Super scattering: Physicists at the University of Graz overcome the limit of light scattering at the nanoscale

A silicon nanoparticle (red cylinder), is illuminated by laser light (purple arrow). As a result of super scattering, the nanoparticle redirects a large portion of the incoming laser across multiple directions (white arrows). Image: Adrià Canós Valero

Being able to control light at the nanoscale is a prerequisite for many technological and scientific applications in telecommunications, sensing or modern biology. In all these applications, the scattering of light by nanoparticles made of metals or semiconductors plays a decisive role. However, there is a physical limit that restricts light scattering by nanoparticles and thus the efficiency of technological devices: the so-called single-channel limit. Efforts to overcome it date back to decades ago, with very little success. Now, physicists from the University of Graz in collaboration with an international team of researchers have found out how this limit can be exceeded. This opens new technological possibilities.

“We have discovered a mechanism that turns nanoparticles into super scatterers,” reports Adrià Canós Valero, first author of the publication, which appeared in the research journal Nature Communications. “The shape and dimensions of the particles are crucial. When a laser hits a nanoparticle, part of the light is scattered. The new process we discovered allows, just by designing particles of a certain size and shape, to control the properties of the light – that is, how much is scattered, in which directions and which wavelengths.”

The inspiration for the effect came from an unexpected source. “There are also nanostructures in which light remains trapped and is not scattered. We realized that if we break such structures by changing their size and shape and release the light, a new type of resonance is created – a vibration that scatters light very strongly, even beyond the single-channel limit. We call such oscillations super-dipole resonances,” explains Thomas Weiss, head of the Theoretical Nanophysics group at the University of Graz.
In an experiment with microwaves, the researchers have already demonstrated how super-scattering nanoparticles work. Soon they should also succeed with visible light.

Publication
Superscattering Emerging from the Physics of Bound States in the Continuum
Adrià Canós Valero, Hadi K. Shamkhi, Anton S. Kupriianov, Thomas Weiss, Alexander A. Pavlov, Dmitrii Redka, Vjaceslavs Bobrovs, Yuri Kivshar and Alexander S. Shalin
Nature Communications
https://www.nature.com/articles/s41467-023-40382-y

Gudrun Pichler

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