Argon-Ion Lasers

As a distinguished member of the common and well-explored family of ion lasers, the argon-ion laser operates in the visible and ultraviolet spectral regions by utilizing an ionized species of the noble gas argon. Argon-ion lasers function in continuous wave mode when plasma electrons within the gaseous discharge collide with the excited laser species to produce light.

The tutorial initializes with the gas laser applet speed set to Medium, a level that enables the visitor to observe the slow build-up of light in the laser cavity as it is reflected back and forth through the Brewster windows and mirrors. Use the Applet Speed slider to adjust the speed of light oscillations within the laser cavity and the level of light emitted through the output lens.

The argon-ion laser is capable of producing approximately 10 wavelengths in the ultraviolet region and up to 25 in the visible region, ranging from 275 to 363.8 nanometers and 408.9 to 686.1 nanometers, respectively. In the visible light spectral region, the lasers can produce up to 100 watts of continuous-wave power with the output concentrated into several strong lines (primarily the 488 and 514.5 nanometer transitions). The gain bandwidth on each transition is on the order of 2.5 gigahertz. Argon-ion gas laser discharge tubes have a useful life span ranging between 2000 and 5000 hours, and operate at gas pressures of approximately 0.1 torr.

An unfortunate side affect of the high discharge currents and low gas pressure employed by argon-ion lasers is an extremely high plasma electron temperature, which generates a significant amount of heat. In most cases, high power (2 to 100 watts) argon-ion laser systems are water-cooled through an external chiller, but lower power (5-150 milliwatts) models can be cooled with forced air through an efficient fan. Argon-ion lasers utilized in confocal and other fluorescence microscopy techniques are generally of the lower power variety, which produce between 10 and 100 milliwatts of power in TEM(00) mode at 488.0 nanometers. The laser cavity for these smaller systems is approximately 35 to 50 centimeters in length and about 15 centimeters in diameter, and can be housed in a small cabinet with an integral fan to supply fresh, cool air.

Contributing Authors

Kenneth R. Spring - Scientific Consultant, Lusby, Maryland, 20657.

Matthew Parry-Hill and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.