They can weld, cut or drill anything. They transmit phone calls in optical fibers, act as chemical sensors, produce computer printouts and create holograms to prevent credit-card forgery. Surgeons use them to correct vision, close wounds and remove tumors, clots and birthmarks. Lasers aim missiles and guns, etch circuits, detect speeding motorists, scan grocery prices and read information on compact discs.
The beams of intense light in many conventional lasers are produced by
atoms in a gas or in liquids. But for lasers to be small enough to work
in miniature electronic
devices, the beams are generated by solids (such as semiconductors),
since their molecules are more compact than those in gases and liquids.Now, physicists worldwide are racing to develop a new generation of solid-state lasers produced by plastics instead of silicon semiconductors, said Valy Vardeny, physics chairman at the University of Utah.
Vardeny said lightweight "plastic lasers" would be cheaper, easier and safer to make than semiconductor lasers. They could produce all the colors of the rainbow and would be shaped easily into films, rings, microscopic discs or any desired shape for various uses, such as display devices and computer circuits that run at the speed of light instead of the slower speed of electricity.
Before plastic lasers are practical, numerous technical problems must be overcome, including how to use electricity to stimulate the plastic to emit a laser beam.
In the Feb. 4 issue of the journal Science, Vardeny reported progress toward solving that problem. He and his colleagues identified a kind of plastic that is more receptive to electrical stimulation than other plastics tried so far.
Vardeny conducted the study with former U. exchange student Ron Osterbacka, now on the faculty at Finland's Abo Akademi University; Chong An, a postdoctoral physicist at the U.; and physics graduate student Xiaomei Jiang.
The study "is only a small step toward achievement of a plastic laser, but it's an important step that indicates the possibility of making plastic lasers work with electricity," Vardeny said.
Vardeny's study represents "good progress, nice results," said Alan Heeger, a professor of physics and materials at the University of California, Santa Barbara.
Laser is an acronym for "light amplification by stimulated emission of radiation." Lasers are intense because they emit a single color of light that is "coherent," meaning all the light waves have the same width and height. To produce a laser beam, atoms of gas, liquid or solid must be stimulated or excited from a low-energy to a high-energy state. They also must be contained in a "cavity" -- usually a chamber with mirrors that focus the laser light into a beam.
One advantage of plastic lasers is that the plastics act as their own cavities, not only emitting laser light but containing and focusing it.
Vardeny said lasers made of plastic also are flexible, so they can be made into films or "microdiscs." Vardeny has made such microdiscs, which are so small that 6,350 of them in a line would be an inch long. He said that when such discs can be powered by electricity to emit laser light, they could be used for display devices -- such as televisions, automobile dashboards and wrist watches -- or lined up in a computer chip to switch and transmit signals at the speed of light.
Plastic laser material also can be dissolved in
solvents and applied as a coating. A plastic laser film wrapped around
an optical fiber could amplify light moving through
the fiber. Or, if wrapped around a wire, the wire could stimulate the
laser coating to emit light, perhaps in a computer circuit, Vardeny
said.Almost all existing solid-state lasers can emit only red and infrared light, Vardeny said. Plastic lasers could emit colors such as green and blue, which have shorter wavelengths. A laser with a shorter wavelength is like having a finer paint brush, so blue and green plastic lasers could write more information on storage discs than redlasers, Vardeny said.
When Theodore Maiman built the first working laser in 1960, no one had any idea how useful they would be. The same is likely true for plastic lasers.
"There are lots of possibilities we will all be inventing if and when the problems to make the plastic laser are solved," Heeger said. Because they should be able to emit all colors, plastic lasers likely will be used in display devices and "all the things we use colored light for," he said.
Just as optical fibers can carry much more information than electrical wires, Vardeny's work is aimed at developing computer chips and other devices that would work at higher speeds because they "operate based on light rather than electrons," said Ray Baughman, a materials scientist at Honeywell International in Morristown, N.J.
Baughman said Vardeny's research "provides fundamental insight into processes that can result either in the emission of light or in the conversion of light into electrical current. He's a world-class pioneer."
Originally published February 10, 2000, in The Salt Lake Tribune.