Resonator Gases

The laser resonator gases for CO₂ lasers usually consist of a mixture of helium, nitrogen and carbon dioxide. Carbon dioxide (CO₂) is the gas which is active in generating the laser light itself, i.e. infrared radiation. The radiation is created by transitions between different vibrational energy levels in the carbon dioxide molecule. In this way it would be possible to run a CO₂ laser using only carbon dioxide as the laser gas. However, in order to reach the very high laser powers which are necessary for laser cutting and welding it is necessary to add nitrogen and helium to the laser gas.

The laser resonator gases for CO₂ lasers usually consist of a mixture of helium, nitrogen and carbon dioxide. There are a number of reasons for adding helium to the laser gas mixture:
1. Helium helps to remove CO₂ molecules from the lower laser level by speeding up relaxation ransitions.
2. Helium has a very high thermal conductivity. Helium then helps to conduct heat away from the electric discharge.
Helium is added in order to reach very high laser powers.

Impurities in the laser gas mixture can decrease the performance of a CO₂ laser by lowering the output power, making the electric discharge unstable or increasing the consumption of laser gases. The quality of the laser gases is not only decided by the purity as such but by what type of impurities they contain and in what levels. Therefore the use of BIP cylinders is advisable for reaching a longer life time of your resonator and mirrors.

The laser resonator gases for CO₂ lasers usually consist of a mixture of helium, nitrogen and carbon dioxide. By using an electric discharge it is very easy to excite a nitrogen molecule to its first vibrational energy level, which has almost the same energy as the upper laser level of CO₂.The vibrational energy is easily transferred from N₂ to CO₂ by collisions between the two molecules. Altogether it is far easier to excite the upper laser level of CO₂ by using nitrogen as an intermediate than to use only CO₂. Nitrogen is added in order to reach very high laser powers.

Impurities in the laser gas mixture can decrease the performance of a CO₂ laser by lowering the output power, making the electric discharge unstable or increasing the consumption of laser gases. The quality of the laser gases is not only decided by the purity as such but by what type of impurities they contain and in what levels. Therefore the use of BIP cylinders is advisable for reaching a longer life time of your resonator and mirrors.