Monday, August 6, 2012

Quantifying the magnetic nature of light emission

In collaboration with The Institute of Photonics Sciences (ICFO) in Barcelona, Brown School of Engineering researchers in the lab of Rashid Zia ’01, Manning Assistant Professor of Engineering, have just published an article in in Nature Communications. Visiting scholar Tim Taminiau from the lab of Niek van Hulst at ICFO worked alongside Brown engineering graduate student Sinan Karaveli to demonstrate how the natural magnetic dipole transitions in lanthanide ions can be used to access optical-frequency magnetic fields.

Authors: Tim H. Taminiau, Sinan Karaveli, Niek F. van Hulst, and Rashid Zia

Examining how light emission is distributed in energy-
and momentum-space can reveal fundamental
information about optical transitions. This image
shows an energy-momentum spectrum of europium ions.
Following bright emissions lines, you may notice
several points where the contrast inverts - these
changes are direct visualizations of the opposite
symmetries of electric and magnetic dipoles transitions.
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.

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