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An ion laser is a gas laser that uses an ionized gas as its lasing medium.[1] Like other gas lasers, ion lasers feature a sealed cavity containing the laser medium and mirrors forming a Fabry–Pérot resonator. Unlike helium–neon lasers, the energy level transitions that contribute to laser action come from ions. Because of the large amount of energy required to excite the ionic transitions used in ion lasers, the required current is much greater, and as a result all but the smallest ion lasers are water-cooled. A small air-cooled ion laser might produce, for example, 130 milliwatts of output light with a tube current of about 10 amperes and a voltage of 105 volts. Since one ampere times one volt is one watt, this is an electrical power input of about one kilowatt. Subtracting the (desirable) light output of 130 mW from power input, this leaves the large amount of waste heat of nearly one kW. This has to be dissipated by the cooling system. In other words, the power efficiency is very low.

Types
Krypton laser

A krypton laser is an ion laser using ions of the noble gas krypton as its gain medium. The laser pumping is done by an electrical discharge. Krypton lasers are widely used in scientific research, and in commercial uses, when the krypton is mixed with argon, it creates a "white-light" lasers, useful for laser light shows. Krypton lasers are also used in medicine (e.g. for coagulation of retina), for the manufacture of security holograms, and numerous other purposes.

Krypton lasers can emit visible light close to several different wavelengths, commonly 406.7 nm, 413.1 nm, 415.4 nm, 468.0 nm, 476.2 nm, 482.5 nm, 520.8 nm, 530.9 nm, 568.2 nm, 647.1 nm, and 676.4 nm.
Argon laser
This argon-ion laser emits blue-green light at 488 and 514 nm

The argon-ion laser was invented in 1964 by William Bridges at the Hughes Aircraft Company[2] and it is one of the family of ion lasers that use a noble gas as the active medium.

Argon-ion lasers are used for retinal phototherapy (for the treatment of diabetes), lithography, and the pumping of other lasers. Argon-ion lasers emit at 13 wavelengths through the visible and ultraviolet spectra, including: 351.1 nm, 363.8 nm, 454.6 nm, 457.9 nm, 465.8 nm, 476.5 nm, 488.0 nm, 496.5 nm, 501.7 nm, 514.5 nm, 528.7 nm, and 1092.3 nm.[3] However, the most commonly used wavelengths are in the blue-green region of the visible spectrum. These wavelengths have the potential for use in underwater communications because seawater is quite transparent in this range of wavelengths.
An argon-laser beam consisting of multiple colors (wavelengths) strikes a silicon diffraction mirror grating and is separated into several beams, one for each wavelength (left to right): 458 nm, 476 nm, 488 nm, 497 nm, 502 nm, and 515 nm

Common argon and krypton lasers are capable of emitting continuous-wave (CW) output of several milliwatts to tens of watts. Their tubes are usually made from nickel end bells, kovar metal-to-ceramic seals, beryllium oxide ceramics, or tungsten disks mounted on a copper heat spreader in a ceramic liner. The earliest tubes were simple quartz, then followed by quartz with graphite disks. In comparison with the helium–neon lasers, which require just a few milliamperes of input current, the current used for pumping the krypton laser is several amperes, since the gas has to be ionized. The ion laser tube produces much waste heat, and such lasers require active cooling.

The typical noble-gas ion-laser plasma consists of a high-current-density glow discharge in a noble gas in the presence of a magnetic field. Typical continuous-wave plasma conditions are current densities of 100 to 2000 A/cm2, tube diameters of 1.0 to 10 mm, filling pressures of 0.1 to 1.0 Torr (0.0019 to 0.019 psi), and an axial magnetic field of the order of 1000 gauss.[4]

William R. Bennett, a co-inventor of the first gas laser (the helium–neon laser), was the first to observe spectral hole burning effects in gas lasers, and he created the theory of "hole burning" effects in laser oscillation. He was co-discoverer of lasers using electron-impact excitation in each of the noble gases, dissociative excitation transfer in the neon–oxygen laser (the first chemical laser), and collision excitation in several metal-vapor lasers.
Other commercially available types

Ar/Kr: A mix of argon and krypton can result in a laser with output wavelengths that appear as white light.
Helium–cadmium: blue laser emission at 442 nm and ultraviolet at 325 nm.
Copper vapor: yellow and green emission at 578 nm and 510 nm.

