Molecular lasers
Gas lasers

Discovered by Patel shortly after lasers in the visible range (ruby, He-Ne), this laser operates on the vibration-rotation levels of the CO ₂ molecule. The latter has three vibrational modes (ν ₁ , ν ₂ and ν ₃ ), with, in each mode, vibrational levels in which the molecule can occupy one of the rotational levels (not shown in figure 4 ). Vibrational energy exchanges take place with high probability between the vibrational levels...