Nature Commun. 4, 1599 (2013)

Faraday isolators are essential optical elements in communication networks and lasers, but are bulky and expensive. Nanoplasmonic systems in combination with magneto-optical materials can allow for breaking the time-reversal symmetry of light propagation when a static magnetic field is applied. Jessie Chin, Harald Giessen and colleagues in Stuttgart and Augsburg now demonstrate that a hybrid plasmonic magneto-optic device is capable of enhancing the thin-film Faraday effect by almost an order of magnitude while maintaining a high level of transparency. The researchers patterned gold nanowires on top of laser-deposited magneto-optical thin films, which showed collective oscillations of electrons and an excitation of photonic waveguide resonances with the proper polarization of the incident light. By carefully tuning the resonances of electrons and photons inside this plasmonic photonic crystal, a dramatic change in the amount of Faraday rotation was observed in the experiment. Their results may open a route for non-reciprocal thin-film devices in magnetic sensing and light modulation.