Gas laser

A gas laser is a laser in which an electric current is discharged through a gas to produce 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, was co-invented by Iranian physicist Ali Javan and American physicist William R. Bennett, Jr. in 1960.

Types of gas laser

Gas lasers using many gases have been built and used for many purposes.

The helium-neon laser (HeNe) emits at a variety of wavelengths and units operating at 633 nm are very common in education because of its low cost.

Carbon dioxide lasers can emit hundreds of kilowatts[1] 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%.

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.

A nitrogen transverse electrical discharge in gas at atmospheric pressure (TEA) laser is an inexpensive gas laser producing UV light at 337.1 nm.[2]

Metal ion lasers are gas lasers that generate deep ultraviolet wavelengths. Helium-silver (HeAg) 224 nm and neon-copper (NeCu) 248 nm are two examples. These lasers have particularly narrow oscillation linewidths of less than 3 GHz (0.5 picometers),[3] making them candidates for use in fluorescence suppressed Raman spectroscopy.

* Helium-neon laser
* Nitrogen laser
* Carbon dioxide laser
* Ion laser
* Gas dynamic laser

Chemical lasers

Chemical lasers are powered by a chemical reaction, and can achieve high powers in continuous operation. For example, in the Hydrogen fluoride laser (2700-2900 nm) and the Deuterium fluoride laser (3800 nm) 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.

Excimer lasers

Excimer lasers are powered by a chemical reaction involving an excited dimer, or excimer, 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 light, and are used in semiconductor photolithography and in LASIK eye surgery. Commonly used excimer molecules include F2 (fluorine, emitting at 157 nm), and noble gas compounds (ArF [193 nm], KrCl [222 nm], KrF [248 nm], XeCl [308 nm], and XeF [351 nm]).[4]

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

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 the Bar Code which is imprinted on the product. They have been largely replaced by laser diodes.

See also

* Brewster window

References

1. ^ "Air Force Research Lab's high power CO2 laser". Defense Tech Briefs. http://www.afrlhorizons.com/Briefs/Feb04/ML0315.html.
2. ^ Csele, Mark (2004). "The TEA Nitrogen Gas Laser". Homebuilt Lasers Page. http://www.technology.niagarac.on.ca/people/mcsele/lasers/LasersTEA.htm. Retrieved 2007-09-15.
3. ^ "Deep UV Lasers" (PDF). Photon Systems, Covina, Calif. http://www.photonsystems.com/pdfs/duv-lasersource.pdf. Retrieved 2007-05-27.
4. ^ Schuocker, D. (1998). Handbook of the Eurolaser Academy. Springer. ISBN 0412819104.

* Yariv, Amnon (1989). Quantum Electronics (3rd Edition ed.). Wiley. ISBN 0-4716-0997-8.
* http://www.google.com/patents/about?id=r2pmAAAAEBAJ&dq=3,149,290 Patent #3,149,290