Gas laser
   HOME

TheInfoList



OR:

A gas laser is a
laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fi ...
in which an electric current is discharged through a
gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
to produce coherent light. The gas laser was the first continuous-light laser and the first laser to operate on the principle of converting electrical energy to a laser light output. The first gas laser, the
Helium–neon laser A helium–neon laser or He-Ne laser, is a type of gas laser whose high energetic medium gain medium consists of a mixture of 10:1 ratio of helium and neon at a total pressure of about 1 torr inside of a small electrical discharge. The bes ...
(HeNe), was co-invented by Iranian-American engineer and scientist
Ali Javan Ali Javan ( fa, علی جوان, Ali Javān; December 26, 1926 – September 12, 2016) was an Iranian-American physicist and inventor. He was the first to propose the concept of the gas laser in 1959 at the Bell Telephone Laboratories. A successf ...
and American physicist William R. Bennett, Jr., in 1960. It produced a coherent light beam in the infrared region of the spectrum at 1.15 micrometres.


Types of gas laser

Gas lasers using many gases have been built and used for many purposes.
Carbon dioxide laser The carbon-dioxide laser (CO2 laser) was one of the earliest gas lasers to be developed. It was invented by Kumar Patel of Bell Labs in 1964 and is still one of the most useful types of laser. Carbon-dioxide lasers are the highest-power contin ...
s, or CO2 lasers can emit hundreds of kilowatts at 9.6  µm and 10.6 µm, and are often used in industry for cutting and welding. The efficiency of a CO2 laser is over 10%.
Carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
or "CO" lasers have the potential for very large outputs, but the use of this type of laser is limited by the toxicity of carbon monoxide gas. Human operators must be protected from this deadly gas. Furthermore, it is extremely corrosive to many materials including seals, gaskets, etc. Helium–neon (HeNe) lasers can be made to oscillate at over 160 different wavelengths by adjusting the cavity Q to peak at the desired wavelength. This can be done by adjusting the spectral response of the mirrors or by using a dispersive element (
Littrow prism In optics, a Littrow prism or Littrow spectrograph or Littrow mirror is a retro-reflecting dispersing prism arranged in such a way that an incident light beam which enters at the Brewster angle undergoes minimal deviation and hence maximum dispers ...
) in the cavity. Units operating at 633 nm are very common in schools and laboratories because of their low cost and near-perfect beam qualities.
Nitrogen laser A nitrogen laser is a gas laser operating in the ultraviolet rangeC. S. Willett, ''Introduction to Gas Lasers: Population Inversion Mechanisms'' (Pergamon, New York,1974). (typically 337.1 nm) using molecular nitrogen as its gain medium, pu ...
s operate in the ultraviolet range, typically 337.1 nm, using molecular nitrogen as its gain medium, pumped by an electrical discharge.
TEA laser A TEA laser is a gas laser energized by a high voltage electrical discharge in a gas mixture generally at or above atmospheric pressure. The most common types are carbon dioxide lasers and excimer lasers, both used extensively in industry and r ...
s are energized by a high voltage electrical discharge in a gas mixture generally at or above atmospheric pressure. The acronym "TEA" stands for Transversely Excited Atmospheric.


Chemical lasers

Chemical laser A chemical laser is a laser that obtains its energy from a chemical reaction. Chemical lasers can reach continuous wave output with power reaching to megawatt levels. They are used in industry for cutting and drilling. Common examples of chemical ...
s are powered by a chemical reaction and can achieve high powers in continuous operation. For example, in the
hydrogen fluoride laser The hydrogen fluoride laser is an infrared chemical laser. It is capable of delivering continuous output power in the megawatt range. Hydrogen fluoride lasers operate at the wavelength of 2.7-2.9  µm. This wavelength is absorbed by the atmos ...
(2.7–2.9 µm) and the
deuterium fluoride laser The hydrogen fluoride laser is an infrared chemical laser. It is capable of delivering continuous output power in the megawatt range. Hydrogen fluoride lasers operate at the wavelength of 2.7-2.9 µm. This wavelength is absorbed by the atmosph ...
(3.8 µm) the reaction is the combination of hydrogen or deuterium gas with combustion products of ethylene in nitrogen trifluoride. They were invented by
George C. Pimentel George Claude Pimentel (May 2, 1922 – June 18, 1989) was the inventor of the chemical laser. He also developed the technique of matrix isolation in low-temperature chemistry. In theoretical chemistry, he proposed the three-center four-electron ...
. Chemical lasers are powered by a chemical reaction permitting a large amount of energy to be released quickly. Such very high power lasers are especially of interest to the military. Further, continuous-wave chemical lasers at very high power levels, fed by streams of gasses, have been developed and have some industrial applications.


