Princeton researchers discover new typ... (o momentum participate in lasing (prod...)

Princeton researchers discover new type of laser

Date:12/22/2008

o momentum participate in "lasing" (producing laser light). Further, a substantial number of electrons has to attain the same level of energy and momentum be in a so-called "quasi-equilibrium" condition -- before they can participate in laser action. In contrast, studies by Gmachl's group showed that the second laser beam originated from electrons of lower energy, but higher momentum that were not in equilibrium. "It showed, contrary to what was believed, that electrons are useful for laser emission even when they are in highly non-equilibrium states," said Franz.

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%, said Franz. 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," he said.

The device used in the study does not fully attain this level of performance, because the conventional, low-efficiency laser mechanism dominates. To take full advantage of the new discovery, therefore, the conventional mechanism would need to be turned off. The researchers have started to work on methods to achieve this outcome, 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.

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Contact: Steven Schultz
sschultz@princeton.edu
609-258-3617
Princeton University, Engineering School
Source:Eurekalert

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Princeton researchers discover new typ...(o momentum participate in lasing (prod...)