 They can be used to detect explosives and chemical warfare agents, by the means of infrared spectroscopy or to evaluate the plasma densities by the means of interferometry techniques.FIR lasers typically consist of a long (1–3 meters) waveguide filled with gaseous organic molecules, optically pumped or via HV discharge.They are highly inefficient, often require helium cooling, high magnetic fields, and/or are only line tunable.