Photoinduced Magnetic Nanoprobe Excited by Azimuthally Polarized Vector Beam

TL;DR

This paper explores how azimuthally polarized vector beams can excite magnetic nanoprobes to produce enhanced magnetic near-fields with high resolution, enabling selective magnetic excitation beyond diffraction limits.

Contribution

It introduces a novel excitation method using azimuthally polarized beams for magnetic nanoprobes, demonstrating enhanced magnetic fields and high contrast in near-field imaging.

Findings

Azimuthally polarized beams generate strong longitudinal magnetic fields.

Magnetic nanoprobes exhibit enhanced near-field with resolution beyond diffraction.

Performance metrics show superiority over other illumination methods.

Abstract

The concept of magnetic nanoprobes (or magnetic nanoantennas) providing a magnetic near-field enhancement and vanishing electric field is presented and investigated, together with their excitation. It is established that a particular type of cylindrical vector beams called azimuthally electric polarized vector beams yield strong longitudinal magnetic field on the beam axis where the electric field is ideally null. These beams with an electric polarization vortex and cylindrical symmetry are important in generating high magnetic to electric field contrast, i.e., large local field admittance, and in allowing selective excitation of magnetic transitions in matter located on the beam axis. We demonstrate that azimuthally polarized vector beam excitation of a photoinduced magnetic nanoprobe made of a magnetically polarizable nano cluster leads to enhanced magnetic near field with resolution beyond diffraction limit. We introduce two figures of merit as magnetic field enhancement and local field admittance normalized to that of a plane wave that are useful to classify magnetic nanoprobes and their excitation. The performance of magnetic nanoprobe and azimuthal polarized beams is quantified in comparison to other illumination options and with several defect scenarios.