Nano-Biotechnology

New Quantum Cascade Laser Created!

Researchers improve QCL design

By Gabriel Gache, Science News Editor

8th of February 2008, 12:07 GMT

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Image of a typical Quantum Cascade Laser semiconductor chip (right-down corner of the image)

Quantum Cascade Laser systems represent semiconductor lasers that have the ability to emit light in the mid and far-infrared wavelengths of the electromagnetic systems. They are usually used to make spectroscopic analysis, such as measuring gases concentration in the Earth's atmosphere, as sensors for cruise control systems when the visibility is low, home security systems and many other medical and industrial applications. They were initially demonstrated by Federico Capasso at Bell Labs, in 1994, and became commercially available a decade later.

Now, a team of researchers conducted by Federico Capasso, the original inventor

of the first Quantum Cascade Laser, claim to have created a sensor with faster detection capabilities and wider range of chemical sensing, which can detect from infinitesimal concentrations of gases to liquids.

The team obtained a broad tunning of the emission wavelengths of the QCL material, in a commercial reactor used for the mass production of semiconductor lasers, by controlling the size of nanoscale quantum wells, created in the active region of the semiconductor chip. It is practically build of 32 lasers, emitting light in different wavelengths. Each can be controlled individually and fired in a specific pattern, in order to generate a much wider wavelength spectrum that can be used to detect a large number of chemical substances.

The spectrometer sensor designed at Harvard's School of Engineering has the ability to emit laser radiation in the gap between 8.7 and 9.4 micrometers, the wavelengths at which most of the known molecules experience electromagnetic absorption. Its size and versatility promises to replace the currently-existing bulky infrared spectrometers used in scientific and industrial applications.

Once optimized, it will be able to be ten times more sensitive, so that it will extend even more the number of chemical substance detection, plus the possibility of measuring gas concentrations as low as a few parts per billion.

TAGS:

laser | infrared | light absorption | QCL

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