Carbon dioxide (CO2) lasers are one of the earliest and most widely used types of gas lasers. Gas lasers use an electric current discharged through a gas to emit light that is coherent. Laser light has a high degree of temporal and spatial coherence that cannot be attained any other way.
A carbon dioxide laser produces an infrared light. It is the highest-power continuous wave laser and one of the most efficient lasers available. Carbon dioxide lasers use an air or water-cooled discharge, which usually is made up of carbon dioxide, nitrogen, hydrogen and helium. Like all lasers, carbon dioxide lasers rely on population inversion to function. This occurs when a system of atoms or molecules has more members in an excited state.
Special materials are required for the construction of carbon dioxide lasers, because they operate in the infrared spectrum. Mirrors, windows and lenses are used to focus and amplify the light. The mirrors are silvered, and the windows and lenses are made of germanium. For higher-power applications, the mirrors are made of gold, and zinc selenide windows and lenses are used.
In their basic form, carbon dioxide lasers have a gas discharge with a total reflector at one end of the unit. At the output end is a reflective output coupler. Usually, the output coupler is a zinc selenide mirror.
Carbon dioxide lasers are capable of high power output yet are reasonable in cost, compared with other types of lasers. For this reason, CO2 lasers are popular for industrial applications such as cutting, welding and engraving. CO2 lasers are also useful for making devices from the common plastic poly, because it absorbs infrared light.
Another main application for carbon dioxide lasers is in surgical procedures. Most biological tissue is made up of water. Water absorbs this light frequency well. Some examples of medical uses are laser surgery, dermabrasion and laser resurfacing. Laser resurfacing is commonly known as a laser facelift, in which the skin is burned to promote collagen formation.
Carbon dioxide lasers are used to treat some skin conditions. In this application, the lasers remove bumps, podules and other skin formations that might be undesirable. Some radical and cutting-edge surgical applications have been tested, such as using C02 lasers to weld human tissue, thus eliminating the need for traditional sutures.
Laser resurfacing is also used in ophthalmology. The lens of the human eye can be resurfaced to correct vision. The procedure might also be used to treat certain types of diseases that affect the eyes.