Australian scientists are controlling light at a tiny scale to unlock future technologies.
Physicists at the Australian National University, working with colleagues from China, Germany and Singapore, are using nanoparticles so small that about 12,000 can fit within a cross-section of a human hair.
These tiny particles can be arranged into unique patterns on translucent slides by manipulating light.
"The particles control the flow of light like road signs control traffic on a busy road by manipulating the direction in which light can, or can't, travel," project leader Sergey Kruk said.
The nano-technology could pave the way for a more reliable, faster and cheaper Internet. It could also serve as the foundation for many of the technologies of tomorrow, scientists say.
The tiny slides of "artificially engineered optical interactions" can show different images by manipulating the direction in which light travels through them.
As light passes through one slide, a contour map of Australia can be seen, but flip the slide and look again and a stylistic image of the Sydney Opera House is visible.
Another experimental set of images creates a chessboard pattern to confirm how the technology could work.
"While the purpose of these images is mainly artistic, they demonstrate the potential for this new technology," Lei Wang, from Southeast University in China, said.
"In real-world applications these nanoparticles can be assembled into complex systems ... such as in next-generation communications infrastructure."
Dr Kruk at ANU's Nonlinear Physics Centre said the ability to control the flow of light at the nanoscale ensures it goes where it's supposed to go.
"We exchange enormous amounts of information with the help of light," he said.
"When you make a video call, say, from Australia to Europe, your voice and image get converted into short pulses of light that travel thousands of kilometres through an optical fibre over the continents and oceans."
But light might get scattered or reflected, which compromises communication.
"By ensuring light flows exactly where it needs to flow, we would resolve many issues with current technologies," Dr Kruk said.
Their technical research has been published in Nature Photonics.