Lasers
HeNe | CO₂ | Argon Ion | Excimer

One of the most popular lasers for laser light shows is the Argon Ion laser, since it has several visible lines (in the green & blue regions) that can be selected with a diffraction grating or prism.

Two Argon Ion lasers were worked on at the college in the Summer of 2003, one of which was a Coherent Innova-90 laser, which is basically an all-in-one package. Work done on this laser was basic (and preventative) maintenance, such as cleaning out the water lines periodically to make sure there wasn't too much buildup on the cooling lines inside the power supply and laser head. Also, the laser needed to be run for an hour or so (at low currents) about once a week to keep the pressures low in the tube. This needs to be done mainly because of molecules that become embedded in the cathode of the laser, over time these molecules release thereby raising the pressure of the tube. If the tube pressure raises too much, the power supply will not be able to start the laser (since the operating power will not be sufficient to produce a discharge).
A picture of this laser operating is shown below.

Another laser that was worked on over the summer was quite different from the Coherent model shown above; this laser comes out of a high-speed photocopier, and was purchased on the surplus market. This laser came 'as-is' and needed a lot of work; basically the entire laser was covered in baked-on toner from the copier, an unknown gas mix (we weren't sure if the mix was correct anymore), no power supply, and the optics weren't lined up.
This laser was worked on by a few student workers over the summer; here is a picture of the laser after it was cleaned.

As you can see, this is a very simple Argon laser, there is no room for an etalon or any other types of wavelength selector equipment inside the cavity. This is a typical photocopier laser, the optics were aligned once (with an open-ended wrench!) and bolted into the machine (hopefully) never to be touched again. The brewster-angled windows can be seen at each end of the tube. The above picture was taken while the laser's optics were being aligned.