Compiled by Photonics Spectra staff
For the first time, terahertz rays, or T-ray pulses, have been made to emit separate
“packets” of terahertz radiation – rather than one continuous
beam – from a quantum cascade laser. The finding could open new doors for
T-rays to image natural and synthetic materials.
Researchers from Denis Diderot University in Paris, the French
National Centre for Scientific Research and the University of Leeds in the UK published
their work online April 24, 2011, in Nature Photonics (doi: 10.1038/nphoton.2011.49).
The term “T-ray” describes a band of radiation in
the electromagnetic spectrum that falls between radio waves and visible light. T-rays
can be used to detect impurities in chemical and biological materials, generating
characteristic “spectral fingerprints” that can identify various substances.
Recently, scientists have become interested in a technique known
as terahertz time-domain spectroscopy, a particularly sensitive way of probing materials
using pulses of T-rays. Until now, these pulses were made using laser sources that
generated very little power – about one-millionth of a watt).
Harnessing the power of a quantum cascade laser that is almost 10,000 times more powerful than previous versions, researchers have developed a T-ray pulse train, an advance that
confirms the technique could be used for probing materials.
In this latest work, the scientists harnessed the power of a quantum
cascade laser (almost 10,000 times more powerful than previous versions) to create
a train of T-ray pulses. They also devised a way of detecting the full pulse train,
confirming that the technique could be used for probing materials.
“The potential for T-rays to provide new imaging and spectroscopy
techniques for a range of applications, such as chemical and atmospheric sensing
or medical imaging, is immense,” said Edmund Linfield, a professor at the
University of Leeds’ School of Electronic and Electrical Engineering.
The research was supported by the Délégation Générale
pour l’Armement, the National Agency for Research, the UK Engineering and
Physical Sciences Research Council, and European Research Council programs NOTES
and TOSCA.