Gas Lasers

In these lasers the lasing medium is made-up of one or a mixture of gases or vapors. Gas lasers can be classified in terms of the type of transitions that lead to their operation: atomic or molecular. The most common of all gas lasers is the helium-neon (He-Ne) laser. The presence of two atomic species (helium and neon) in this gas laser might suggest that the medium is made of molecules, but these two species of atoms do not form a stable molecule. In fact, all inert atoms like helium, argon, krypton, etc. (those in the last column of the Periodic Table) hold tightly to their own electron clouds and seldom form a molecule or react with other atoms (hence the name: inert). In the He-Ne laser the transition that produces the output light is an atomic transition. Gas lasers that employ molecular gas or vapor for their lasing medium use molecular transitions for their lasing operation. Molecular transitions tend to be more complex than atomic ones. As a consequence the laser light produced by molecular lasers tends to have a wider and more varied collection of properties. Examples of some common molecular gas lasers are carbon monoxide (CO), carbon dioxide (CO2), excimer, and nitrogen (N2) lasers.