定义：
利用氩离子中气体放电实现光放大的气体激光器。

氩离子激光器是功率很高的气体激光器，通常可以产生几瓦特的绿光或者蓝光，光束质量很高。 
氩离子激光器的核心部件就是充满氩气的管子，是由氧化铍陶瓷做成的，在其中两个空心电极之间产生很强的气体放电，从而产生很高密度的氩离子等离子体。管子周围的罗西安全可以用来产生磁场，通过更好的限制等离子体来提高输出功率。 

图1:20W氩离子激光器的装置图。其中具有很高电流强度的气体放电发生在空心阳极和阴极之间。腔内棱镜可以旋转从而能够选择工作波长。 
通常装置包含一个长度为1m的管子，产生10W到20W的输出功率，光谱在514.5nm的绿光区域，需要几十千瓦的电动率。（管子中的电压降约为100V或者几百V，电流可能为几十安培。）需要采用水流来移除耗散的热，闭环冷却系统通常包括一个制冷机，这会进一步增大能量消耗。总的电光转换效率通常比较低，一般小于0.1%。还有更小型的气体冷却氩离子激光器，可以产生几十毫瓦的输出功率，消耗的电功率为几百瓦特。 
激光器还可以通过选装腔内棱镜调整输出波长为457.9nm（蓝光），488.0nm（蓝绿光）或者351nm（紫外光）。最高的输出功率为514.5nm波长处。如果没有腔内棱镜，氩离子激光器会同时产生多个波长的光。 
还有一种类似的气体激光器采用的是氪气。氪离子激光器通常辐射647.1nm，413.1nm或者530.9nm的光，还有其它可见光区域的光，也可以得到紫外光和红外光谱。 
其它种类的离子激光器在词条气体激光器中提及到了。 

应用 
几瓦特的氩离子激光器可用于泵浦钛蓝宝石激光器和染料激光器，或者激光表演。与之相竞争的是倍频二极管泵浦固态激光器。后者功率效率更高，并且寿命更长，但是价格更贵。氩气管的寿命只有几百个小时。因此，氩离子激光器适用于只工作在有限时间的应用中，而二极管泵浦固态激光器则适用于长期高效的工作情况下。 
激光安全问题来自于离子激光器的高输出功率和管子上施加的高电压。

Definition: gas lasers based on light amplification in ionized argon in a gas discharge

More general terms: ion lasers, gas lasers

Argon ion lasers are ion lasers, which typically generate multiple watts of optical power in a green or blue output beam with high beam quality. They are the most common ion lasers, and can produce the highest output powers of those. Usually, they are used in continuous-wave operation, although pulsed operation (typically with microsecond pulse durations) is possible.

Argon Ion Laser Tubes

The core component of an argon ion laser is an argon-filled tube, made e.g. of beryllium oxide ceramics, in which an intense electrical discharge between two hollow electrodes generates a plasma with a high density of argon (Ar⁺) ions. A solenoid (electromagnet coil) around the tube (not shown in Figure 1) is normally used for generating a magnetic field (with a strength of e.g. 0.1 T), which increases the output power by better confining the plasma. It is particularly important for high-power and UV versions. Brewster windows are used at the ends.

The outer walls of the tube are generally water-cooled, as they would otherwise get far too hot; low-power versions, however, (e.g. with <100 mW output) can be air-cooled.

Figure 1: Simplified setup of a 20-W argon ion laser. The gas discharge with high current density occurs between the hollow anode and cathode. The intracavity prism can be rotated to select the operation wavelength.

The intense electric current is associated with a substantial gas pumping effect. In a simple cylindrical laser tube, this leads to a substantial pressure gradient along the tube, which is detrimental for the gas discharge. Therefore, one often uses a tube with a gas return path. Earlier versions had a return tube visible from outside, made long enough to avoid an electric discharge in that region. More modern designs have the return path integrated in the tube, not seen from outside.

Laser Resonator

The laser resonator is normally a simple two-mirror resonator, little longer than the laser tube. The fundamental mode radius approximately matches the diameter of the plasma, so that single transverse mode operation is achieved. A dispersive prism can be inserted for selecting one of the laser lines (see below).

