An ion laser is a
gas laser
A gas laser is a laser in which an electric current is discharged through a gas 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 lase ...
that uses an
ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
ized gas as its lasing medium.
Like other gas lasers, ion lasers feature a sealed cavity containing the laser medium and mirrors forming a
Fabry–Pérot resonator. Unlike
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 ...
s, the energy level transitions that contribute to laser action come from
ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
s. 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
Cooling tower and water discharge of a nuclear power plant
Water cooling is a method of heat removal from components and industrial equipment. Evaporative cooling using water is often more efficient than air cooling. Water is inexpensive and no ...
. A small air-cooled ion laser might produce, for example, 130
milliwatt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wat ...
s of output light with a tube current of about 10
ampere
The ampere (, ; symbol: A), often shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to elect ...
s 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
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemi ...
krypton
Krypton (from grc, κρυπτός, translit=kryptos 'the hidden one') is a chemical element with the symbol Kr and atomic number 36. It is a colorless, odorless, tasteless noble gas that occurs in trace amounts in the atmosphere and is often ...
as its
gain medium
The active laser medium (also called gain medium or lasing medium) is the source of optical gain within a laser. The gain results from the stimulated emission of photons through electronic or molecular transitions to a lower energy state from a h ...
. The
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 ...
is done by an
electrical discharge
An electric discharge is the release and transmission of electricity in an applied electric field through a medium such as a gas (ie., an outgoing flow of electric current through a non-metal medium).American Geophysical Union, National Research ...
. 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
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
), for the manufacture of security
hologram
Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other Holography#Applications, applic ...
s, 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
![Nci-vol-2268-300 argon ion laser](https://upload.wikimedia.org/wikipedia/commons/e/e6/Nci-vol-2268-300_argon_ion_laser.jpg)
The argon-ion laser was invented in 1964 by William Bridges at the
Hughes Aircraft Company and it is one of the family of ion lasers that use a
noble gas
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemi ...
as the active medium.
Argon-ion lasers are used for
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
l
phototherapy (for the treatment of
diabetes
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
),
lithography
Lithography () is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone (lithographic limestone) or a metal plate with a smooth surface. It was invented in 1796 by the German a ...
, 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. 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.
![Argon laser beam and diffraction mirror](https://upload.wikimedia.org/wikipedia/commons/1/1d/Argon_laser_beam_and_diffraction_mirror.png)
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
Kovar (trademark of CRS Holdings, inc., Delaware) is a nickel–cobalt ferrous alloy compositionally identical to Fernico 1, designed to have substantially the same thermal expansion characteristics as borosilicate glass (~5 × 10−6 /K betwe ...
metal-to-ceramic seals,
beryllium oxide
Beryllium oxide (BeO), also known as beryllia, is an inorganic compound with the formula BeO. This colourless solid is a notable electrical insulator with a higher thermal conductivity than any other non-metal except diamond, and exceeds that of ...
ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
s, or
tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isolat ...
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 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 ...
s, which require just a few milliamperes of input current, the current used for pumping the argon laser is several amperes, since the gas has to be ionized. The ion laser tube produces much
waste heat
Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility ...
, 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/cm
2, 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.
William R. Bennett
William Richards Bennett, (April 14, 1932 – December 3, 2015) was the 27th premier of British Columbia from 1975 to 1986. He was a son of Annie Elizabeth May (Richards) and former Premier, W. A. C. Bennett. He was a 3rd cousin, twice removed, ...
, a co-inventor of the first gas laser (the helium–neon laser), was the first to observe
spectral hole burning
Spectral hole burning is the frequency-selective bleaching of the absorption spectrum of a material, which leads to an increased transmission (a "spectral hole") at the selected frequency.
Two basic requirements must be met for the phenomenon to ...
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
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 ...
), 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
Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
*
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...
*
Oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
Applications
*
Confocal laser scanning microscopy
Confocal microscopy, most frequently confocal laser scanning microscopy (CLSM) or laser confocal scanning microscopy (LCSM), is an optical imaging technique for increasing optical resolution and contrast of a micrograph by means of using a s ...
*
Surgical
Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pat ...
*
Laser medicine
Laser medicine consists in the use of lasers in medical diagnosis, treatments, or therapies, such as laser photodynamic therapy, photorejuvenation, and laser surgery.
Lasers
Lasers used in medicine include in principle any type of laser, bu ...
* High speed typesetters
*
Laser light shows
A laser lighting display or laser light show involves the use of laser light to entertain an audience. A laser light show may consist only of projected laser light beam, beams set to music, or may accompany another form of entertainment, ty ...
*
DNA sequencer
A DNA sequencer is a scientific instrument used to automate the DNA sequencing process. Given a sample of DNA, a DNA sequencer is used to determine the order of the four bases: G (guanine), C (cytosine), A (adenine) and T (thymine). This is the ...
s
*
Spectroscopy
Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...
experiments
*
Pumping dye laser
A dye laser is a laser that uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths, often spanning 50 to 100 ...
s
[ F. J. Duarte and L. W. Hillman (Eds.), ''Dye Laser Principles'' (Academic, New York, 1990) Chapters 3 and 5]
* Semiconductor
wafer inspection
* Direct write high density PCB
lithography
Lithography () is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone (lithographic limestone) or a metal plate with a smooth surface. It was invented in 1796 by the German a ...
*
Fiber Bragg Grating
A fiber Bragg grating (FBG) is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. This is achieved by creating a periodic variation in th ...
production
* Long coherence length models can be used for holography
See also
*
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 fir ...
*
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 ...
*
List of plasma (physics) articles
References
{{Lasers
American inventions
Gas lasers