New mechanism found for making common electronic materials emit laser beams

December 23rd, 2008 - 5:12 pm ICT by ANI  

Washington, Dec 23 (ANI): A team of researchers has discovered an entirely new mechanism for making common electronic materials emit laser beams.
The phenomenon was discovered, by a Princeton University led team, in a type of device called quantum cascade laser, in which an electric current flowing through a specially designed material produces a laser beam.
“This discovery provides a new insight into the physics of lasers,” said Claire Gmachl, director of the Mid-Infrared Technologies for Health and the Environment (MIRTHE) center.
Gmachl’’s group discovered that a quantum cascade laser they had built generated a second beam with very unusual properties, including the need for less electrical power than the conventional beam.
“If we can turn off the conventional beam, we will end up with a better laser, which makes more efficient use of electrical power,” said Gmachl.
The laser used in the Princeton study is a special type called a quantum cascade laser. Built at Princeton University’’s nanofabrication facility, the device is about one-tenth as thick as a human hair and 3 millimeters long.
Despite its tiny size, it is made of hundreds of layers of different semiconductor materials. Each layer is only a few atoms thick.
In this device, electrons “cascade” down through the layers as they lose energy and give off synchronized photons.
The new laser phenomenon has some interesting features.
For instance, in a conventional laser relying on low momentum electrons, electrons often reabsorb the emitted photons, and this reduces overall efficiency.
In the new type of laser, however, this absorption is reduced by 90 percent, according to Gmachl’’s graduate student Kale Franz, who built the laser that revealed the new phenomenon.
This could potentially allow the device to run at lower currents, and also makes it less vulnerable to temperature changes.
“It should let us dramatically improve laser performance,” said Franz.
Unlike other lasers, quantum cascade lasers operate in the mid- and far-infrared range, and can be used to detect even minute traces of water vapor, ammonia, nitrogen oxides, and other gases that absorb infrared light.
As a result, these devices are finding applications in air quality monitoring, medical diagnostics, homeland security, and other areas that require extremely sensitive detection of different chemicals.
“The new discovery should help make these devices smaller, more efficient, and more sensitive,” said Gmachl. (ANI)

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