Lasers Printed on Paper with Inkjet Tech
Lasers are everywhere — in DVD players, fiber optic
communications and even displays. They are so useful it would be great if they
were flexible and easy to make, but that hasn't been the case, until now.
Researchers at the University of Cambridge in the United Kingdom have developed a way to print lasers on a variety of surfaces using
a printer similar to an inkjet version. The technique could improve display technologies and also lead to better drugs that treat disease.
The team, led by D. J. Gardiner of the Center for
Molecular Materials for Photonics, started with an inkjet-like printer and "ink" made from a solution of fluorescent dye and liquid crystals like those used in liquid crystal displays, or LCDs. After putting the liquid crystal ink into the printer, the scientists printed tiny dots onto a wet polymer that covered a substrate. The polymer
dried out and in the process caused spiral-shaped molecules in the liquid crystals to align in a particular way.
The alignment is important because the spiral acts like an optical cavity, confining the lightwaves and forcing them to move "in step," or coherently, the way laser beams move.
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Once the dots were dry, the scientists shone a different laser through the printed material. This "pumped" the liquid crystals and fluorescent dye, producing the extra energy needed to create a laser beam.
Gardiner told Discovery News that while it might seem odd to use a laser beam to create a laser beam, the method is efficient because they use a simpler laser to create smaller, more complicated lasers.
Once the laser was shone onto the printed dots, the dots emitted laser light in either one or two directions. If the material printed on was opaque, the laser light went one way, and if it was transparent, the light got emitted both front and back.
A big benefit with this method is that by changing the color of the fluorescent dye and the spiral shape of the molecules, scientists can control the wavelength of laser light. There are some wavelengths for which lasers are expensive and difficult to build. And this makes it easier and cheaper.
This kind of technology could be used for displays, but Gardiner said he
sees more immediate applications in sensing and diagnostics. Currently,
several kinds of medical tests involve attaching flourescent dyes to a
molecule of interest
and then hitting it with a laser beam. Being able to print an array of