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Excerpt from Field Guide to Lasers
There are several lasers that use some gas as a laser gain medium. Even though such lasers greatly differ in terms of physical principles, emission wavelength, efficiency, and output power, they share certain aspects:
- Most gas lasers are pumped with an electrical discharge and thus require a high-voltage supply, often with high electrical power.
- Despite their low densities, gases can generate high optical gains due to their large emission cross sections (on "allowed" transitions). On the other hand, optical beam distortions caused by the gas are usually small.
- Gases are rather robust gain media, not prone to the problems associated with solids, such as fractures or defect creation. They may, however, be chemically modified or contaminated during laser operation, resulting in a limited lifetime, particularly for devices operating with high electrical current densities.
The most important types of gas lasers are discussed on the following pages and briefly listed here:
- Helium-neon lasers generate milliwatt powers at visible or infrared wavelengths, often with a narrow linewidth and good frequency stability.
- Argon- and krypton-ion lasers can generate multiwatt visible laser output with good beam quality but with poor power efficiency.
- Carbon-dioxide lasers are relatively efficient sources for 10.6-µm laser radiation and are widely used for material processing.
- Excimer lasers are powerful pulsed ultraviolet lasers.