows to design probes that are dominantly sensitive either to the electric or magnetic field components of light.