As that information travels at the speed of light across the globe, the energy of the light waves bouncing around inside the silica and polymer fibres create tiny vibrations that lead to feedback packets of sound or acoustic waves, known as 'phonons'.This feedback causes light to disperse, a phenomenon known as 'Brillouin scattering'.
For most of the electronics and communications industry, this scattering of light is a nuisance, reducing the power of the signal. But for an emerging group of scientists this feedback process is being adapted to develop a new generation of integrated circuits that promise to revolutionise our 5G and broadband networks, sensors, satellite communication, radar systems, defence systems and even radio astronomy.sound chip recordable
"It's no exaggeration to say there is a research renaissance into this process under way," said Professor Ben Eggleton, Director of the University of Sydney Nano Institute and co-author of a review paper published today in Nature Photonics."The application of this interaction between light and sound on a chip offers the opportunity for a third-wave revolution in integrated circuits."
The microelectronics discoveries after World War II represented the first wave in integrated circuitry, which led to the ubiquity of electronic devices that rely on silicon chips, such as the mobile phone. The second wave came at the turn of this century with the development of optical electronics systems that have become the backbone of huge data centres around the world.
First electricity then light. And now the third wave is with sound waves.Professor Eggleton is a world-leading researcher investigating how to apply this photon-phonon interaction to solve real-world problems. His research team based at the Sydney Nanoscience Hub and the School of Physics has produced more than 70 papers on the topic.
Working with other global leaders in the field, today he has published a review article in Nature Photonics outlining the history and potential of what scientists refer to as 'Brillouin integrated photonics'. His co-authors are Professor Christopher Poulton at the University of Technology Sydney; Professor Peter Rakich from Yale University; Professor Michael Steel at Macquarie University; and Professor Gaurav Bahl from the University of Illinois at Urbana-Champaign.
Professor Bahl said: "This paper outlines the rich physics that emerges from such a fundamental interaction as that between light and sound, which is found in all states of matter.
"Not only do we see immense technological applications, but also the wealth of pure scientific investigations that are made possible. Brillouin scattering of light helps us measure material properties, transform how light and sound move through materials, cool down small objects, measure space, time and inertia, and even transport optical information."Professor Poulton said: "The big advance here is in the simultaneous control of light and sound waves on really small scales.
"This type of control is incredibly difficult, not least because the two types of waves have extremely different speeds. The enormous advances in fabrication and theory outlined in this paper demonstrate that this problem can be solved, and that powerful interactions between light and sound such as Brillouin scattering can now be harnessed on a single chip. This opens the door to a whole host of applications that connect optics and electronics."
Professor Steel said: "One of the fascinating aspects of integrated Brillouin technology is that it spans the range from fundamental discoveries in sound-light interactions at the quantum level to very practical devices, such as flexible filters in mobile communications."The scattering of light caused by its interaction with acoustic phonons was predicted by French physicist Leon Brillouin in 1922.