A resonator frame, made of low-thermal-expansion material, keeps the mirrors stably aligned despite the varying temperatures. Active mirror positioning and an adjustable optical aperture for mode control may also be used.

The obtained laser gain is quite high – of the order of 10 dB/m; it rises steeply with increasing current density. Parasitic resonator losses e.g. from Brewster windows are therefore not of particularly high concern; one can use an output coupler mirror with relatively high transmissivity.

Typical Output Power and Power Consumption

A typical high-power argon ion laser, containing a tube with a length of the order of 1 m, can generate 10 W or 20 W of output power in the green spectral region at 514.5 nm or a couple of somewhat shorter wavelengths It requires several tens of kilowatts of electric power. (The voltage drop across the tube may be 100 V or a few hundred volts, whereas the current can be several tens of amperes.) The dissipated heat must be removed with a water flow around the tube; a closed-circle cooling system often contains a chiller, which further adds to the power consumption. The total wall-plug efficiency is thus very low, usually below 0.1%.

Laser Lifetime

Relatively frequent replacement of the expensive argon laser tube together with the high electricity consumption makes the operation quite expensive!

Due to the extreme conditions in the high-density electric discharge, the lifetime of an argon laser tube is unfortunately limited to at most a few thousand hours. Problems result from ion sputtering, causing a deterioration of the electrodes and also a loss of gas pressure. Another challenge arises from intense ultraviolet light, which degrades optical materials and seals.

Due to the sophisticated construction, replacement tubes are quite expensive. This together with the high electricity consumption leads to quite high operation cost.

Low-power Argon Lasers

There are also simpler and smaller air-cooled argon ion lasers, generating some tens or hundreds of milliwatts of output power from several hundred watts of electric power. They do not need water cooling, also normally no electromagnet. However, the natural operation characteristics of argon ion lasers favor devices with output powers of several watts: power efficiencies are worse for low-power devices.

Wavelength Selection

The laser can be switched to other wavelengths such as 457.9 nm (blue), 488.0 nm (blue–green), or 351 nm (ultraviolet) by rotating the intracavity prism (on the right-hand side). The highest output power is achieved on the standard 514.5-nm line. Without an intracavity prism, argon ion lasers have a tendency for multi-line operation with simultaneous output at various wavelengths. All these transitions are 4p → 4s transitions of Ar⁺ ions between different sublevels, with two possible lower laser levels, both being quite short-lived. Ultraviolet Ar ion lasers can also use Ar²⁺ ions as laser-active agents.

Note that while single-line operation is relatively easily achieved, single frequency operation is difficult because of the substantial Doppler-broadened linewidth of the laser transitions in combination with the small free spectral range of the long laser resonator.

There are similar noble gas ion lasers based on krypton instead of argon. Krypton ion lasers typically emit at 647.1 nm or on some other lines mostly in the visible spectral region – green, yellow or blue.

Warm-up Time

Due to the substantial heating of the tube, a relatively long warm-up time is often required for achieving stable operation. That also contributes to the high electricity consumption.

Safety

Laser safety issues arise both from the high output power of typical ion lasers and from the high voltage applied to the tube.

Applications

Multi-watt argon ion lasers can be used e.g. for pumping titanium–sapphire lasers and dye lasers, or for laser light shows. However, they have been more and more replaced with frequency-doubled diode-pumped solid-state lasers. The latter are far more power efficient and have longer lifetimes, but are more expensive. An argon laser may thus be preferable if it is used only during a limited number of hours, whereas a diode-pumped solid-state laser is the better solution for reliable and efficient long-term operation.

In earlier years, argon ion lasers with their ability to generate multiple watts at various wavelengths in the visible spectral region where often chosen for laser shows.

Other applications were in Raman spectroscopy, particle flow velocimetry, forensic medicine, holography, wafer inspection and lithography in the semiconductor industry, lithographic fabrication of CD masters, and laser printers. There are also medical applications such as retinal phototherapy. One may also treat diabetes-related retinal detachment of the retina.

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