Gas lasers

Gas laser - a laser in which the active medium is a gas containing a laser active species. It is typically composed of a plasma discharge tube containing a gas that can be excited with an electric discharge.

Helium Neon lasers

Illuminated Neon signs are common and you would be right to assume therefore that it is the Neon gas in the laser that produces the light output. The addition of the Helium to the Neon gas increases the effectiveness of the laser by efficiently absorbing the energy of the electrons. A few thousand volts discharge is used, with a current of 10-20 milliamps.

The efficiency of a HeNe lasers is very low (< 1%) but as they are commonly used only in low power applications (several Milliwatts of energy) they can be cooled effectively by air.

Gas Ion lasers

Neon belongs to the inert group of elements known as the Noble gases. Other members of this group include Argon and Krypton. As with all gas lasers these can be ionised by a discharge of high energy electrons. These lasers need higher currents and so the laser design is more complicated. They are also water-cooled due to the large amount of waste heat generated.

A 200 Volt discharge is used, with a current of 15-50 Amps. Several Watts of energy can be produced for a continuous beam.

Carbon Dioxide lasers

The vibrational and rotational modes of the gas molecules is used, and infra-red microwave radiation is thus produced.

Upto 30 % efficiency can be achieved and it is easy to produce a beam of 100 Watts of energy. Using laser tubes tens of metres in length enable many kilowatts of energy to be produced.