# Probing Optical Magnetic Dipole Transitions in Eu3+ Using Structured Light and Nanoscale Sample Engineering

## TL;DR

This paper introduces a method to enhance the study of magnetic dipole transitions in Eu3+ ions using structured light and nanoscale engineering.

## Contribution

The novel approach combines structured light and tailored sample morphology to enable high-contrast magnetic dipole excitation.

## Key findings

- Azimuthally polarized beams enhance magnetic dipole transitions 3.0–4.5 times more than other beam types.
- The method allows for selective excitation of both magnetic and electric dipole transitions in Eu3+:Y2O3 nanostructures.
- Metallic antennas integrated with nanostructures improve the spectroscopy of forbidden transitions.

## Abstract

At optical frequencies, interactions of the electric
field component
of light with matter dominate, whereas magnetic dipole transitions
are inherently weak and challenging to access independently of electric
dipole transitions. However, magnetic dipole transitions are of interest,
as they can provide valuable complementary information about the matter
under investigation. Here, we present an approach which combines structured
light irradiation with tailored sample morphology for enhanced and
high-contrast optical magnetic field excitation, and we test this
technique on Eu3+ ions. We generate spectrally tunable,
narrowband, polarization-shaped ultrashort laser pulses, which are
specifically optimized for the spectral and the spatial selective
excitation of magnetic dipole and electric dipole transitions in Eu3+:Y2O3 nanostructures integrated into
a metallic antenna. In the presence of the metallic antenna, the excitation
with an azimuthally polarized beam is shown to provide at least a
3.0–4.5-fold enhancement of the magnetic dipole transition
as compared to a radially polarized beam or a conventional Gaussian
beam. Thus, our setup provides new opportunities for the spectroscopy
of forbidden transitions.