Controlling light with light

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Researchers have discovered a novel technique to control light with light. The study, published in the prestigious scientific journal Nature Photonics, paves the way to the development of new optical communication technologies.

With this safer and more reliable approach, information could be encoded in the intrinsic structure of light itself, at a speed millions of times faster than current state-of-the-art technologies.

The novel technology, discovered by researchers from Politecnico di Milano, along with the Italian Institute of Technology (IIT, Genoa) and Rice University (Houston, TX), exploits artificial ultrathin materials – so-called metasurfaces.

Such metasurfaces, which are artificially designed with unique properties that are not exhibited by any naturally occurring materials, have been manufactured with advanced nanofabrication techniques by the Clean Room Facility team from IIT.

The metasurface is an ultrathin gold layer, a thousand times thinner than a human hair, where minuscule cross-shaped structures (billions per square centimetre) are crafted. When the metasurface is hit with laser pulses, its optical properties are altered significantly for a brief period of about 1 picosecond (a millionth of a millionth of a second).

During this short time window it is possible to modulate a second light beam “imprinting” bits of information in its intrinsic structure (its polarization). Such an unprecedented approach may trigger a revolution in the telecommunication systems, since it would make it possible to encode information in a light beam at ultrahigh frequencies (up to a trillion hertz) as well as to transmit it in free space in a robust and reliable fashion.

“Our discovery may allow us to send huge amounts of information over long distances with no need to install optical fibres and in a utterly safe manner with regards to both atmospheric perturbations and interceptions” – said Giuseppe Della Valle, Associate Professor at the Department of Physics of Politecnico di Milano and coordinator of the Horizon 2020 METAFAST Project.

These findings are the result of an international consortium led by Italian researchers, which involved the research groups of nanophotonics and ultrafast spectroscopy led by Professors Giuseppe Della Valle and Giulio Cerullo from the Department of Physics of Politecnico di Milano, along with the teams led by Andrea Toma and Remo Proietti at the Italian Institute of Technology in Genoa and those at Rice University in Houston (Texas, USA).

Politecnico di Milano is a scientific-technological university which trains engineersarchitects and industrial designers. The University has always focused on the quality and innovation of its teaching and research, developing a fruitful relationship with business and productive world by means of experimental research and technological transfer.