Imagine a window with a picture on the surface, but when you walk to the other side, the picture is very different.
Most important points:
- Nanoengineering manipulates the path light travels through a material
- This allows two different images to be seen when viewed from opposite sides
- “Nonlinear Optics” Could Have Applications in Computing and Lead to Faster Internet
While it may sound impossible, that’s essentially what researchers at the Australian National University (ANU) have achieved, with small translucent slides that can show two different images at the same time, when viewed from opposite sides.
For example, in one experiment, the scientists created a slide showing the continent of Australia on one side and the Sydney Opera House on the other.
Advances in the field known as “nonlinear optics” could have applications in photonic computing — the use of visible light or infrared instead of electrical current to perform digital calculations.
These new light-based devices could eventually lead to faster and cheaper internet, the researchers said.
Their research was: published today in Nature Photonics†
How does it work?
As you may have noticed, light usually travels forward and backward along the same path through a material such as glass or water.
To change this, the researchers created tiny glass slides covered with cylindrical nanoparticles, each particle so small that 12,000 of them would fit into the cross-section of a human hair.
Each cylinder controlled the flow of light like road signs directing traffic, said Sergey Kruk, an ANU physicist and co-author of the paper.
“We were able to introduce asymmetry in the way light propagates,” he said.
“So when light propagates forward and when it propagates backward, we get completely different results.”
The technical name for these “road signs” is “non-linear dielectric resonators”.
The cylinders were made of two layers of silicon and silicon nitride. Each layer had a different index of refraction — a measure of how fast light travels through a medium, and thus the material’s light-bending ability.
For example, the different refractive indices of air and water make a spoon in a glass of water look like it’s bent.
These cylinders can be positioned to be “bright” or “dark” for only the backward or forward directions, or “bright” or “dark” for both forward and reverse.
By arranging these four types of cylinders in patterns, Dr. Kruk and his colleagues from China, Germany and Singapore were able to form images.
“Basically, the slides are made up of individual pixels,” said Dr. Kruk.
“And we can put these pixels together in any pattern we want†
Benjamin Eggleton, director of the Sydney Nano Institute, described the research as “important” and a “fundamental result”.
“It’s a heroic fundamental advance,” said Professor Eggleton, who was not involved in the study.
The most obvious application, he said, was “nano-photonic components” for computers.
A The most important part of electronic computing and the complex architecture of microchips is the diode that allows electrical current to flow in only one direction.
In photonics, or light-based computing, a diode is called an insulator.
The current crop of insulators are relatively bulky and complicated, but the ANU research could lead to much smaller and simpler designs, Professor Eggleton said.
Photonic circuits, or optical computers, have been called the future of computers because they can be made smaller than electronic ones, run at higher speeds, consume less energy and generate less heat.
†Many of the leading companies commercializing quantum computing technology rely on photonic circuits,” said Professor Eggleton.
“And on those circuits you need these insulators.”
dr. Kruk also saw applications in photonic circuits.
This could eventually lead to faster and cheaper internet, he said.
For example, two years ago, researchers built a photonic circuit that clocked 44.2 terabits per second installed over 76 kilometers of optical fibers between two university campuses in Melbourne.
By comparison, that’s about 1 million times faster than the average broadband download speed in Australia.
Physicists are just beginning to understand how intense light interacts with the structure of nanoscale materials, said Dr. Kruk.
†At this stage of technological development, we have become incredibly good at controlling electric currents, and we are not very good at controlling light rays.
†This one [research] may be a first convincing step towards a very advanced traffic control of light beams.
†[This is] comparable to highly sophisticated traffic control of electric currents, which we may have started to establish in the mid-20th century.”