Experimental

Xenon[5]
Iodine[6]
Oxygen[7]

Applications

Confocal laser scanning microscopy
Surgical
Laser medicine
High speed typesetters
Laser light shows
DNA sequencers
Spectroscopy experiments
Pumping dye lasers[8]
Semiconductor wafer inspection
Direct write high density PCB lithography
Fiber Bragg Grating production
Long coherence length models can be used for holography

See also

Laser
List of laser types
List of plasma (physics) articles

References

IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "ion laser". doi:10.1351/goldbook.I03219
W. B. Bridges, "LASER OSCILLATION IN SINGLY IONIZED ARGON IN THE VISIBLE SPECTRUM", Applied Physics Letters. 4, 128–130 (1964).
http://www.lexellaser.com/techinfo_gas-ion.htm
Bridges, Halstead et al., Proceedings of the IEEE, 59 (5). pp. 724–739.
Hoffman Toschek, et al., "The Pulsed Xenon Ion Laser: Covers the UV, visible, and near-IR with optics changes", IEEE Journal of Quantum Electronics
Hattori, Kano, Tokutome and Collins, "CW Iodine Ion Laser in a Positive Column Discharge", IEEE Journal of Quantum Electronics, June 1974
Cold Cathode Pulsed Gas Laser" by R. K. Lomnes and J. C. W. Taylor in: Review of Scientific Instruments, vol 42, no. 6, June, 1971.

F. J. Duarte and L. W. Hillman (Eds.), Dye Laser Principles (Academic, New York, 1990) Chapters 3 and 5

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Ion lasers & Metal-vapor lasers
Metal-Vapor

Copper vapor Strontium vapor laser HeCd HeHg HeSe HeAg Au NeCu

Nonmetal Ion

Kr Ar Xe I O

Aspects
Laser cutting

Laser types: Solid-state
Semiconductor Dye Gas
Chemical Excimer Ion Metal Vapor

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Gas lasers

Carbon dioxide Carbon monoxide Helium–neon Nitrogen TEA laser Asterix IV laser ISKRA4,5

Distinct subtypes:

Chemical laser Excimer laser Ion laser Metal-vapor laser

Laser types: Solid-state
Semiconductor Dye Gas
Chemical Excimer Ion Metal Vapor

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Lasers

List of laser articles List of laser types List of laser applications Laser acronyms

Laser types: Solid-state
Semiconductor Dye Gas
Chemical Excimer Ion Metal Vapor

Laser physics

Active laser medium Amplified spontaneous emission Continuous wave Doppler cooling Laser ablation Laser cooling Laser linewidth Lasing threshold Magneto-optical trap Optical tweezers Population inversion Resolved sideband cooling Ultrashort pulse

Laser optics

Beam expander Beam homogenizer B Integral Chirped pulse amplification Gain-switching Gaussian beam Injection seeder Laser beam profiler M squared Mode-locking Multiple-prism grating laser oscillator Multiphoton intrapulse interference phase scan Optical amplifier Optical cavity Optical isolator Output coupler Q-switching Regenerative amplification

Laser spectroscopy

Cavity ring-down spectroscopy Confocal laser scanning microscopy Laser-based angle-resolved photoemission spectroscopy Laser diffraction analysis Laser-induced breakdown spectroscopy Laser-induced fluorescence Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy Raman spectroscopy Second-harmonic imaging microscopy Terahertz time-domain spectroscopy Tunable diode laser absorption spectroscopy Two-photon excitation microscopy Ultrafast laser spectroscopy

Laser ionization

Above-threshold ionization Atmospheric-pressure laser ionization Matrix-assisted laser desorption/ionization Resonance-enhanced multiphoton ionization Soft laser desorption Surface-assisted laser desorption/ionization Surface-enhanced laser desorption/ionization

Laser fabrication

Laser beam welding Laser bonding Laser converting Laser cutting Laser cutting bridge Laser drilling Laser engraving Laser-hybrid welding Laser peening Multiphoton lithography Pulsed laser deposition Selective laser melting Selective laser sintering

Laser medicine

Computed tomography laser mammography Laser capture microdissection Laser hair removal Laser lithotripsy Laser coagulation Laser surgery Laser thermal keratoplasty LASIK Low-level laser therapy Optical coherence tomography Photorefractive keratectomy Photorejuvenation

Laser fusion

Argus laser Cyclops laser GEKKO XII HiPER ISKRA lasers Janus laser Laboratory for Laser Energetics Laser integration line Laser Mégajoule Long path laser LULI2000 Mercury laser National Ignition Facility Nike laser Nova (laser) Novette laser Shiva laser Trident laser Vulcan laser

Civil applications

3D laser scanner CD DVD Blu-ray Laser lighting display Laser pointer Laser printer Laser tag

Military applications

Advanced Tactical Laser Boeing Laser Avenger Dazzler (weapon) Electrolaser Laser designator Laser guidance Laser-guided bomb Laser guns Laser rangefinder Laser warning receiver Laser weapon LLM01 Multiple Integrated Laser Engagement System Tactical High Energy Laser Tactical light ZEUS-HLONS (HMMWV Laser Ordnance Neutralization System)

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