Rami Arieli: "The Laser Adventure" Chapter 6, Carbon Dioxide Lasers page 1
6.1.6 Carbon-Dioxide (CO2) Laser

Lasing action in a CO2 molecule was first demonstrated by C. Patel in 1964.
He transmitted an electric discharge pulse through pure CO2 gas in a laser tube, and got a small laser output.

CO2 is the gas in which the lasing process occurs, but other gas additives to the laser tube improve the total efficiency of the laser.

The standard CO2 laser includes in the active medium a mixture of CO2 with N2 and He. The optimal proportion of these 3 gases in the mixture depends on the laser system and the excitation mechanism. In general, for a continuous wave laser the proportions are:

CO2:N2:He - 1:1:8

CO2 is a linear molecule, and the three atoms are situated on a straight line with the Carbon atom in the middle.

In figure 6.5 the three vibrational modes of CO2 molecule are illustrated:

  1. Symmetric stretch mode (n1).
  2. Bending mode (n2).
  3. Asymmetric stretch mode (n3).
 
Figure 6.5: Oscillation Modes of CO2 Molecule