Scientists at the University of California have developed a way to squeeze light into tighter spaces, potentially opening doors to new technology in the fields of optical communications, miniature lasers and optical computers.

Previously optics researchers had managed to pass light through gaps 200 nanometers wide – about 400 times smaller than the width of a human hair. A group of UC Berkeley researchers led by mechanical engineering professor Xiang Zhang, devised a way to confine light in spaces measuring 10 nanometers, just five times the width of a single piece of DNA and more than 100 times thinner than current optical fibres.

Rupert Oulton, research associate, and lead author of the study explained: “This technique could give us remarkable control over light, and that would spell out amazing things for the future in terms of what we could do with that light.”

Not only would compressed light make possible smaller optical fibres, but it could lead to advances in the field of optical computing. Many researchers want to link electronics and optics, but the vast difference between the characteristic sizes of the two makes this difficult. However, confining light can actually alter the fundamental interaction between light and matter. Ideally, optics researchers would like to cram light down to the size of electron wavelengths to force light and matter to co-operate.

Compressing light further than its wavelength created a problem for the researchers, as light doesn’t want to stay inside a space that small. As researchers have squashed light beyond these limits using surface plasmonics, where light binds to electrons allowing it to propagate along the surface metal. But the waves only travel a short distance before petering out.

In order to mitigate the losses, Oulton came up with the idea from a ‘hybrid’ optical fibre, consisting of a very thin semiconductor wire placed close to a smooth sheet of silver.

Oulton ran computer simulations to test this idea. He found that not only could the light compress into spaces only tens of nanometers wide, but it could travel distances nearly 100 times greater in simulation than by conventional surface plasmonics alone. Instead of the light moving down the centre of the thin wire, as the wire approaches the metal sheet, light waves trapped in the gap between them, the researchers found.

The research team’s technique works because the hybrid system acts like a capacitor, Oulton said, storing energy between the wire and the metal sheet. As the light travels along the gap, it simulates the build-up of charges on both the wire and the metal, and these charges allow the energy to be sustained for longer distances.

Oulton believes the hybrid technique of confining light could have huge ramifications. It brings light closer to the scale of electrons’ wavelengths, meaning that new links between optical and electronic communications might be possible.”