title: Quantifying the magnetic nature of light emission.
abstract: Tremendous advances in the study of magnetic light-matter interactions have recently been achieved using man-made nanostructures that exhibit and exploit an optical magnetic response. However, naturally occurring emitters can also exhibit magnetic resonances in the form of optical-frequency magnetic-dipole transitions. Here we quantify the magnetic nature of light emission using energy- and momentum-resolved spectroscopy, and leverage a pair of spectrally close electric- and magnetic-dipole transitions in trivalent europium to probe vacuum fluctuations in the electric and magnetic fields at the nanometre scale. These results reveal a new tool for nano-optics: an atomic-size quantum emitter that interacts with the magnetic component of light.
authors.affiliation: Brown University, School of Engineering, Providence, Rhode Island 02912, USA.
authors.forename: Tim H
authors.initials: TH
authors.lastname: Taminiau
authors.forename: Sinan
authors.initials: S
authors.lastname: Karaveli
authors.forename: Niek F
authors.initials: NF
authors.lastname: van Hulst
authors.forename: Rashid
authors.initials: R
authors.lastname: Zia