A CO2 laser is a pumped laser whose pump energy is generated electrically via a gas discharge using direct current, alternating current, or radio frequency. The discharge excites nitrogen molecules and sets them to a weak vibrational level, transferring their excitation energy upon impact with carbon dioxide molecules. Helium serves to discharge the lower laser level and dissipate the heat. Other components such as hydrogen or water vapor ensure that the carbon monoxide oxidizes back to carbon dioxide.
CO2 lasers emit in the long-wave infrared region at a wavelength of 10.6 µm, or at wavelengths in the 9 µm to 11 µm range. In most cases, average powers range from tens of watts to many kilowatts. More than 10 % of the pump power of CO2 lasers is converted into laser power. This value is higher than that of semiconductor lasers.