Teamwork yields highest operating temp for a terahertz quantum cascade laser

April 2, 2008, Leeds, UK--A collaboration between the Universities of Leeds and Harvard is bringing a handheld terahertz device closer to reality.

April 2, 2008, Leeds, UK--A collaboration between the Universities of Leeds and Harvard is bringing a handheld terahertz device closer to reality. The Leeds team, led by Professors Edmund Linfield and Giles Davies from the Faculty of Engineering, has recorded the highest operating temperature for a terahertz quantum cascade laser, which scientists believe may unlock the potential of the terahertz frequency range.

"The potential uses for terahertz technology are huge, but at the moment they are limited to niche applications in, for example, the pharmaceutical industry and astronomy, as the current systems on the market are expensive and physically quite large," Linfield explains. "The availability of cheap, compact systems would open up a wide range of opportunities in fields including industrial process monitoring, atmospheric science, and medicine."

Key to exploiting terahertz technology is the production of handheld devices, and it is believed that the quantum cascade laser will allow the creation of a terahertz device that is small and portable. The problem is, at the moment this type of laser will only function at temperatures of minus 100°C.

So the challenge is to create a terahertz quantum cascade laser which will work at room temperature. While the groups from Leeds and Harvard are still a ways off from this, they have succeeded in increasing the laser's operating temperature by nearly 10 degrees and believe they have the means to improve it yet further.

"We hope to obtain further advances by optimizing the methods we used to create the device," Linfield says. "We have some radically new design ideas, and also believe that we can make significant improvements in the way we fabricate the lasers."

Terahertz quantum cascade lasers are created by building layers of compounds of aluminium, gallium. and arsenic one atomic monolayer at a time, through a process known as molecular beam epitaxy. Leeds' Faculty of Engineering is one of a small number of laboratories in the world actively growing terahertz quantum cascade lasers at this time, using a molecular beam epitaxy system purchased through the Science Research Infrastructure Fund (SRIF).

The research, carried out in collaboration with the group of Professor Frederico Capasso at Harvard University, and supported by the Engineering and Physical Sciences Research Council (EPSRC) is published in Optics Express (Vol. 16, Issue 5, pp. 3242-3248).

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