A team of researchers led by the University of Cambridge have created the “world’s smallest magnifying glass” that confines light to volumes smaller than the size of a single atom for the very first time. The results, which were published this week in the journal Science, will help to establish greater understanding of the interactions between light and matter.

It had been the long-held belief of scientists that light could not be focused down beyond its wavelength. However, by utilising the highly conductive nature of gold nanoparticles, the researchers were able to concentrate light a billion times more tightly – down to the scale of a single atom.

Working in collaboration with partners from European universities, the research team produced the world’s tiniest optical cavities – which they labelled as ‘pico-cavities’ – that are large enough to accommodate just a single molecule. These pico-cavities are essentially bumps in the gold nanostructure that confine light down to less than a billionth of a metre and potentially enable scientists to control and watch single atoms in real time.

The lead researcher Professor Jeremy Baumberg of the NanoPhotonics Centre at the University of Cambridge’s Cavendish Laboratory reiterated the fundamental importance of the research in the field of cavity opto-mechanics, the study of how light interacts with material objects. He explained, “we now understand how it is possible to ‘see’ single atoms at a molecular scale using light which has a wavelength that is a thousand times larger”.

The pioneering research establishes the foundations for further investigations, including into the possibility of observing the mechanisms involved in the formation and breakdown of chemical bonds between atoms. The ability to control single atoms creates the possibility that chemical reactions could be manipulated and catalysed by light, potentially enabling physicists to construct complex molecular structures from single component atoms.

Felix Benz, the experimental lead author of the study, also heralded the benefits. “This marks a big step in the field of nano-spectroscopy as it demonstrates that we can actually go from merely observing the vibrations of a single molecule to actively influencing them”.

The development of ‘pico-cavities’ could open up a plethora of opportunities.  For example, from the construction of opto-mechanical data storage devices to the development of ultra-sensitive sensors – enabling information and data to be stored as molecular vibrations and written and read by light.

Professor Baumberg is also concerned with advancing the research and applying it in a practical sense: “We are interested in just how far we can go. By using the vibrating bonds in single molecules as tiny springs, which can be plucked, we could then make switches with this that work with a very small energy input – this could be significant given that all our information handling through the internet uses enormous amounts of energy across the globe. We also want to watch the proteins involved in the processes of life – how they move and how they flex to select and bind to other molecules.”