NEW OUTCOME
14/01/2011
FUNCOAT: Instituto de Microelectrónica de Madrid (IMM-CSIC) co-develops a new family of optical nanodevices based on surface plasmons.
Surface plasmons allow confining light in regions of nanometric dimensions, well below those usually allowed by Optics (much smaller than the light wavelength). Unfortunately, most plasmonic systems are “passive”, since their properties cannot be modified once fabricated.
In this work, the insertion of a thin ferromagnetic cobalt layer allows controlling the plasmonic properties of the system by the application of a magnetic field of relatively low magnitude. In particular, the involved research groups fabricated “magneto-plasmonic” micro-interferometers with which it has been possible to demonstrate the magnetic modulation of the surface plasmons wave vector. This opens a route for the development of active magneto-plasmonic devices with relevance for example in sensing and communications.
This work has been published in February 2010 in Nature Photonics
The figure shows a sketch and an electron microscope image of a magnetoplasmonic micro interferometer. It consist of a 200 nm thick gold/cobalt/gold trilayer in which a slit and a groove of nanometric dimensions have been sculptured by a focused beam of gallium ions.
The working principle of the device is very simple: upon illumination, photons shining the groove excite surface plasmons that propagate towards the slit. Once in the slit, these plasmons transform into photons that are emitted on the other side (glass substrate) of the structure. These emitted photons interfere with those that pass directly through the slit. The intensity of the light passing through the slit depends on the phase difference of direct and Plasmon generated photons. A magnetic field allows controlling the wave vector of the surface plasmons and, therefore, the phase difference between these two kinds of photons.
