Study Shows How Nanoparticles May Control the Flow of Light Like Road Signs

Scientists from the Australian National University (ANU) have invented small transparent slides that can produce two quite distinct pictures depending on the way light flows through them.

Study Shows How Nanoparticles May Control the Flow of Light Like Road Signs.
An illustration of the ANU tiny slides. Image Credit: Ella Maru Studio.

A picture of Australia appears as the light goes through the slide, but when users flip it over and look again, users see a picture of the Sydney Opera House. The graphics are only one sample of the vast array of options available.

The ANU scientists’ ability to regulate the direction in which light can and cannot flow at the nanoscale allows them to create two separate pictures. The breakthrough might open the door for new light-based gadgets, resulting in a quicker, more affordable, and more dependable Internet. It may also serve as the cornerstone for many of tomorrow’s innovations.

The new technique, which was developed in partnership with colleagues from China, Germany, and Singapore, employs nanoparticles that are so tiny that 12,000 of them can fit into a cross-section of human hair. On the slides, these small particles are organized in distinctive patterns.

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. Some particles allow light to flow from left to right only, others from right to left or the pathway might be blocked in either direction.

Dr. Sergey Kruk, Project Leader, Nonlinear Physics Center, Research School of Physics, Australian National University

Dr. Lei Wang, from Southeast University in China, added, “While the purpose of these images is mainly artistic, they demonstrate the potential for this new technology. In real-world applications these nanoparticles can be assembled into complex systems that would control the flow of light in a useful manner - such as in next-generation communications infrastructure.”

The capacity to control the flow of light at the nanoscale, according to Dr. Kruk, makes sure that light “goes where it’s supposed to go and doesn’t go where it’s not supposed to

We exchange enormous amounts of information with the help of light. 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 kilometers through an optical fiber over the continents and oceans.

Dr. Sergey Kruk, Project Leader, Nonlinear Physics Center, Research School of Physics, Australian National University

Unfortunately, when we use current light-based technologies to exchange information a lot of parasitic effects might occur. Light might get scattered or reflected, which compromises your communication. By ensuring light flows exactly where it needs to flow, we would resolve many issues with current technologies,” stated Dr. Kruk.

While optical isolators, which can restrict the flow of light, are currently on the market, this technology has certain limitations.

Optical isolators are indispensable in many high-end light-based technologies such as powerful lasers and ultra-fast optical communication networks, but they are quite large in size and are also expensive, which prohibits a wider deployment of these components.

Dr. Sergey Kruk, Project Leader, Nonlinear Physics Center, Research School of Physics, Australian National University

Dr. Kruk also noted, “By contrast, our devices are created using nanofabrication technology. This allows us to drastically reduce the size of a component to less than one thousandth of a millimeter and reduce production costs to just a fraction of an Australian dollar.”

Currently there is one important difference between an optical isolator and the first generation of our translucent slides. Our slides change the color of light, or in other words, the frequency at which the wave of light oscillates, while an optical isolator does not. We are now working on the second generation of this technology that will control the flow of light in the same way, while maintaining its color,” explained Dr. Kruk.

Many of tomorrow’s technologies, according to Dr. Kruk, will rely significantly on the capacity to regulate light on a microscale.

A wide deployment of tiny components that can control the flow of light could potentially bring technological and social changes similar to transformations brought about in the past by the development of tiny components that control the flow of electricity, which are known as diodes and transistors,” said Dr Kruk.

Control over the flow of electricity at the nanoscale is what ultimately brought us modern computers and smartphones. It is therefore exciting to envision the potential of our emerging technology for controlling flow of light,” Dr. Kruk concluded.

The Nonlinear Physics Centre at ANU Research School of Physics, Paderborn University in Germany, Southeast University in China, and A*STAR Singapore collaborated on this study.

Journal Reference:

Kruk, S. S., et al. (2022) Asymmetric parametric generation of images with nonlinear dielectric metasurfaces. Nature Photonics.


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