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Lasers are used across microelectronic device production, micromachining, and in the medical field. The type of laser used for different applications is governed by the laser or gain medium, meaning the material that is powered by a source of energy to make the light produced stronger. The laser medium can be either solid, liquid, or gas, and it can also be a semiconductor.
Gas lasers are one of the oldest types of laser and have been used for many purposes. A wide range of gases has been used to build gas lasers, which include:
- Helium-Neon (HeNe)
- Carbon Dioxide (CO2)
- Nitrogen (N)
Nitrogen lasers work in the ultraviolet range. They are used in spectroscopy, photochemistry and in microscopy experiments in the life sciences.
Helium-Neon (HeNe) Gas Laser
It is one of the most common gas lasers. HeNe lasers are capable of oscillating at over 160 different wavelengths by adjusting the spectral response of the mirrors or by using a Littrow prism. A helium-neon gas laser is usually built operating in the red with a wavelength of 633 nm. They can also be built to operate in the green and infrared with wavelengths of 544 nm and 1523 nm, respectively. Schools and laboratories make use of HeNe laser units operating at 633 nm for their almost perfect beam quality and affordability.
Carbon Dioxide (CO2) Gas Laser
CO2 lasers are one of the most efficient lasers and are used in industries such as in welding and cutting. The CO2 gas laser operates at numerous infrared frequencies and does not operate in the visible frequency. The efficiency of a CO2 gas laser is said to be more than 30%, and it also has the capability of producing tens and hundreds of kilowatts of continuous output power. The CO2 gas laser also hosts the capability of pulse operations under extremely high power.
Argon-Ion Gas Laser
Argon-Ion is part of the family of lasers using noble gasses as the active medium. They are capable of emitting at 13 wavelengths through both the visible and ultraviolet spectra and as a continuous gas laser. The wavelength ranges from 409 to 686 nm in the visible region. However, argon-ion gas lasers are best known to operate in the green with wavelengths of 488 nm and 514.5 nm, which are its most efficient transitions. Argon-ion lasers work at a much higher power than the helium-neon gas laser.
The blue-green regions of the visible spectra are often used for underwater communication. Argon-ion lasers are used in the medical field for retinal phototherapy to treat complications arising from diabetes. They are also used for lithography and to pump other lasers.
Nitrogen (N) Laser
Nitrogen lasers work in the ultraviolet range. They are used in spectroscopy, photochemistry and in microscopy experiments in the life sciences. Nitrogen lasers with an efficiency of up to 3% have been reported, but generally, the efficiency is low at 0.1% or less. Applications for nitrogen lasers include:
- Transverse optical pumping of dye lasers
- Air pollution measurement
- Matrix-assisted laser desorption/ionization
Chemical lasers are devices that are powered by a chemical reaction. They are also capable of achieving high powers in continuous operation. There are several types of chemical lasers that have been developed:
- Hydrogen fluoride (HF)/deuterium fluoride (DF) laser
- Chemical oxygen iodine laser (COIL)
- All gas-phase iodine laser (AGIL)
Hydrogen Fluoride (HF)/Deuterium Fluoride (DF) Chemical Laser
In the hydrogen fluoride/deuterium fluoride chemical laser, a combustor is used to manufacture the fluorine atoms. The fluorine atoms are then accelerated into the laser cavity through supersonic nozzles. The fluorine atoms are mixed and reacted with the H2 and D2 under low pressure and low-temperature environments to form excited states of HF and DF.
Hydrogen fluoride lasers operate in the wavelengths of 2700 to 2900 nm, while deuterium fluoride lasers operate in the wavelengths of 3800 nm. Deuterium fluoride lasers are mainly used for military applications.
Chemical Oxygen Iodine Laser
The chemical oxygen iodine laser (COIL) is produced by the reaction of liquid basic hydrogen peroxide with chlorine gas. The resulting product is an electronically excited oxygen molecule in the gaseous phase. This energy of the excited oxygen molecule is then transferred to the iodine atoms to emit radiation at a wavelength of 1.315 microns.
COIL laser was developed for military purposes. It is also useful in industrial processing applications such as laser cutting and drilling.
All Gas-Phase Iodine Laser (AGIL)
The AGIL laser uses gaseous iodine for its lasing medium. It operates at the 1.315 microns wavelength. AGIL lasers use reactions between chlorine atoms and gaseous hydrazoic acid, which result in excited chloronitrene (NCI) molecules. It was developed to solve problems found with the COIL lasers concerning their aqueous chemistry.
AGIL lasers are easier to work with than COIL lasers as the chemicals used are all in a gaseous state. When used in aerospace, this puts AGIL at a distinct advantage over COIL as the overall weight is a lot lower.
Sources and Further Reading
This article was updated on 11th March, 2019.