"The atoms become like a moth, seeking out the region of higher laser intensity."
Steven Chu, physicist
The carbon dioxide laser is considered the most useful and versatile type of laser. It was invented in 1964 by Kumar Patel (b. 1938) while he was working in the United States at Bell Laboratories, New Jersey.
Carbon dioxide lasers emit infrared radiation with a wavelength between 9 and 11 micrometers. The active medium in the laser is a mixture of carbon dioxide, nitrogen, and helium. The nitrogen molecules, made to vibrate by an electric current, cannot lose this energy by electron emission, so they in turn excite the carbon dioxide molecules, which produce the laser light. The helium plays two roles; it assists the transfer from the gas of heat caused by the electric discharge, and it helps the carbon dioxide molecules to return to their ground state after excitation. The gas mixture is generally contained in a sealed chamber, with a reflecting mirror of polished metal at one end and a partially transmitting one of coated zinc selenide at the other, through which the laser beam escapes.
Patel found many uses for his device. As a result, the carbon dioxide laser has more practical applications today than any other type of laser. It has improved high-resolution and saturation spectroscopy, contributed to laser-induced fusion and nonlinear optics, and is even used for the optical pumping that has made possible newer types of lasers.
