Photoinduced Magnetic Force Microscopy: Enabling Direct and Exclusive Detection of Optical Magnetism

TL;DR

This paper introduces a novel magnetic force microscopy technique that directly detects the magnetic component of light at the nanoscale, enabling detailed characterization of optical magnetic fields for nano-optics applications.

Contribution

It proposes a new photoinduced magnetic force microscopy method using a magnetic nanoprobe to exclusively sense optical magnetic fields at the nanoscale.

Findings

Enables direct measurement of magnetic near-fields in nano-optical devices.

Uses a magnetic nanoprobe with structured light for exclusive magnetic excitation.

Proves the feasibility of magnetic field detection independent of electric fields.

Abstract

Modern optical nano-elements pursue ever-smaller sizes and individualized functionalities. Those elements that can efficiently manipulate the magnetic field of light boast promising future applications with a great challenge: the magnetic near field is irretrievable from conventional optical far-field characterization. Here we propose photoinduced magnetic force microscopy to directly and exclusively sense the magnetic field of light at the nanoscale. The proposed instrument exploits a magnetic nanoprobe with exclusive magnetic excitation under structured light illumination. The magnetic nanoprobe detects the photoinduced magnetic force, which is defined as the dipolar Lorentz force exerted on the photoinduced magnetic dipole in the nanoprobe. Since the resulting magnetic force is proportional to the incident magnetic field, the measured force reveals the magnetic near-field distribution at the nanoscale. The proposed instrument represents a fundamental step towards comprehensive electric and magnetic near-field detection and/or manipulation in single nano-element optical devices.