First electrically pumped organic laser

17 Jun 2002

Physicists at Bell Labs, the research and development arm of Lucent Technologies, have developed what they claim is the first electrically powered organic laser, a breakthrough that may lead to more widespread use of lasers in various applications. The organic laser could be less expensive to manufacture than today's conventional inorganic semiconductor lasers.

Previous organic lasers had been powered by light sources, such as other lasers, which can limit their applications. Electrically powered lasers are preferred because they are compact and can be integrated with complex electronic circuitry.

Because organic materials are less expensive than the inorganic semiconductor materials used in today's lasers, such as gallium arsenide, it may be possible to decrease production costs of individual lasers. Alternatively, it may be possible to have several hundred lasers -- as opposed to one -- for the same price in a machine, such as an optical storage device or laser printer, which would allow for more rapid access or display of stored information.

To make the organic laser, Bell Labs scientist Christian Kloc first grew high-quality crystals of tetracene, which is an organic molecule with four connected benzene rings that conducts electricity well. When the researchers injected electric current to "excite" the tetracene to emit light, the light bounced back and forth between mirrors in the material, eventually producing beams of intense yellow-green light.

"Previously, researchers in the laser community thought organic materials would never be able to carry the large current necessary for electrically powered organic lasers," said Bertram Batlogg, head of Bell Labs' solid state physics research department, who collaborated with Kloc, Hendrik Schon and Ananth Dodabalapur on the research.

Tetracene, however, is among the purest organic semiconductors, which leads to the desired electrical properties needed for a laser. "The tetracene crystal remains transparent just before the intense beams of light are formed," Batlogg said, "which means very little light is absorbed, thereby enhancing the lasing effect."

"These research results open up a whole new set of possibilities for electrically driven lasers," said Federico Capasso, physical research vice president at Bell Labs. "They not only would be inexpensive to manufacture, but they could be tailor made to produce a wide range of wavelengths, each of which could have specific applications. They can be driven by today's silicon circuitry and may someday be combined with plastic transistors, which would further reduce production costs and potentially lead to lightweight, flexible products."

Because the current configuration of the Bell Labs organic laser operates at a visible wavelength, it is not yet appropriate for optical communications.