Far infrared laser
Encyclopedia
Far infrared laser is a laser
with output wavelength
in far infrared part of the electromagnetic spectrum
, between 30-1000 µm (300 GHz - 10 THz). It is one of the possible sources of terahertz radiation
.
FIR lasers have application in terahertz time-domain spectroscopy, terahertz imaging as well in fusion plasma physics diagnostics. They can be used to detect explosives and chemical warfare agents, by the means of infrared spectroscopy
or to evaluate the plasma densities by the means of interferometry techniques.
FIR lasers typically consist of a long (1-3 meters) waveguide
filled with gaseous organic molecules, optically pumped
or via HV discharge. They are highly inefficient, often require helium cooling, high magnetic fields, and/or are only line tunable. Efforts to develop smaller solid-state alternatives are under way.
The p-Ge (p-type germanium) laser is a tunable, solid state, far infrared laser which has existed for over 25 years . It operates in crossed electric and magnetic fields at liquid helium temperatures. Wavelength selection can be achieved by changing the applied electric/magnetic fields or through the introduction of intracavity elements.
Quantum cascade laser
(QCL) is a construction of such alternative. It is a solid-state semiconductor laser that can operate continuously with output power of over 100 mW and wavelength of 9.5 µm. A prototype was already demonstrated. http://dx.doi.org/10.1126/science.264.5158.553 and potential use shown http://www.brightsurf.com/news/headlines/view.article.php?ArticleID=20538.
Free electron laser
s can also operate on far infrared wavelengths.
Femtosecond Ti:sapphire
mode-locked
lasers are also being used to generate very short pulses that can be optically rectified
to produce a terahertz pulse.
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
with output wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
in far infrared part of the electromagnetic spectrum
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
, between 30-1000 µm (300 GHz - 10 THz). It is one of the possible sources of terahertz radiation
Terahertz radiation
In physics, terahertz radiation refers to electromagnetic waves propagating at frequencies in the terahertz range. It is synonymously termed submillimeter radiation, terahertz waves, terahertz light, T-rays, T-waves, T-light, T-lux, THz...
.
FIR lasers have application in terahertz time-domain spectroscopy, terahertz imaging as well in fusion plasma physics diagnostics. They can be used to detect explosives and chemical warfare agents, by the means of infrared spectroscopy
Infrared spectroscopy
Infrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...
or to evaluate the plasma densities by the means of interferometry techniques.
FIR lasers typically consist of a long (1-3 meters) waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
filled with gaseous organic molecules, optically pumped
Laser pumping
Laser pumping is the act of energy transfer from an external source into the gain medium of a laser. The energy is absorbed in the medium, producing excited states in its atoms. When the number of particles in one excited state exceeds the number of particles in the ground state or a less-excited...
or via HV discharge. They are highly inefficient, often require helium cooling, high magnetic fields, and/or are only line tunable. Efforts to develop smaller solid-state alternatives are under way.
The p-Ge (p-type germanium) laser is a tunable, solid state, far infrared laser which has existed for over 25 years . It operates in crossed electric and magnetic fields at liquid helium temperatures. Wavelength selection can be achieved by changing the applied electric/magnetic fields or through the introduction of intracavity elements.
Quantum cascade laser
Quantum cascade laser
Quantum cascade lasers are semiconductor lasers that emit in the mid- to far-infrared portion of the electromagnetic spectrum and were first demonstrated by Jerome Faist, Federico Capasso, Deborah Sivco, Carlo Sirtori, Albert Hutchinson, and Alfred Cho at Bell Laboratories in 1994.Unlike typical...
(QCL) is a construction of such alternative. It is a solid-state semiconductor laser that can operate continuously with output power of over 100 mW and wavelength of 9.5 µm. A prototype was already demonstrated. http://dx.doi.org/10.1126/science.264.5158.553 and potential use shown http://www.brightsurf.com/news/headlines/view.article.php?ArticleID=20538.
Free electron laser
Free electron laser
A free-electron laser, or FEL, is a laser that shares the same optical properties as conventional lasers such as emitting a beam consisting of coherent electromagnetic radiation which can reach high power, but which uses some very different operating principles to form the beam...
s can also operate on far infrared wavelengths.
Femtosecond Ti:sapphire
Ti-sapphire laser
Ti:sapphire lasers are tunable lasers which emit red and near-infrared light in the range from 650 to 1100 nanometers. These lasers are mainly used in scientific research because of their tunability and their ability to generate ultrashort pulses...
mode-locked
Modelocking
Mode-locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds or femtoseconds ....
lasers are also being used to generate very short pulses that can be optically rectified
Optical rectification
Electro-optic rectification is a non-linear optical process which consists in the generation of a quasi-DC polarization in a non-linear medium at the passage of an intense optical beam...
to produce a terahertz pulse.