CO2 cutting lasers apply electrical excitation to a lasing medium by the use of resonator gases to add power and control to that energy. The lasing medium - CO2 - is stimulated by high energy electrical discharge. Nitrogen - is used to transfer energy to the CO2 by molecular excitement, adding power to the beam.
An unwanted by-product of these processes is heat, so another resonator gas - Helium – is used to act as a heat sink. From this process a laser beam is produced.