For those who came in late, plasmon nanojets enable nanoscale focusing of light and, theoretically, allows engineers to bypass one of the fundamental limitations of the ordinary converging lens.

Tight compression of light waves is necessary to use them as signal carriers in compact devices that would work much faster than today's electronics.

The idea is that by replacing electrons in microcircuits with photons -- the massless particles of light -- the resulting devices would operate much faster.

What stops this happening is that photonic gear would be huge and to make them smaller, engineers require a way to control photons on such a small scale that the light wave itself has to be localised, squeezed into a minimum space.

Ideally, the light needs to be focused into a spot smaller than half of the original wavelength. While this feat is impossible in the classical optics due to what is known as the diffraction limit, modern research has already found several ways around it. And the newly observed plasmon nanojet is likely to become one of them.

The team has created a focusing component, or nanolens, capable of converting light into electromagnetic waves of a special kind, compressing it to 60 per cent of the initial radiation wavelength. This new contraption is made up of a square piece of dielectric material 5 by 5 micrometers in size and 0.25 micrometers thick. Shown in figure 1, the square particle lies on a thin 0.1-micrometer gold film, next to an etched grating that diffracts light.

The paper's lead author, Professor Igor Minin of Tomsk Polytechnic University said that one of the mechanisms that enable subwavelength focusing relies on the plasmon nanojet, a phenomenon we have observed in an experiment for the first time.

Study co-author Dmitry Ponomarev said that using computer simulations, the team figured out the appropriate dimensions of the dielectric particle and the diffraction grid in gold film.

“When these parameters are right, SPPs have different phase velocities at different points in the particle. This causes the wavefront to bend, creating a vortex in the particle and therefore a region dense with SPPs behind it, which we call a plasmon nanojet," he said.

The head of the MIPT Center for Photonics and 2D Materials, Valentyn Volkov, who co-authored the study, added: "The experimental observation of plasmon nanojets has been made possible by a concerted effort on the part of our center's researchers and the colleagues in Moscow, Tomsk, and Copenhagen. This collaboration is not over, and we are planning to show other exciting effects that have to do with the formation, propagation, and application of plasmon nanojets."