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Rajesh Menon holds up the prototype of the first flat thin camera lens developed by his team

Glass revolutionising graphene displays and cameras

Three teams of scientists are using glass in research projects that could bring graphene into the mainstream, allow windows to function as screens and produce ultra-slimline smartphone cameras.

Scientists at the US Department of Energy's Brookhaven National Laboratory have developed a simple and powerful method for creating resilient, customised and high-performing graphene by layering it on top of common glass.

The new process, which is inexpensive and can be scaled up to commercial levels, has the potential to develop a new class of microelectronic and optoelectronic devices, including super-efficient solar cells and touch screens.

"We believe that this work could significantly advance the development of truly scalable graphene technologies," said Matthew Eisaman with Brookhaven Lab.

The team has constructed a proof-of-concept graphene device using soda-lime glass, which is typically used in windows and bottles, to boost the electronic properties of graphene.

"The sodium inside the soda-lime glass creates high electron density in the graphene, which is essential to many processes and has been challenging to achieve," said Nanditha Dissanayake, a co-author on the project.

The electronic effect remained strong even when the devices were exposed to air for several weeks - a significant improvement over techniques designed to harness graphene’s electrical properties.

Eisaman said that the potential applications for graphene are numerous and could boost everything from gadgets to energy harvesting technologies.

"It's too early to tell exactly what impact our results will have, but this is an important step toward possibly making some of these applications truly affordable and scalable," he said.

A separate team at the University of British Columbia (UBC) has also been experimenting with glass coatings which could allow traditional windows to double as a giant TV screen. They found that coating small pieces of glass with extremely thin layers of metal makes it possible to enhance the amount of light coming through the glass.

By using conducting metals such as silver, it is possible to add advanced technologies to windowpanes and other glass objects.

"Engineers are constantly trying to expand the scope of materials that they can use for display technologies and having thin, inexpensive, see-through components that conduct electricity will be huge," said UBC Professor Kenneth Chau. "I think one of the most important implications of this research is the potential to integrate electronic capabilities into windows and make them smart."

The team also plans to incorporate their invention into windows in order to selectively filter light and heat waves depending on the season or time of day.

"It's been known for quite a while that you could put glass on metal to make metal more transparent, but people have never put metal on top of glass to make glass more transparent," said Markley.

"It's counter-intuitive to think that metal could be used to enhance light transmission, but we saw that this was actually possible and our experiments are the first to prove it."

Lastly, University of Utah researchers have found a way to drastically reduce the thickness of camera lenses which could allow for slimline smartphone’s that have the photographic capabilities of DSLR’s.

Traditional camera lenses are relatively bulky due to the need for multiple glass layers that are optimised for different colours in the light spectrum.

The team, led by University professor Rajesh Menon, has developed a new method of creating optics that are flat and thin, yet can still perform the function of bending light to a single point, the basic step in producing an image.

"Instead of the lens having a curvature, it can be very flat so you get completely new design opportunities for imaging systems like the ones in your mobile phone," Menon said. "Our results correct a widespread misconception that flat, diffractive lenses cannot be corrected for all colours simultaneously."

The experimental lenses can be constructed 10 times thinner than the width of a human, which is millions of times thinner than a camera lens today. It is done through a principle known as diffraction in which light interacts with microstructures in the lens and bends.

"In nature, we see this when you look at certain butterfly wings. The color of the wings is from diffraction. If you look at a rainbow, it's from diffraction," said Menon. "What's new is we showed that we could actually engineer the bending of light through diffraction in such a way that the different colours all come to focus at the same point. That is what people believed could not be done."

The new lenses use specially created algorithms to calculate their geometry so that the full range of colours can pass through it and focus to a single point. The resulting lens, called a ‘super-achromatic lens’, can be made of any transparent material such as glass or plastic.

The technology could be used for a wide array of applications such as tiny medical devices that can peer into the human body, adding much lighter cameras to drones and satellites to reduce weight and imbuing future smartphones with high-powered cameras that don't require the lens jetting out from the phone's thin body.

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