German researchers work on high-res displays | Science| In-depth reporting on science and technology | DW | 04.12.2013
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German researchers work on high-res displays

German researchers have developed a laser system for production of high-resolution displays, like in smart phones. Demand for the tech is expected to grow.

A loud buzzing: that's the sound of innovation. As Kai Schmidt stands in a windowless room, covered from head to toe in white overalls and wearing an orange protective mask over his eyes and face, he warns of the volume of the noise: "If we were to leave the protective cover off the laser, we wouldn't even be able to stand next to it. It would be much louder than we could take."

Schmidt, the head of development at Coherent - a laser company based in the central German city of Göttingen - seems small next to the five-ton laser system called the Vyper. Inside the massive steel-covered hulk of a machine are two high-powered laser tubes. The noise in the room comes from the gas discharged by the electrical energy created in the laser pipes.

The massive Vyper laser (Photo: Coherent)

The Vyper laser system is enclosed in a massive box

"Imagine you were to light up a gas discharge in the air: there would be an explosion," Schmidt said. Doing this 500 times per second makes the astonishing racket in the room.

The Göttingen researchers have managed to combine the energy from the dual laser system into a single, focused beam in a newly developed system of optics. It generates a 75-centimeter-long line of light capable of cutting pieces of glass the size of a double bed - for use in the production high-definition smart phone and tablet displays.

Use in touch screens

Plate of glass coated with polycrystalline silicon (Photo: Ansgar Pudenz/Deutscher Zukunftspreis)

Glass displays with polycrystalline silicon allow for sharper images

The sheets of glass are coated in a layer of amorphous silicon, which UV light makes melt into polycrystalline silicon, explained Ralph Delmdahl, Coherent's production marketing manager.

Delmdahl taps a finger on the screen of his iPhone, which uses polycrystalline silicon, the basis of a high-definition display. Behind each pixel is a mini-transistor - like a tiny switch - that lights up an individual pixel. The higher the definition, the more pixels and mini-transistors are jammed under the display's surface.

Polycrystalline silicon transistors are well-suited for high-definition displays because they can be made considerably smaller than amorphous silicon transistors, and the polycrystalline version also lets electrons pass through faster than amorphous silicon.

High-res for all

Laser tube (Photo: Ansgar Pudenz/Deutscher Zukunftspreis)

The laser systems have to be completely free of dust

A few doors down the hall, other employees blow compressed air on the laser pipes in a spotless room. This is where the laser's individual pieces are put together - to the highest of standards. The company's customers, which are mainly Asian display manufacturers, won't tolerate even a single speck of dust making its way into the production process.

Coherent has sold nearly 100 laser systems, and says that the market for smart phone displays is just the beginning of what it hopes will be many uses for the Vyper system.

Delmdahl explained that a digital display's power is connected with its speed. "Faster displays are good for young people, who use them for gaming, and they're good for older people too, because they can read off the displays better since the text is clearer," Delmdahl said. He added that everyone will see a benefit as high-resolution displays become an ever larger part of our lives.

Aiming bigger

Coherent's Schmidt, Pätzel and Delmdahl (Photo: Ansgar Pudenz, Deutscher Zukunftspreis)

Schmidt, Pätzel and Delmdahl are aiming to win the German Future Prize

In fact, Coherent marketing boss Rainer Pätzel said they're already looking to develop screens made from organic light diodes - or OLEDS.

You need to have polycrystalline silicon displays in order to make OLED televisions. "That's the stage we've reached," he said. There are still challenges, he added, for example automation and more stable operation. "Those are the things we're still researching and developing," Pätzel said.

The lasers can already process sheets of glass of up to five square meters in size. But Schmidt and his colleagues are working to triple the laser's power in order to work on even larger pieces of glass. And to do it, they're more than willing to put up with the noise.

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