Show/hide main menu


News Highlights

Optical 'watermills' control spinning light

Posted on 13/11/2014

Scientists at King’s have built on research they conducted last year to achieve previously unseen levels of control over the travelling direction of electromagnetic wave in waveguides and proved that the process works equally well in reverse, opening up the way for the development of technologies that could revolutionise secure communications as well as high speed computing.

In a paper published today in Nature Communications the team demonstrates that light waves propagating along a surface will induce the spinning of electrons in a nearby nanoparticle.

When speaking of spin in optics, one can think of the spinning wheel of a watermill as an illustration of the rotating ‘motion’ of the electric field vector representing the light field. Assuming the ‘water wheel’ analogy, the team’s discovery is equivalent to demonstrating that a flow of water in the canal will cause the ‘water wheel’ to spin, thus acting as a ‘water mill'. The team showed that the direction of propagation of the original wave determined the spinning sense of the electrons. This is only possible thanks to a very specific property of light waves guided along a surface which does not generally exist in free space, paving the way to a new understanding and new applications of spin on these guided light waves.

Dr Francisco Rodríguez-Fortuño, from the Department of Physics and one of the study's authors, said: ‘It has been very encouraging for us to experimentally confirm that this optical ‘watermill’ was working just as we expected. This reinforces our determination to search for new insights and novel applications of spin in guided light.’

In the experiment, the team first generated a light wave propagating along the surface of a thin gold film. This wave, called a surface plasmon, was then directed at a gold nanoparticle placed on the same surface. The interaction between them resulted in a fast spinning motion of the electrons inside the nanoparticle, in synchrony with the light’s frequency. The radiation from the circular motion of the electrons in the particle was subsequently detected, and its polarization analysed, confirming experimentally the reversibility of spin conservation.

By selecting the direction of propagation of the surface wave in such a miniaturized setup, the researchers have at their disposal a flexible and integrated way to control light spin, opening new avenues for all kinds of spinoptical devices. Last year, in a paper published in Science, they demonstrated that the direction of spinning electrons inside a nanoparticle determine the propagation direction of light along a nearby surface.

Notes to editors

Dr Rodríguez-Fortuño is available for media interview. Please contact Anna Mitchell, PR Manager, Arts & Sciences, on 0207 848 3092 or

For further information about King's visit our 'King's in Brief' page.

News Highlights:

News Highlights...RSS FeedAtom Feed

Negotiation with all extremist groups is inevitable, says Blair's ex-chief of staff

Negotiation with all extremist groups is inevitable, says Blair's ex-chief of staff

Negotiations with violent extremist groups such as Islamic State are 'inevitable', Tony Blair's former Chief of Staff Jonathan Powell said at an event at King's College London last night.Speaking at the launch of his new book: 'Talking to Terrorists', Mr Powell, who was chief negotiator in the Northern Ireland peace deal, said history has repeatedly shown that however brutal the terror tactics, face to face talks will eventually take place.
'Raising finance: Top tips from industry experts'

'Raising finance: Top tips from industry experts'

The keynote speakers, Jon Moulton, Founder and Managing Partner of Better Capital, Carlos Eduardo, Partner of Seedcamp, Julia Meyer MBE, Founder of Ariadne Capital and Nigel Verdon, Chairman and Founder of Currency Cloud, discussed their business ventures in the world of finance, offering advice and guidance to an audience of keen entrepreneurs at New Hunt's House.
Award-winning 'Strategy' an 'intellectual tour de force'

Award-winning 'Strategy' an 'intellectual tour de force'

Strategy: A History, Professor Sir Lawrence Freedman's magnum opus on the role of strategy throughout world civilization, was this week awarded the 2014 W.J.M. Mackenzie Book Prize at the Political Studies Association's annual awards in London.
Sitemap Site help Terms and conditions  Privacy policy  Accessibility  Modern slavery statement  Contact us

© 2019 King's College London | Strand | London WC2R 2LS | England | United Kingdom | Tel +44 (0)20 7836 5454