From the Princeton Weekly Bulletin October 6, 1997
POEM group develops organic laser
By Steve Eisenberg
Researchers have produced a laser using organic material that may have widespread industrial and consumer applications. The material -- a composite of carbon, hydrogen, oxygen and nitrogen -- is less expensive to manufacture and less temperature-sensitive than the semiconductor material in today's lasers, such as those in compact disc players.
Previously, researchers in the laser community thought organic materials were not suitable for making lasers. The prevailing belief was that the material was not strong enough to withstand extended exposure to the high optical powers or electrical currents necessary for sustained losing to occur. (Lasers generate coherent, focused electromagnetic radiation that is often visible as light; they use the natural oscillations of atoms or molecules as they become excited by the injection of energy.)
In the September 25 issue of Nature, Stephen Forrest, McDonnell Distinguished University Professor of Electrical Engineering, and his research group at the Center for Photonics and Optoelectronic Materials (POEM) describe how they produced a light source of roughly 50 watts peak power from an organic material one-thousandth the width of a human hair. Hypothetically, if the same organic material replaced the filament in a 50-watt light bulb, 10 thousand watts would be produced.
"It's pretty exciting to get so much light coming out of these organic lasers," says Forrest, who collaborated with postdoctoral fellow Vladimir Kozlov, graduate student Vladimir Bulovic and research scholar Paul Burrows on the year-long research project.
Stimulated by nitrogen laser
Unlike conventional lasers, which produce beams of highly focused light after electrical current pulses the laser material, the current version of the organic laser creates its energy in a less direct method. Using a nitrogen laser in the lab, Forrest and his colleagues shine ultraviolet light on the organic composite--a mixture of "host" material (tris-8-hydroxyquinoline aluminum), and the laser-producing material (DCM laser dye), which comprises only one percent of the total package. The host absorbs the ultra-violet light and transfers the energy to the DCM laser dye, which produces the laser light.
Although both materials are commercially available, the secret to the current success was discovering the right composition for the laser material and the correct structure that would emit laser light. One of the research project's next steps is developing an organic laser that can be electrically stimulated, as opposed to being stimulated by another light source.
Because organic materials are less expensive than the most commonly used semiconductors in today's lasers, such as gallium arsenide, it may be possible to either lower production costs or increase the number of lasers in several industrial and consumer applications, which would improve performance. For instance, in compact disc players, CD-ROM players or optical memory devices, it may be possible to have several hundred lasers as opposed to one for the same price. More lasers used throughout the machine would allow for more rapid access of stored information.
Extends previous research
The new laser extends research by Forrest and others into the development of light-emitting devices, comprising very thin films of organic materials. In June, Forrest and other researchers at Princeton and the University of Southern California announced the creation of an independently controlled, three-color organic light-emitting device, which is expected to lead to such applications as high-definition televisions with flat displays and laptop computers with bright displays that consume considerably less energy.
Funding for the organic laser research came from Universal Display Corp. (UDC), National Science Foundation and U.S. Air Force Office of Scientific Research. Applications of the research into organic light-emitting devices have been licensed exclusively to UDC. POEM is sponsored in part by the N.J. Commission on Science and Technology.
1006-poem.html