Nature Commun. 3, 979 (2012)

Light is intrinsically a combination of electric and magnetic fields. But when photons interact with matter, it is usually the electric interactions that play the dominant role, almost totally obscuring any magnetic effects. Tim Taminiau and co-workers, however, have managed to separate the influence of magnetic and electric dipoles in europium ions, and then to probe magnetic light–matter interactions at the nanoscale.

Emission from an electric and a magnetic dipole differ in terms of their shape and polarization. The ions investigated by Taminiau et al. were scattered throughout a dielectric thin film. Interference effects due to scattering at the top and bottom surfaces of the film further enhanced the differences between electric and magnetic optical transitions, making them distinguishable in energy- and momentum-resolved measurements.

The researchers hope that this technique could become an important tool for nano-optics. They show how it can be used to investigate the changes in the electromagnetic environment as different materials are placed on top of the dielectric thin film.