Mapping Nanoscale Electromagnetic Near-Field Distributions Using Optical Forces

TL;DR

This paper introduces an AFM-based optical force microscopy technique capable of mapping nanoscale electromagnetic near-fields with high resolution, validated through experiments with laser beams and nanoparticles, enabling detailed optical field imaging.

Contribution

The paper presents a novel method for mapping optical near-fields at the nanoscale using AFM-based force measurements, validated against theoretical models and applicable to various optical phenomena.

Findings

High-resolution near-field maps match theoretical predictions.

Technique works with different polarizations and wavelengths.

Allows background-free, thermal noise-limited optical imaging.

Abstract

We demonstrate the application of Atomic Force Microscopy (AFM) based optical force microscopy to map the optical near-fields with nanometer resolution, limited only by the AFM probe geometry. We map the electric field distributions of tightly focused laser beams with different polarizations and show that the experimentally measured data agrees well with the theoretical predictions from a dipole-dipole interaction model, thereby validating our approach. We further validate the proposed technique by evaluating the optical electric field scattered by a spherical nanoparticle by measuring the optical forces between the nanoparticle and gold coated AFM probe. The technique allows for wavelength independent, background free, thermal noise limited mechanical imaging of optical phenomenon with sensitivity limited by AFM performance. Optical forces due to both electric and magnetic dipole-dipole interactions can be measured using this technique.