This is a helium neon laser I built back in 1994 out of junk parts I scrounged up. The picture shows the energized tube inside of the plastic pipe that I encased it in. lets just say that I was the first guy on the block with a laser pointer...
Step 1: Only Two Major Parts
At top is the laser tube that came out of an old hand held scanner and below is a 16KV power inverter that came out of an old broken IR scope.
Step 2: Various Views
Top left shows the C battery that powers it as well as the end cap I fabricated and the end of my plastic pipe housing where the battery goes.
Top right shows the "business" end with the protective red glass filter lens cap that I built to protect the laser tube's mirrored end.
Bottom left shows the beam on a piece of paper. It's not very bright because the laser tube actually requires 20KV to properly operate rather than the 16KV my power source is putting out. But at least you don't have to plug it in.
Bottom right is a view directly through the center of the tube.
Step 3: Finished Product
Here are views of the completed tube side, back power button, and "business end".
This is actually a very simple electrical project to assemble, the hardest part actually was making the containment tube. The only problem anyone would have trying to construct a duplicate would be finding the rather obscure old parts, particularly the power inverter.
Step 4: Schematic
This is the schematic...pretty simple.