A new generation of TVs could be built around pixels made of metasurfaces that can switch their transparency on and off thousands of times a second.

As well as offering a fast refresh rate, the metasurfaces are 100 times thinner than liquid crystal cells, offer a tenfold greater resolution and could consume less energy, said the leader of the ANU research team, Professor Dragomir Neshev.

“Today there is a quest for fully solid-state flat display technology with a high-resolution and fast refresh rate.

“But the capability of conventional displays has reached its peak and is unlikely to significantly improve in the future due to multiple limitations,” said Professor Neshev, who is Director of the ARC Centre for Excellence in Transformative Meta-Optical Systems (TMOS) and professor in the Department of Electronic Materials Engineering.

“We have designed and developed metasurface pixels that can be ideal for the next-generation display.

“Unlike liquid crystals, our pixels do not require polarised lights for functioning, which will halve screens’ energy consumption.”

The global market value for flat screens was about $117 billion in 2020, much of that based on liquid crystal displays (LCDs).

Metasurfaces outperform LCDs thanks to the light control that is possible with careful engineering of the surface pattern. Their surprising qualities are generated by an array of regular structures that are smaller than the wavelength of the light that is being controlled, said Khosro Zangeneh Kamali, a PhD scholar at ANU and the first author of the study, in Light: Science & Application.

“Metasurfaces are proven to exhibit extraordinary optical behaviour. 

“However, inventing an effective way to control them is still a subject of heavy research. We have proposed a versatile platform - electrically programmable silicon metasurfaces,” Mr Zangeneh Kamali said.

The research team were able to program their pixel’s transparency with heat, which was delivered via an electric current, provided by a transparent conducting layer built into the silicon metasurface.

The heat changed the refractive index of the metasurface enough to change the transmission of a red laser through the pixel by a factor of nine, in less than a millisecond.

Each pixel was as small as 100 x 100 micrometers square (less than half standard current pixel size), and a mere 150nm thick (100th the thickness of a hair).

Another advantage of the new pixel is it is compatible with existing silicon-based technology, said Professor Andrey Miroshnichenko, a team member from the University of New South Wales Canberra.

“Our pixels are made of silicon, which offers a long lifespan, in contrast with organic materials required for other existing alternatives.

“Moreover, silicon is widely available, CMOS compatible with mature technology, and cheap to produce.”

Lead researcher Mohsen Rahmani, Professor of Engineering at Nottingham Trent University said the breakthrough could supersede existing screen technology.

“We have paved the way to break a technology barrier by replacing the liquid crystal layer in current displays with a metasurface, enabling us to make affordable flat screens liquid crystal-free.

“The most important metrics of flat panel displays are pixel size and resolution, weight and power consumption. We have addressed each of these with our meta-display concept.

“Most importantly, our new technology can lead to a huge reduction of energy consumption – this is excellent news given the number of monitors and TV sets being used in households and businesses every single day. We believe it is time for LCD and LED displays to be phased out in the same way as former cathode ray tube (CRT) TVs over the past ten to 20 years,” Professor Rahmani said.

Dr Lei Xu, a team member from Nottingham Trent University, said: “There is significant room for further improvements by employing artificial intelligence and machine learning techniques to design and realise even smaller, thinner and more efficient metasurface displays.”