Scientists squeeze more out of light

By John Nixon 10/12/2009

Scientists at the University of Adelaide, Australia, have put the squeeze on light. By discovering that light within optical fibers can be squeezed into much tighter spaces than was previously believed possible, the researchers at the University’s Institute for Photonics and Advanced Sensing (IPAS) have claimed a breakthrough that could change the world’s thinking on light’s capabilities, especially when it comes to its use in telecommunications, such as fiber-to-the-home (FTTH), computing and other light sources.

To get light to travel along an optical fiber, it must concentrated, aimed and bounced along the inside walls of the fiber which acts like a pipe for light. But as the size of the fiber shrinks (in our never-ending quest for smaller, faster, better), the light becomes more and more confined too, until it reaches the ultimate limit — the point beyond which it cannot be squeezed any smaller.

This ultimate point occurs when the strand of glass (fiber) is just a few hundred nanometers in diameter, about one thousandth of the size of a human hair. If you go smaller than this, light begins to spread out again.

The Adelaide researchers say they have discovered a way in which they can push beyond that limit by at least a factor of two. They can do this due to new breakthroughs in the theoretical understanding of how light behaves at the nanoscale, and by using a new generation of nanoscale optical fibers being developed at the institute.

This discovery by IPAS Reserach Fellow Dr Shahraam Afshar is expected to lead to more efficient tools for optical data processing in telecommunications networks and optical computing, as well as new light sources. Federation Fellow at the University of Adelaide and Director of IPAS, Prof Tanya Monro, says Dr Afshar’s discovery is “a fundamental breakthrough in the science of light”.

“By being able to use our optical fibers as sensors — rather than just using them as pipes to transmit light — we can develop tools that, for example, could easily detect the presence of a flu virus at an airport; could help IVF (in vitro fertilization) specialists to determine which egg should be chosen for fertilization; could gauge the safety of drinking water; or could alert maintenance crews to corrosion occurring in the structure of an aircraft,” says Professor Monro.

Another IPAS researcher, Dr Yinlan Ruan, also recently created what is thought to be the world’s smallest hole inside an optical fiber — just 25 nanometers in diameter.

“These breakthroughs feed directly into our applied work to develop nanoscale sensors,” Prof Monro says. “They will enable us to study the applications of light at much smaller scales than we’ve ever thought possible. It will help us to better understand and probe our world in ever smaller dimensions.”