What are Gas lasers?

A gas laser is a type of laser that uses the gaseous mixture as the active gain medium and emits light when the electric current is discharged through the gas mixture. Gas lasers provide higher optical power than diode-pumped solid-state lasers and operate at a wavelength that is difficult to obtain when using solid-state lasers. It has high beam quality than solid-state laser and offers other advantages such as the inexpensive active material and easy heat removal from the cavity. For example, In CO2 laser, the hydrogen (H2), water vapor, and/or xenon (Xe) help to reoxidize the carbon monoxide (formed in the discharge) to the carbon dioxide.

Construction details of a gas laser (Example: He: Ne laser)

A gas laser has a sealed cavity that contains laser medium and reflective mirrors at the end forming a Fabry-Perot resonator. Gas lasers are pumped electrically and chemically and operate in both continuous wave (CW) and pulsed wave. In pulsed mode operation, they can emit the pulse with the duration in a nanosecond (10⁻⁹ s) or picosecond (10⁻¹² s) or femtosecond (10⁻¹⁵ s) range.

Helium-neon (He: Ne) laser: A helium-neon laser is a type of gas laser that uses a mixture of 90% helium and 10% neon as the gain medium. It emits light that operates at a wavelength of 632.8 nm (red), 543.5 nm (green), 594.1 nm (yellow), 611.9 nm (orange), 3.39 μm, or 1.15 μm. Electrical pumping is the technique used in the He: Ne laser. They are ideal for college laboratory (632.8 nm (red)), interferometry, holography, spectroscopy, barcode scanning, alignment, and optical demonstration applications.

Carbon-dioxide laser (CO2 laser): A CO2 is a type of gas laser that uses a mixture of 15% nitrogen,15% CO2, 70% helium, and possibly some water vapor or xenon (Xe). It operates at a wavelength from 9-11μm.  They have wall-plug efficiency (electrical to optical efficiency) of more than 10 % and use an electrical pumping technique to pump the CO2 laser. They are ideal for material processing, laser cutting, laser beam welding, surgery, dental laser, and military laser applications.

Argon-ion laser: Argon-ion laser is a type of ion laser that uses the noble gas (ionized gas) as a gain medium. Like other lasers, an ion laser also has a sealed cavity that contains a laser medium and mirrors at the end forming a Fabry-Perot resonator. Electrical pumping is the technique that is used to pump the argon-ion laser. They operate at a wavelength ranging from ultraviolet to visible spectrum that includes 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. These lasers are ideal for Retinal phototherapy (for diabetes), lithography, confocal microscopy, and spectroscopy applications.

Krypton laser: The krypton laser is similar to the argon-ion laser. The krypton laser uses ions of krypton as an active gain medium. It operates at 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 wavelengths. The krypton lasers are ideal for scientific research, mixed with argon to create "white-light" lasers, and light shows applications.

Carbon monoxide lasers (CO lasers): The carbon monoxide (CO) laser is a type of gas laser in which CO acts as the laser gain medium. As compare to the CO2 laser, the CO laser offer more wall-plug efficiency in the order of 40 %. Hence, it is more power-efficient than CO2 lasers. CO lasers operate from 2.6 to 4 μm and 4.8 to 8.3 μm wavelength and use an electrical pumping technique to pump itself. They are ideal for material processing,  engraving, welding, cutting of glasses, and photoacoustic spectroscopy applications.  

Excimer laser: It is a pulsed ultraviolet laser that uses a combination of noble gas compounds (ArF [193 nm], KrCl [222 nm], KrF [248 nm], XeCl [308 nm], and XeF [351 nm] and reactive gas (fluorine or chlorine). The excimer lasers emit laser light in the ultraviolet region and are ideal for ultraviolet lithography for semiconductor manufacturing, laser surgery, and LASIK applications.

Nitrogen laser: The nitrogen laser is another type of pulsed ultraviolet laser that operates at a wavelength of 337.1 nm. The gain medium is pure nitrogen and is pumped by electrical discharge. The wall-plug efficiency of this laser is comparatively low and is in the order of 0.1 %. The nitrogen laser is ideal for pumping dye lasers, measuring air pollution, and scientific research applications

Hydrogen lasers: This laser operates at 116 nm, 123 nm, or 160 nm wavelength.

Metal vapor lasers: This is a type of gas laser that uses metal vapor as the laser gain medium and is pumped electrically. The copper vapor laser operates at a wavelength of 510.6 nm (green) or 578.2 nm (yellow) and delivers an output power of up to 100 W. The Helium-cadmium laser is very similar to the Helium-neon laser and operates at a wavelength of 442 nm (blue) or 325 nm (ultraviolet) and delivers an output power of up to 100 mW. The alkali vapor laser is another type of vapor laser that uses a cesium or rubidium cell in an oven as the active laser medium. The power efficiency and beam quality of alkali vapor laser are fairly high and hence, it is used as an efficient brightness converter.

Chemical laser: The chemical laser is a type of gas laser that converts the chemical energy of gases into continuous wave laser energy. It operates in the mid-near-infrared region. The chemical laser delivers power up to the megawatt level. For example, the hydrogen fluoride laser (2.7–2.9 µm) and the deuterium fluoride laser (3.8 µm). The chemical lasers are ideal for anti-missile weapons and industrial applications.

Specifications details of gas lasers

Technology: Gas laser

Tunable: Represents the wavelength tune-ability of the gas lasers. These lasers are available both in tuneable and non-tuneable options.

Fiber-coupled: The gas lasers are available both in fiber couple or non-fiber coupled options.

Operation mode: Represents the operation mode. The gas lasers are available both in continuous wave (CW) and pulsed mode operation. The pulse laser is also called a q-switched laser.

Wavelength: Represents the wavelength of laser light emitted from a gas laser. These lasers are available from the far UV range (200 nm down to 10 nm) to the IR range (10600 nm). The wavelength is represented in a micrometer (µm) or in nanometre (nm). For example, the lasers emit laser light in the ultraviolet region (193 nm to 351 nm), and a CO₂ laser emit laser light in the infrared region (10600 nm).

Laser color: The gas lasers can emit light with UV range to infrared range.

Gain medium type: Gas

Laser gain medium: Based on the type of gas laser, the gain medium of a gas laser may be the He:Ne / CO/CO₂/ Hydrogen/Nitrogen/ F2/ ArF/ KrF/ XeCl/ XeF/noble gas/ CH4/ H2S/ NH3/…,etc.