Nanoparticles that control the flow of light could mean a faster, cheaper internet

Imagine a window with a picture engraved on its surface, but when you walk around the other side, the picture is completely different.

Although that sounds impossible, essentially this is what researchers from the Australian National University (ANU) have achieved, with tiny translucent slides that can display two different images, at the same time, when viewed from opposite sides.

In one experiment, for example, 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 optical computing – using visible or infrared light instead of an electric current to perform numerical calculations.

The researchers said these new light-based devices could eventually lead to faster and cheaper internet.

It was their search Published in Nature Photonics today.

How it works?

As you may have noticed, light usually travels along the same path back and forth through a material such as glass or water.

To change this, the researchers created tiny glass slides covered in cylindrical nanoparticles, each particle so small that 12,000 of them could fit within the cross-section of a human hair.

Supplied: ANU
ANU physicist Serge Kroc hopes to see applications in computing.(Supplied: ANU)

Each cylinder controls the flow of light like road signs direct traffic, said Sergey Kroc, a physicist at ANU and co-author of the paper.

“We were able to introduce an asymmetry in the way the light propagates,” he said.

“So when the light is scattered forward and when it is scattered backward, we get completely different results.”

The technical name for these “guideboards” is “non-linear dielectric resonators”.

The cylinders were made of two layers of silicon and silicon nitride. Each layer has a different refractive index – a measure of how fast light travels through a medium, and thus the material’s ability to bend light.

The different refractive indices of air and water, for example, are why a spoon in a glass of water appears to be bent.

These cylinders can be positioned to be ‘bright’ or ‘dark’ for the back or forward directions only, or ‘bright’ or ‘dark’ for both the front and rear directions.

Asymmetric parametric generation of images
The nanoparticles were arranged to form images ⁠— in this case, the Sydney Opera House and a map of Australia.(Supplied: Sergey Kroc et al)

By arranging these four types of cylinders in patterns, Dr. Kroc and colleagues from China, Germany and Singapore were able to create the images.

“Slices are basically made up of individual pixels,” Dr. Kroc said.

“And we can group these pixels into any patterns you want. “

light computing

Benjamin Eagleton, director of the Sydney Nano Institute, called the research “significant” and a “fundamental finding”.

“It’s an intrinsic heroic advance,” said Professor Eagleton, who was not involved in the research.

The most obvious application, he said, is “nanophotonic components” for computing.

a A key component of electronic computing and the complex architecture of microchips is a diode that allows electric current to flow in only one direction.

Photographs (top and bottom right) of opposite sides of a nano-engineered chip
Photographs (top and bottom right) of opposite sides of a nano-engineered slice.(Supplied: Sergey Kroc et al)

In photonics, or light-based computing, a diode is called an isolator.

current yield of Prof. Eagleton said insulators are relatively bulky and complex, but ANU’s research could lead to much smaller and simpler designs.

Optical circuits, or optical computing, have been called the future of computing, as they can be made smaller than electronic circuits, operate at higher speeds, use less energy, and generate less heat.

“Many of the leading companies in the commercialization of quantum computer technology rely on optical circuits,” Professor Eagleton said.

“And in those circuits, you’re going to need these insulators.”

faster internet?

Dr. Kroc also saw applications in optical circuits.

This could eventually lead to faster and cheaper internet, he said.

Two years ago, for example, researchers built a photonic circuit that works on a clock 44.2 Tbps Across 76 kilometers of optical fiber installed between two campuses in Melbourne.