Press releases
Please quote Nature Physics as the source of these items.
The April 2007 issue of Nature Physics is available online.
April 2007
Turning up the heat on terahertz lasers
Compact room-temperature terahertz lasers for medical imaging, airport security and many other applications could soon be available, suggests an article in the May issue of Nature Physics. Romain Terazzi and colleagues modified a quantum cascade laser (QCL) — one of the most promising compact sources of terahertz radiation — to operate in a qualitatively different way from that of most conventional lasers.
QCLs have been around for over a decade, but because of their electrically unstable nature, those that emit in the terahertz region have so far only been able to operate at temperatures of around -173°C. The new device uses an electrical pumping mechanism known as 'Bloch gain', which reduces the threshold at which lasing occurs, and enables the laser to be operated at lower electrical currents and, in turn, with greater stability at temperatures approaching room temperature.
Terahertz radiation lies in a difficult to reach part of the optical spectrum between microwaves and the infrared. It is non-ionizing, and so doesn't have the potential health risks associated with X-rays, and can pass through many everyday materials such as clothing, plastics and wood. These characteristics, combined with the unique absorption signature of most materials to terahertz radiation, make it particularly useful for detecting weapons, explosives, and drugs at air- and seaports.
Bloch gain in quantum cascade lasers
Romain Terazzi, Tobias Gresch, Marcella Giovannini, Nicolas Hoyler, Norihiko Sekine and J´erome Faist
Published online: 1st April 2007 | doi 10.1038/nphys577