Quantum cascade laser

The quantum cascade laser or QC laser is a unipolar solid state laser which uses electrons as its only charge carrier. The "cascade" is a series of equal energy steps built into the material matrix while the crystal is being grown. When the electrons are transmitted through the laser crystal, they emit one photon at each of these cascade steps, unlike diode lasers which only emit one photon per electron transmitted.

Related Topics:
Unipolar - Laser - Electrons - Cascade - Photon - Diode laser

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The laser was invented and demonstrated by Jerome Faist, Federico Capasso, Deborah Sivco, Carlo Sirtori, Albert Hutchinson, and Alfred Cho at Bell Laboratories in 1994.

Related Topics:
Bell Laboratories - 1994

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It consists of alternating layers of two different semiconductors like GaAs/AlGaAs, for example. The layers are grown on a substrate using a process called molecular beam epitaxy. The emitted wavelength of the laser is determined only by the thickness of the crystal layers and the layer materials itself. This is a great advantage over diode lasers, whose wavelengths depend on the band gap of the given material and is therefore restricted.

Related Topics:
Semiconductors - Molecular beam epitaxy - Wavelength - Band gap

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Often a structure called Distributed Feedback (DFB) is built on top of the laser crystal to prevent it from emitting at another than the desired wavelength.

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The laser's comparably high power, tuning range and room temperature operation make it useful for spectroscopical appplications like the remote sensing of environmental gases and pollutants in the atmosphere. It may eventually be used for vehicular cruise control in conditions of poor visibility, collision avoidance radar, industrial process control, and medical diagnostics such as breath analyzers.

Related Topics:
Gas - Pollutant - Cruise control - Visibility - Radar - Diagnostics - Breath analyzer

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