I (Simon) have wanted to build a TEA laser ever since I heard about them years ago, so when I got a carboard build-your-own Wimshurst kit it came right to the top of my project list.
A very high voltage is applied instantaneously across two long electrodes. The nitrogen in the air gets excited, and a population inversion occurs fit for lasing. The discharge lasts around 1 nanosecond, and in that time a joule of electrical energy is discharged, giving about a millijoule of light output. While this isn’t very much, it does mean the laser outputs light at around 1 megawatt! The output is UV, so is only made visible by flourescence. We used tin foil and plastic sheeting for capacitors, a spark gap to quickly energise the electrodes, for which a couple of rulers were used. We fired the laser at a postit with some highlighter pen on:
Now for some great photos Mark took of the Wimshurst once I’d built the kit: