A gas dynamic laser (GDL) is a laser based on differences in relaxation velocities of molecular vibrational states. The lasing medium gas has such properties that an energetically lower vibrational state relaxes faster than a higher vibrational state, and so a population inversion is achieved in a particular time. It was invented by Edward Gerry and Arthur Kantrowitz at Avco Everett Research Laboratory in 1966.[1]
Pure gas dynamic lasers usually use a combustion chamber, supersonic expansion nozzle, and CO2, in a mixture with nitrogen or helium, as the laser medium.
Gas dynamic lasers can be pumped by combustion or adiabatic expansion of gas. Any hot and compressed gas with appropriate vibrational structure could be utilized.
The explosively pumped gas dynamic laser is a version of GDL pumped by expansion of explosion products. Hexanitrobenzene and/or tetranitromethane with metal powder is the preferred explosive. This device could have very high pulsed peak power output suitable for laser weapons.