Physics: Principles and ProblemsChapter 28:
The AtomProblem of the Week (0.0K) | Fingerprinting
Pollution (4.0K)
Shine a light at a molecule and it will absorb certain frequencies.
Therefore, each chemical has an optical absorption fingerprint
by which it can be identified. Chemical identification is important
in such applications as monitoring pollution and detecting illegal
drugs or explosives. In practice, however, scientists have had
trouble making laser chemical identification work because they
didn't have a laser that could emit varying frequencies of light.
At least they didn't have the right type of laser until now.
| Light Amplification by Stimulated Emission of Radiation (0.0K) | Quantum
Cascade Laser
The quantum cascade laser, developed in 1994, is the world's
first laser that can vary the wavelength of the light it emits
over a relatively wide range, from 4 to 12 microns. The reason
for the name, Quantum Cascade, is that QC lasers
operate like an electronic waterfall. A QC laser consists of
many layers of semiconducting material. When an electric current
flows through the laser, electrons cascade down an energy staircase.
At every step, the electrons make a quantum jump between energy
levels and emit a photon in the process. The photons are reflected
back and forth between mirrors, stimulating other quantum jumps
and the emission of other photons. This amplification process
enables a high output power. | (0.0K) | What
is the name of the region of the electromagnetic spectrum where
the QC laser emits radiation? | | (0.0K) | What
is the energy difference between some of the energy levels in
the semiconducting material that makes up the QC laser? | (1.0K) | For
more information on developments of the quantum cascade laser,
go to http://www.lucent.com/ideas2/
inventions/docs/qclaser.html,. Clicking will launch a new
window. | (0.0K) | (0.0K) | (0.0K) | (0.0K) | (0.0K) |
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