Excimer lasers

Excimer lasers are powered by a chemical reaction involving an ''excited dimer'', or ''
excimer An excimer (originally short for excited dimer) is a short-lived dimeric or heterodimeric molecule formed from two species, at least one of which has a valence shell completely filled with electrons (for example, noble gases). In this case, form ...
'', which is a short-lived dimeric or heterodimeric molecule formed from two species (atoms), at least one of which is in an excited electronic state. They typically produce
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
light, and are used in semiconductor photolithography and in
LASIK LASIK or Lasik (''laser-assisted in situ keratomileusis''), commonly referred to as laser eye surgery or laser vision correction, is a type of refractive surgery for the correction of myopia, hyperopia, and an actual cure for astigmatism, sinc ...
eye surgery. Commonly used excimer molecules include F2 ( fluorine, emitting at 157 nm), and noble gas compounds (ArF 93 nm KrCl 22 nm KrF 48 nm XeCl 08 nm and XeF 51 nm.


Ion lasers

Argon-ion lasers emit light in the range 351–528.7 nm. Depending on the optics and the laser tube a different number of lines is usable but the most commonly used lines are 458 nm, 488 nm and 514.5 nm.


Metal-vapor lasers

Metal-vapor lasers are gas lasers that typically generate
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
wavelengths.
Helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
-
silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
(HeAg) 224 nm, neon-
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
(NeCu) 248 nm and
helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
-
cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
(HeCd) 325 nm are three examples. These lasers have particularly narrow oscillation
linewidth A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...
s of less than 3 
GHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
(500
femtometer The magnitudes_.html" ;"title="Magnitude_(mathematics).html" ;"title="atom.html" ;"title="helium helium_atom_and_perspective_Magnitude_(mathematics)">magnitudes_">Magnitude_(mathematics).html"_;"title="atom.html"_;"title="helium_atom">helium_a ...
s), making them candidates for use in
fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
suppressed Raman spectroscopy. The
Copper vapor laser Copper vapor laser (CVL) uses vapors of copper as the lasing medium in a 4-level laser. It produces green laser light at 510.6 nm and yellow laser light at 578.2 nm. The pulse width is typically from 5 to 60 ns, and peak power from 50 ...
, with two spectral lines of green (510.6 nm) and yellow (578.2 nm), is the most powerful laser with the highest efficiency in the visible spectrum.


Advantages

* High volume of active material * Active material is relatively inexpensive * Almost impossible to damage the active material * Heat can be removed quickly from the
cavity Cavity may refer to: Biology and healthcare *Body cavity, a fluid-filled space in many animals where organs typically develop **Gastrovascular cavity, the primary organ of digestion and circulation in cnidarians and flatworms *Dental cavity or too ...


Applications

* He-Ne laser is mainly used in making holograms. * In laser printing He-Ne laser is used as a source for writing on the photosensitive material. * He-Ne lasers were used in reading Bar Codes, which are imprinted on products in stores. They have been largely replaced by
laser diodes The laser diode chip removed and placed on the eye of a needle for scale A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with e ...
. * Nitrogen lasers and excimer laser are used in pulsed dye laser pumping. * Ion lasers, mostly argon, are used in CW dye laser pumping.


See also

*
Gas dynamic laser A gas dynamic laser (GDL) is a laser based on differences in relaxation velocities of molecular vibrational states. The lasing medium gas has such properties that an energetically lower vibrational state relaxes faster than a higher vibrational st ...
*
Brewster window Brewster's angle (also known as the polarization angle) is an angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with ''no reflection''. When ''unpolarized'' light ...
*
List of laser types This is a list of laser types, their operational wavelengths, and their applications. Thousands of kinds of laser are known, but most of them are used only for specialized research. Overview Gas lasers Chemical lasers Used as directed-ener ...


References

* * http://www.google.com/patents/about?id=r2pmAAAAEBAJ&dq=3,149,290 Patent #3,149,290 {{Lasers American inventions