“The nitrogen laser will give 100kW pulses of light at 337.1nm (UVA light). The pulses are only 6ns long, so the energy per pulse is just 0.6mJ. It is a very simple laser, and it does not require mirrors or glass working at all! But using a mirror at one end of the laser will boost the output to over 250%. And if the nitrogen entering the laser (it is a flowing gas laser, but it can be made sealed) is cooled, it can go up to 120 pps. So if it is running at 120 pps, and has a mirror at one end, the average power output will be 180 mW. Although the beam is invisible it can be used to pump dye lasers to give beams with wavelengths ranging from infrared to ultraviolet.” Link.
The Homemade Nitrogen Laser